Quiz chapter 16 (2)

अब Quizwiz के साथ अपने होमवर्क और परीक्षाओं को एस करें!

15-38 Which of the following statements about vesicle budding from the Golgi is false? (a) Clathrin molecules are important for binding to and selecting cargoes for transport. (b) Adaptins interact with clathrin. (c) Once vesicle budding occurs, clathrin molecules are released from the vesicle. (d) Clathrin molecules act at the cytosolic surface of the Golgi membrane.

(a) Clathrin molecules are important for binding to and selecting cargoes for transport.

A growing microtubule has

(a) GTP bound to the β-tubulin subunits at the microtubule end.

15-2 Which of the following statements about membrane-enclosed organelles is true? (a) In a typical cell, the area of the endoplasmic reticulum membrane far exceeds the area of plasma membrane. (b) The nucleus is the only organelle that is surrounded by a double membrane. (c) Other than the nucleus, most organelles are small and thus, in a typical cell, only about 10% of a cell's volume is occupied by membrane- enclosed organelles; the other 90% of the cell volume is the cytosol. (d) The nucleus is the only organelle that contains DNA.

(a) In a typical cell, the area of the endoplasmic reticulum membrane far exceeds the area of plasma membrane.

15-14 What is the role of the nuclear localization sequence in a nuclear protein? (a) It is bound by cytoplasmic proteins that direct the nuclear protein to the nuclear pore. (b) It is a hydrophobic sequence that enables the protein to enter the nuclear membranes. (c) It aids in protein unfolding so that the protein can thread through nuclear pores. (d) It prevents the protein from diffusing out of the nucleus through nuclear pores.

(a) It is bound by cytoplasmic proteins that direct the nuclear protein to the nuclear pore.

15-21 Which of the following statements about peroxisomes is false? (a) Most peroxisomal proteins are synthesized in the ER. (b) Peroxisomes synthesize phospholipids for the myelin sheath. (c) Peroxisomes produce hydrogen peroxide. (d) Vesicles that bud from the ER can mature into peroxisomes.

(a) Most peroxisomal proteins are synthesized in the ER.

Which of the following statements about the cell cycle is false? • (a) Once a cell decides to enter the cell cycle, the time from start to finish is the same in all eucaryotic cells. • (b) An unfavorable environment can cause cells to arrest in G1. • (c) A cell has more DNA during G2 than it did in G1. • (d) The cleavage divisions that occur in an early embryo have short G1 and G2 phases.

(a) Once a cell decides to enter the cell cycle, the time from start to finish is the same in all eucaryotic cells.

15-61 Which of the following statements about phagocytic cells in animals is false? (a) Phagocytic cells are important in the gut to take up large particles of food. (b) Phagocytic cells scavenge dead and damaged cells and cell debris. (c) Phagocytic cells can engulf invading microorganisms and deliver them to their lysosomes for destruction. (d) Phagocytic cells extend pseudopods that surround the material to be ingested.

(a) Phagocytic cells are important in the gut to take up large particles of food.

15-45 N-linked oligosaccharides on secreted glycoproteins are attached to ________. (a) nitrogen atoms in the polypeptide backbone. (b) the serine or threonine in the sequence Asn-X-Ser/Thr. (c) the N-terminus of the protein. (d) the asparagine in the sequence Asn-X-Ser/Thr.

(d) the asparagine in the sequence Asn-X-Ser/Thr.

Both multicellular plants and animals have _____________________.

(d) tissues composed of multiple different cell types

15-56 Which of the following statements about secretion is true? (a) The membrane of a secretory vesicle will fuse with the plasma membrane when it discharges its contents to the cell's exterior. (b) Vesicles for regulated exocytosis will not bud off the trans Golgi network until the appropriate signal has been received by the cell. (c) The signal sequences of proteins destined for constitutive exocytosis ensure their packaging into the correct vesicles. (d) Proteins destined for constitutive exocytosis aggregate as a result of the acidic pH of the trans Golgi network.

(a) The membrane of a secretory vesicle will fuse with the plasma membrane when it discharges its contents to the cell's exterior.

Acetylcholine binds to a G protein coupled receptor (GPCR) on heart muscle, making the heart beat more slowly. The activated receptor stimulates a G protein, which opens a K+ channel in the plasma membrane, as shown in the figure. Which of the following would enhance this effect of the acetylcholine?

(a) addition of a high concentration of a non-hydrolyzable analog of GTP that cannot be converted to GDP

15-31 Figure Q15-31 shows the organization of a protein that resides on the ER membrane. The N- and C-termini of the protein are labeled. Boxes 1, 2, and 3 represent membrane-spanning sequences. Non-membrane-spanning regions of the protein are labeled "X," "Y," and "Z." Once this protein is fully translocated, where will region Y be? (a) in the cytoplasm (b) in the ER lumen (c) inserted into the ER membrane (d) degraded by signal peptidase

(a) in the cytoplasm

15-12 Proteins that are fully translated in the cytosol and lack a sorting signal will end up in ____. (a) the cytosol. (b) the mitochondria. (c) the interior of the nucleus. (d) the nuclear membrane.

(a) the cytosol.

15-20 Which of the following statements about transport into mitochondria and chloroplasts is false? (a) The signal sequence on proteins destined for these organelles is recognized by a receptor protein in the outer membrane of these organelles. (b) After a protein moves through the protein translocator in the outer membrane of these organelles, the protein diffuses in the lumen until it encounters a protein translocator in the inner membrane. (c) Proteins that are transported into these organelles are unfolded as they are being transported. (d) Signal peptidase will remove the signal sequence once the protein has been imported into these organelles.

(b) After a protein moves through the protein translocator in the outer membrane of these organelles, the protein diffuses in the lumen until it encounters a protein translocator in the inner membrane.

You create cells with a version of Cdc6 that cannot be phosphorylated and thus cannot be degraded. Which of the following statements describes the likely consequence of this change in Cdc6?

(b) Cells will be unable to complete DNA synthesis.

15-18 Your friend works in a biotechnology company and has discovered a drug that blocks the ability of Ran to exchange GDP for GTP. What is the most likely effect of this drug on nuclear transport? (a) Nuclear transport receptors would be unable to bind cargo. (b) Nuclear transport receptors would be unable to enter the nucleus. (c) Nuclear transport receptors would be unable to release their cargo in the nucleus. (d) Nuclear transport receptors would interact irreversibly with the nuclear pore fibrils.

a diploid cell containing 32 chromosomes will make a haploid cell containing ___ chromosomes

15-64 You are working in a biotech company that has discovered a small-molecule drug called H5434. H5434 binds to LDL receptors when they are bound to cholesterol. H5434 binding does not alter the conformation of the LDL receptor's intracellular domain. Interestingly, in vitro experiments demonstrate that addition of H5434 increases the affinity of LDL for cholesterol and prevents cholesterol from dissociating from the LDL receptor even in acidic conditions. Which of the following is a reasonable prediction of what may happen when you add H5434 to cells? (a) Cytosolic cholesterol levels will remain unchanged relative to normal cells. (b) Cytosolic cholesterol levels will decrease relative to normal cells. (c) The LDL receptor will remain on the plasma membrane. (d) The uncoating of vesicles will not occur.

(b) Cytosolic cholesterol levels will decrease relative to normal cells.

15-51 Which of the following statements about the protein quality control system in the ER is false? (a) Chaperone proteins help misfolded proteins fold properly. (b) Proteins that are misfolded are degraded in the ER lumen. (c) Protein complexes are checked for proper assembly before they can exit the ER. (d) A chaperone protein will bind to a misfolded protein to retain it in the ER.

(b) Proteins that are misfolded are degraded in the ER lumen.

15-1 Which of the following statements about the endoplasmic reticulum (ER) is false? (a) The ER is the major site for new membrane synthesis in the cell. (b) Proteins to be delivered to the ER lumen are synthesized on smooth ER. (c) Steroid hormones are synthesized on the smooth ER. (d) The ER membrane is contiguous with the outer nuclear membrane.

(b) Proteins to be delivered to the ER lumen are synthesized on smooth ER.

15-34 Figure Q15-34 shows the organization of a protein that normally resides in the plasma membrane. The boxes labeled 1 and 2 represent membrane-spanning sequences and the arrow represents a site of action of signal peptidase. Given this diagram, which of the following statements must be true? (a) The N-terminus of this protein is cytoplasmic. (b) The C-terminus of this protein is cytoplasmic. (c) The mature version of this protein will span the membrane twice, with both the N- and C-terminus in the cytoplasm. (d) None of the above.

(b) The C-terminus of this protein is cytoplasmic.

15-8 Which of the following statements is true? (a) Lysosomes are believed to have originated from the engulfment of bacteria specialized for digestion. (b) The nuclear membrane is thought to have arisen from the plasma membrane invaginating around the DNA. (c) Because bacteria do not have mitochondria, they cannot produce ATP in a membrane-dependent fashion. (d) Chloroplasts and mitochondria share their DNA.

(b) The nuclear membrane is thought to have arisen from the plasma membrane invaginating around the DNA.

15-39 Molecules to be packaged into vesicles for transport are selected by ________. (a) clathrin. (b) adaptins. (c) dynamin. (d) SNAREs.

(b) adaptins.

Cells that are terminally differentiated ______________________.

(b) can no longer undergo cell division

15-42 An individual transport vesicle ________. (a) contains only one type of protein in its lumen. (b) will fuse with only one type of membrane. (c) is endocytic if it is traveling toward the plasma membrane. (d) is enclosed by a membrane with the same lipid and protein composition as the membrane of the donor organelle.

(b) will fuse with only one type of membrane.

15-52 Which of the following statements about the unfolded protein response (UPR) is false? (a) Activation of the UPR results in the production of more ER membrane. (b) Activation of the UPR results in the production of more chaperone proteins. (c) Activation of the UPR occurs when receptors in the cytoplasm sense misfolded proteins. (d) Activation of the UPR results in the cytoplasmic activation of gene regulatory proteins.

15-19 Which of the following statements is true? (a) The signal sequences on mitochondrial proteins are usually at the C- terminus. (b) Most mitochondrial proteins are not imported from the cytosol but are synthesized inside the mitochondria. (c) Chaperone proteins in the mitochondria facilitate the movement of proteins across the outer and inner mitochondrial membranes. (d) Mitochondrial proteins cross the membrane in their native, folded state.

(c) Chaperone proteins in the mitochondria facilitate the movement of proteins across the outer and inner mitochondrial membranes.

15-15 Which of the following statements about nuclear transport is true? (a) mRNAs and proteins transit the nucleus through different types of nuclear pores. (b) Nuclear import receptors bind to proteins in the cytosol and bring the proteins to the nuclear pores, where the proteins are released from the receptors into the pores for transit into the nucleus. (c) Nuclear pores have water-filled passages that small, water-soluble molecules can pass through in a nonselective fashion. (d) Nuclear pores are made up of many copies of a single protein.

(c) Nuclear pores have water-filled passages that small, water-soluble molecules can pass through in a nonselective fashion.

15-29 Which of the following statements is true? (a) Proteins destined for the ER are translated by a special pool of ribosomes whose subunits are always associated with the outer ER membrane. (b) Proteins destined for the ER translocate their associated mRNAs into the ER lumen where they are translated. (c) Proteins destined for the ER are translated by cytosolic ribosomes and are targeted to the ER when a signal sequence emerges during translation. (d) Proteins destined for the ER are translated by a pool of cytosolic ribosomes that contain ER-targeting sequences that interact with ER- associated protein translocators.

(c) Proteins destined for the ER are translated by cytosolic ribosomes and are targeted to the ER when a signal sequence emerges during translation

15-43 Which of the following statements about vesicular membrane fusion is false? (a) Membrane fusion does not always immediately follow vesicle docking. (b) The hydrophilic surfaces of membranes have water molecules associated with them that must be displaced before vesicle fusion can occur. (c) The GTP hydrolysis of the Rab proteins provides the energy for membrane fusion. (d) The interactions of the v-SNAREs and the t-SNAREs pull the vesicle membrane and the target organelle membrane together so that their lipids can intermix.

15-48 Cells have oligosaccharides displayed on their cell surface that are important for cell-cell recognition. Your friend discovered a transmembrane glycoprotein, GP1, on a pathogenic yeast cell that is recognized by human immune cells. He decides to purify large amounts of GP1 by expressing it in bacteria. To his purified protein he then adds a branched 14-sugar oligosaccharide to the asparagine of the only Asn-X-Ser sequence found on GP1 (Figure Q15-48). Unfortunately, immune cells do not seem to recognize this synthesized glycoprotein. Which of the following statements is a likely explanation for this problem? (a) The oligosaccharide should have been added to the serine instead of the asparagine. (b) The oligosaccharide should have been added one sugar at a time. (c) The oligosaccharide needs to be further modified before it is mature. (d) The oligosaccharide needs a disulfide bond.

15-57 Given this diagram, which of the following statements is true? (a) When this vesicle fuses with the plasma membrane, the entire Krt1 protein will be secreted into the extracellular space. (b) When this vesicle fuses with the plasma membrane, the C-terminus of Krt1 will be inserted into the plasma membrane. (c) When this vesicle fuses with the plasma membrane, the N-terminus of Krt1 will be in the extracellular space. (d) When this vesicle fuses with the plasma membrane, the N-terminus of Krt1 will be cytoplasmic.

The growth factor Superchick stimulates the proliferation of cultured chicken cells. The receptor that binds Superchick is a receptor tyrosine kinase (RTK), and many chicken tumor cell lines have mutations in the gene that encodes this receptor. Which of the following types of mutation would be expected to promote uncontrolled cell proliferation? • (a) a mutation that prevents dimerization of the receptor • (b) a mutation that destroys the kinase activity of the receptor • (c) a mutation that inactivates the protein tyrosine phosphatase that normally removes the phosphates from tyrosines on the activated receptor • (d) a mutation that prevents the binding of the normal extracellular signal to the receptor

(c) a mutation that inactivates the protein tyrosine phosphatase that normally removes the phosphates from tyrosines on the activated receptor

The figure shows how normal signaling works with a Ras protein acting downstream of an RTK. You examine a cell line with a constitutively active Ras protein that is always signaling. Which of the following conditions will turn off signaling in this cell line?

15-23 Most proteins destined to enter the endoplasmic reticulum _________. (a) are transported across the membrane after their synthesis is complete. (b) are synthesized on free ribosomes in the cytosol. (c) begin to cross the membrane while still being synthesized. (d) remain within the endoplasmic reticulum.

15-54 Vesicles from the ER enter the Golgi at the ______. (a) medial cisternae. (b) trans Golgi network. (c) cis Golgi network. (d) trans cisternae.

15-41 Your friend has just joined a lab that studies vesicle budding from the Golgi and has been given a cell line that does not form mature vesicles. He wants to start designing some experiments but wasn't listening carefully when he was told about the molecular defect of this cell line. He's too embarrassed to ask and comes to you for help. He does recall that this cell line forms coated pits but vesicle budding and the removal of coat proteins don't happen. Which of the following proteins might be lacking in this cell line? (a) clathrin (b) Rab (c) dynamin (d) adaptin

15-13 Signal sequences that direct proteins to the correct compartment are _________. (a) added to proteins through post-translational modification. (b) added to a protein by a protein translocator. (c) encoded in the amino acid sequence and sufficient for targeting a protein to its correct destination. (d) always removed once a protein is at the correct destination.

The concentration of mitotic cyclin (M cyclin) ________________.

15-25 In which cellular location would you expect to find ribosomes translating mRNAs that encode ribosomal proteins? (a) the nucleus (b) on the rough ER (c) in the cytosol (d) in the lumen of the ER

A protein kinase can act as an integrating device in signaling if it

15-6 Which of the following organelles is not part of the endomembrane system? (a) Golgi apparatus (b) the nucleus (c) mitochondria (d) lysosomes

15-47 Which of the following statements about disulfide bond formation is false? (a) Disulfide bonds do not form under reducing environments. (b) Disulfide bonding occurs by the oxidation of pairs of cysteine side chains on the protein. (c) Disulfide bonding stabilizes the structure of proteins. (d) Disulfide bonds form spontaneously within the ER because the lumen of the ER is oxidizing.

(d) Disulfide bonds form spontaneously within the ER because the lumen of the ER is oxidizing.

15-36 Which of the following choices reflects the appropriate order of locations through which a protein destined for the plasma membrane travels? (a) lysosome ! endosome ! plasma membrane (b) ER ! lysosome ! plasma membrane (c) Golgi ! lysosome ! plasma membrane (d) ER ! Golgi ! plasma membrane

(d) ER ! Golgi ! plasma membrane

Akt promotes the survival of many cells. It is activated by an intracellular signaling pathway that is triggered by a receptor tyrosine kinase (RTK) that activates PI 3-kinase. • • Which of the following statements is false? • (a) In the presence of a survival signal, Akt localizes to the plasma membrane by binding to PIP3. • (b) In the absence of survival signal, Bad inhibits the cell death inhibitor protein Bcl2. • (c) In the presence of survival signal, the cell death inhibitory protein Bcl2 is active. • (d) In the absence of survival signal, Bad is phosphorylated.

(d) In the absence of survival signal, Bad is phosphorylated.

15-49 Different glycoproteins can have a diverse array of oligosaccharides. Which of the statements below about this diversity is true? (a) Extensive modification of oligosaccharides occurs in the extracellular space. (b) Different oligosaccharides are covalently linked to proteins in the ER and the Golgi. (c) A diversity of oligosaccharyl transferases recognizes specific protein sequences, resulting in the linkage of a variety of oligosaccharides to proteins. (d) Oligosaccharide diversity comes from modifications that occur in the ER and the Golgi of the 14-sugar oligosaccharide added to the protein in the ER.

(d) Oligosaccharide diversity comes from modifications that occur in the ER and the Golgi of the 14-sugar oligosaccharide added to the protein in the ER.

15-27 You are interested in Fuzzy, a soluble protein that functions within the ER lumen. Given that information, which of the following statements must be true? (a) Fuzzy has a C-terminal signal sequence that binds to SRP. (b) Only one ribosome can be bound to the mRNA encoding Fuzzy during translation. (c) Fuzzy must contain a hydrophobic stop-transfer sequence. (d) Once the signal sequence from Fuzzy has been cleaved, the signal peptide will be ejected into the ER membrane and degraded.

(d) Once the signal sequence from Fuzzy has been cleaved, the signal peptide will be ejected into the ER membrane and degraded.

15-28 Which of the following statements about a protein in the lumen of the ER is false? (a) A protein in the lumen of the ER is synthesized by ribosomes on the ER membrane. (b) Some of the proteins in the lumen of the ER can end up in the extracellular space. (c) Some of the proteins in the lumen of the ER can end up in the lumen of an organelle in the endomembrane system. (d) Some of the proteins in the lumen of the ER can end up in the plasma membrane.

(d) Some of the proteins in the lumen of the ER can end up in the plasma membrane.

15-40 Which of the following protein families are not involved in directing transport vesicles to the target membrane? (a) SNAREs (b) Rabs (c) tethering proteins (d) adaptins

(d) adaptins

15-24 After isolating the rough endoplasmic reticulum from the rest of the cytoplasm, you purify the RNAs attached to it. Which of the following proteins do you expect the RNA from the rough endoplasmic reticulum to encode? (a) soluble secreted proteins (b) ER membrane proteins (c) plasma membrane proteins (d) all of the above

(d) all of the above

15-10 Where are proteins in the chloroplast synthesized? (a) in the cytosol (b) in the chloroplast (c) on the endoplasmic reticulum (d) in both the cytosol and the chloroplast

(d) in both the cytosol and the chloroplast

If the isotope 32S has 16 protons and 16 neutrons, how many protons, neutrons, and electrons will the isotope 35S have, respectively?

16, 19, 16

15-11 Proteins that are fully translated in the cytosol do not end up in _______. (a) the cytosol. (b) the mitochondria. (c) the interior of the nucleus. (d) transport vesicles.

(d) transport vesicles.

Name a connective tissue.

- Bone - Tendon - Dermis of the skin - Cartilage

Typical folded proteins have a stability ranging from 7 to 15 kcal/mole at 37°C. Stability is a measure of the equilibrium between the folded (F) and unfolded (U) forms of the protein, with the unfolded form having a greater free energy (see Figure). For a protein with a stability of 7.1 kcal/mole, calculate the fraction of protein that would be unfolded (U) at equilibrium at 37°C. The equilibrium constant (Keq) is related to the free energy (ΔG°) by the equation Keq = 10-ΔG°/1.42.

1 in 100,000 is unfolded (K=10-5)

these monomeric GTP binding proteins are aided by two sets of regulatory proteins which are --------and-----

1) guanine nucleotide exchange factors (GEFs) activate the switch proteins by promoting the exchange of GDP and GTP (switch on) GTPase activating proteins (GAPs) turn them off by promoting GTP hydrolysis (switch off)

two main types of GTP binding proteins participate in intracellular signalling pathways which are --------and-----

1) large, trimeric GTP binding proteins (also called G-proteins) which relay messages from GPCR 2) small monomeric GTPase to help relay their signals

what determines the response of a cell to a signal?

1) presence or absence of the receptor 2) presence or absence of intracellular signaling molecules and intracellular effector proteins -lead to change in gene expression, metabolism, movement, shape, status 3) combinations of signals give different responses

two main types of protein kinases operate in intracellular signalling pathways: the most common are -------

1) serine/threonine kinases (phosphorylate proteins on serines or threonine. 2) tyrosine kinases (phosphorylate proteins on tyrosine

a typical path of reactions would follow which sequence? 1)binding of a hormone to a receptor 2) synthesis of cyclic AMP 3)phosphorylation of the target enzyme 4) release of a G protein from the interior cell membrane 5) activation of a protein kinase

1,4,2,5,3

on average, eukaryotic cells are ___ times longer and have ___ times more volume than prokaryotic cells

10, 1000

There are two properties of phospholipids that affect how tightly they pack together: the length of the hydrocarbon chain and the number of double bonds. The degree of packing, in turn, influences the relative mobility of these molecules in the membrane. Which of the following would yield the most highly mobile phospholipid (listed as number of carbons and number of double bonds, respectively)?

15 carbons with 2 double bonds

15-30 Match the components involved with ER transport with the appropriate cellular location. Locations can be used more than once, or not at all. Components Location 1. signal-recognition particle _____ 2. protein translocator _____ 3. mRNA _____ 4. SRP receptor _____ 5. active site of signal peptidase ____ A. cytosol B. ER lumen C. ER membrane

1—A; 2—C; 3—A; 4—C; 5—B

How many replication forks are formed when an origin of replication is opened?

calmodulin has a dumbbell shape with two globular ends connected by a long helix. each end has ____ Ca2+ binding domains.

16-3 Rank the following types of cell signaling from 1 to 4, with 1 representing the type of signaling in which the signal molecule travels the least distance and 4 the type of signaling in which the signal molecule travels the largest distance. ______ paracrine signaling ______ contact-dependent signaling ______ neuronal signaling ______ endocrine signaling

2 1 3 4

Water molecules readily form hydrogen bonds with other polar molecules, and when they encounter nonpolar molecules they must form hydrogen-bonding networks with neighboring water molecules. Which of the following molecules will cause a "cage" of water to form?

2-methylpropane

when a GCPR binds an extracellular signal, an intracellular G protein, composed of ______ subunits becomes activated: ____ of the G protein subunits are tethered to the plasma membrane by short lipid tails. When unstimulated, the a subunit is bound to ____ which is exchanged for ____ on stimulation. the intrinsic ____ activity of the a subunit is important for inactivating the G protein. ______ inhibits this activity of the a subunit thereby keeping the subunit in an active state

3 protein 30 + 2 GDP GTP GTPase cholera toxin

Given the sequence of one strand of a DNA helix (below), provide the sequence of the complementary strand and label the 5′ and 3′ ends. 5'-GCATTCGTGGGTAG-3'

3'-CGTAAGCACCCATC-5'

Hershey and Chase used radiolabeled macromolecules to identify the material that contains heritable information. What radioactive material was used to track DNA during this experiment?

32 P

The human genome is divided into linear segments and packaged into structures called chromosomes. What is the total number of chromosomes found in each of the somatic cells in your body?

which of the following DNA strands can form a DNA duplex by pairing with itself at each position?

5' - AAGCGCTT - 3'

Of the following choices, in a DNA helix, the complimentary strand for the following sequence is: 5' GCATTCGTGGGTAG 3'

5' CTACCCACGAATGC 3'

18-39 Name the stage of M phase in which the following events occur. Place the numbers 1-8 next to the letter headings to indicate the normal order of events. A. alignment of the chromosomes at the spindle equator B. attachment of spindle microtubules to chromosomes C. breakdown of nuclear envelope D. pinching of cell in two E. separation of two centrosomes and initiation of mitotic spindle assembly F. re-formation of the nuclear envelope G. condensation of the chromosomes H. separation of sister chromatids

5, metaphase 4, prometaphase 3, prometaphase 8, cytokinesis 2, prophase 7, telophase 1, prophase 6, anaphase

Which of the following molecules of RNA would you predict to be the most likely to fold into a specific structure as a result of intramolecular base-pairing?

5′-CCCUAAAAAAAAAAAAAAUUUUUUUUUUUUUUAGGG-3′

Larger molecules have hydrogen-bonding networks that contribute to specific, high-affinity binding. Smaller molecules such as urea can also form these networks. How many hydrogen bonds can urea (Figure below) form if dissolved in water?

GPCRS all have similar structures with --------transmembrane domains. when a GPCR binds an extracellular signal, an intracellular G proteins composed of ---------subunits, becomes activated. --------of the G-proteins are tethered to the plasma membrane by short lipid tails. when unstimulated, the alpha subunit is bound to --------which is exchanged for -------on stimulation. the intrinsic --------activity of the alpha subunit is important for inactivating the G-protein. --------inhibits this activity of the alpha subunit, thereby keeping the subunit in an active state.

7 3 2 GDP GTP GTPase cholera

A particular hormone is discovered to induce its effects by binding to surface proteins of receptor cells rather than passing through the membrane and activating intracellular receptors. This hormone is most likely which of the following types? a) peptide hormone b) steroid hormone c) hydrophilic hormone d) The answer cannot be determined with the given information.

A protein's functions are inhibited by a kinase. They activated by a phosphatase. Respectively, what are the actions of the kinase and phosphatase? a) phosphorylation, dephosphorylation b) dephosphorylation, phosphorylation c) Lower the system's overall kinetic energy, Increase the system's overall potential energy d) Increase the system's overall kinetic energy, Decrease the system's overall potential energy

All of the following are known to be part of a signal transduction cascade EXCEPT (A) phosphorylation of fibronectin (B) dissociation of the components of a heterotrimeric G-protein (C) enzymatic breakdown of phosphatidyl inositol bisphosphate (PIP2 ) (D) elevation of intracellular [Ca2+] (E) activation of cGMP phosphodiesterase

Consider a protein that contains an ER signal sequence at its N-terminus and a nuclear localization sequence in its middle. What would be the most likely fate of this protein? a) The protein would be translocated into the ER. b) The protein would be transported into the nucleus. c) The protein would remain in the cytoplasm. d) The protein would become part of the nuclear pore complex. e) The protein would be degraded.

MicroRNAs ____________________. A) are produced from a precursor miRNA transcript B) can degrade RNAs by using their intrinsic catalytic activity

The extent of complementarity of a miRNA with its target mRNA determines ________________. A) Whether the mRNA will be degraded by a nuclease within the RISC or transported elsewhere in the cell for degradation. B) Whether the mRNA will be transported to the nucleus. C) Whether RISC is degraded. D) Whether the miRNA synthesizes a complementary strand.

Transcription is similar to DNA replication in that ___________________. A) nucleotide polymerization occurs only in the 5′-to-3′ direction B) an RNA transcript is synthesized discontinuously and the pieces are then joined together

Which of the following is TRUE? a) Akt is a kinase b) Akt is a phosphatase c) Viagra inhibits PI-3 kinase signaling d) The NO receptor translocates to the nucleus after binding NO, like other steroid recptors. e) PI-3 kinase inhibitors would increase erections

Which of the following is used to treat flunitrazepam overdoses? a) Romazicon, a benzodiazepine receptor antagonist b) BNZ2 agonists such as Clorazepate c) GABA d) Carisoprodol, a muscle relaxant e) All of the above would make the effects of flunitrazepam worse.

Which of the following statements about molecular switches is false? (a) Phosphatases remove the phosphate from GTP on GTP-binding proteins, turning them off. (b) Protein kinases transfer the terminal phosphate from ATP onto a protein. (c) Serine/threonine kinases are the most common types of protein kinase. (d) A GTP-binding protein exchanges its bound GDP for GTP to become activated.

Which of the following statements about the Lac operon is false? A) The Lac repressor binds when lactose is present in the cell. B) Even when the CAP activator is bound to DNA, if lactose is not present, the Lac operon will not be transcribed. C) The CAP activator can only bind DNA when it is bound to cAMP. D) The Lac operon only produces RNA when lactose is present and glucose is absent.

You are interested in cell-size regulation and discover that signaling through a GPCR called ERC1 is important in controlling cell size in embryonic rat cells. The G protein downstream of ERC1 activates adenylyl cyclase, which ultimately leads to the activation of PKA. You discover that cells that lack ERC1 are 15% smaller than normal cells, while cells that express a mutant, constitutively activated version of PKA are 15% larger than normal cells. Given these results, which of the following treatments to embryonic rat cells should lead to smaller cells? (a) addition of a drug that causes cyclic AMP phosphodiesterase to be hyperactive (b) addition of a drug that prevents GTP hydrolysis by Gα (c) addition of a drug that activates adenylyl cyclase (d) addition of a drug that mimics the ligand of ERC1

do you expect garlic to improve erections? a) Yes b) No c) There is no reason to think it will have any effect at all

Which of the following statements about vesicle budding from the Golgi is false? (a) Clathrin molecules are important for binding to and selecting cargoes for transport. (b) Adaptins interact with clathrin. (c) Once vesicle budding occurs, clathrin molecules are released from the vesicle. (d) Clathrin molecules act at the cytosolic surface of the Golgi membrane.

A (cargo binds to cargo receptors. Adaptin molecules capture cargo receptors, which bind to the appropriate cargo molecules for incorporation into the vesicle)

Which of the following statements about membrane-enclosed organelles is true? (a) In a typical cell, the area of the endoplasmic reticulum membrane far exceeds the area of plasma membrane. (b) The nucleus is the only organelle that is surrounded by a double membrane. (c) Other than the nucleus, most organelles are small and thus, in a typical cell, only about 10% of a cell's volume is occupied by membrane-enclosed organelles; the other 90% of the cell volume is the cytosol. (d) The nucleus is the only organelle that contains DNA.

A (in a typical cell, the area of the endoplasmic reticulum membrane far exceeds the area of plasma membrane)

Figure Q15-31 shows the organization of a protein that resides on the ER membrane. The N- and C-termini of the protein are labeled. Boxes 1, 2, and 3 represent membrane-spanning sequences. Non-membrane-spanning regions of the protein are labeled "X," "Y," and "Z." Figure Q15-31 Once this protein is fully translocated, where will region Y be? (a) in the cytoplasm (b) in the ER lumen (c) inserted into the ER membrane (d) degraded by signal peptidase

A (in the cytoplasm)

What is the role of the nuclear localization sequence in a nuclear protein? (a) It is bound by cytoplasmic proteins that direct the nuclear protein to the nuclear pore. (b) It is a hydrophobic sequence that enables the protein to enter the nuclear membranes. (c) It aids in protein unfolding so that the protein can thread through nuclear pores. (d) It prevents the protein from diffusing out of the nucleus through nuclear pores.

A (it is bound by cytoplasmic proteins that direct the nuclear protein to the nuclear pore)

Which of the following statements about peroxisomes is false? (a) Most peroxisomal proteins are synthesized in the ER. (b) Peroxisomes synthesize phospholipids for the myelin sheath. (c) Peroxisomes produce hydrogen peroxide. (d) Vesicles that bud from the ER can mature into peroxisomes.

A (most peroxisomal proteins are synthesized in the ER)

Which of the following statements about phagocytic cells in animals is false? (a) Phagocytic cells are important in the gut to take up large particles of food. (b) Phagocytic cells scavenge dead and damaged cells and cell debris. (c) Phagocytic cells can engulf invading microorganisms and deliver them to their lysosomes for destruction. (d) Phagocytic cells extend pseudopods that surround the material to be ingested.

A (phagocytic cells are important in the gut to take up large particles of food)

A large protein that passes through the nuclear pore must have an appropriate _________. (a) sorting sequence, which typically contains the positively charged amino acids lysine and arginine. (b) sorting sequence, which typically contains the hydrophobic amino acids leucine and isoleucine. (c) sequence to interact with the nuclear fibrils. (d) Ran-interacting protein domain.

A (sorting sequence, which typically contains the positively charged amino acids lysine and arginine)

Proteins that are fully translated in the cytosol and lack a sorting signal will end up in ____. (a) the cytosol. (b) the mitochondria. (c) the interior of the nucleus. (d) the nuclear membrane.

A (the cytosol)

Which of the following statements about secretion is true? (a) The membrane of a secretory vesicle will fuse with the plasma membrane when it discharges its contents to the cell's exterior. (b) Vesicles for regulated exocytosis will not bud off the trans Golgi network until the appropriate signal has been received by the cell. (c) The signal sequences of proteins destined for constitutive exocytosis ensure their packaging into the correct vesicles. (d) Proteins destined for constitutive exocytosis aggregate as a result of the acidic pH of the trans Golgi network.

A (the membrane of a secretory vesicle will fuse with the plasma membrane when it discharges its contents to the cells exterior)

. ____________ are intermediate filaments?

Nuclear lamins

18-49 Consider an animal cell that has eight chromosomes (four pairs of homologous chromosomes) in G1 phase. How many of each of the following structures will the cell have at mitotic prophase? A. sister chromatids B. centromeres C. kinetochores D. centrosomes E. centrioles

A-16 B-16 C-16 D02 E-4

Which of the following methods is not used by cells to regulate the amount of a protein in the cell?

Nuclear pore complexes can regulate the speed at which newly synthesized proteins are exported from the nucleus into the cytoplasm.

know how to label all of the following

A. DNA polymerase B. single-strand binding protein C. Okazaki fragment D. primase E. sliding clamp F. RNA primer G. DNA helicase

Which of the following statements is true? (a) Because endocrine signals are broadcast throughout the body, all cells will respond to the hormonal signal. (b) The regulation of inflammatory responses at the site of an infection is an example of paracrine signaling. (c) Paracrine signaling involves the secretion of signals into the bloodstream for distribution throughout the organism. (d) The axons of neurons typically signal target cells using membrane-bound signaling molecules that act on receptors in the target cells.

Which of the following statements about differentiated cells is true?

Some of the proteins found in differentiated cells are found in all cells of a multicellular organism.

Which of the following is true in reference to G protein signaling? • a. Hormone binding induces an interaction of the receptor with the G protein, stimulating the release of GDP and the exchange of GTP on the α subunit. • b. Once activated, the GTP-bound α subunit dissociates from β/γ and interacts with its target. • c. Activity of the α subunit is terminated by the hydrolysis of GTP to GDP. • d. All of the above

ALL OF THE ABOVE

cyclic AMP (cAMP) is formed from ____ by a crystallization reaction that removes two phosphate groups from ____ and joins the "free" end of the remaining phosphate group to the sugar part of the AMP molecule. The degradation reaction breaks this new bond, forming AMP. _____ continuously converts cAMP to AMP.

ATP ATP cyclic AMP phosphodieterase

cyclic AMP is formed from ---------by the cyclization reaction removes two phosphate groups from -------and joins free end of the remaining phosphate group to the sugar part of the AMP molecule. the degradation reaction breaks this new bond, forming AMP.----------continuously converts cAMP to AMP

ATP ATP cyclic amp phosphodiester

The interior of the trans Golgi network is [acidic/alkaline].

Acidic

Which of the following statements about the cytoskeleton is true?

Actin filaments and microtubules have an inherent polarity, with a plus end that grows more quickly than the minus end.

Plasma membrane proteins are inserted into the membrane in the __________________. The address information for protein sorting in a eukaryotic cell is contained in the __________________ of the proteins.

Amino acid sequence, folded

In cells, dynamic instability typically occurs

At (+) ends only.

Combinatorial control of gene expression __________________________. A) involves only the use of gene activators used together to regulate genes appropriately B) involves groups of transcriptional regulators working together to determine the expression of a gene

Cytoskeleton is particularly important in ____________ cells. A) plant B) animal

Which of the following statements about differentiated cells is true? A) Cells of distinct types express nonoverlapping sets of transcription factors. B) Once a cell has differentiated, it can no longer change its gene expression. C) Once a cell has differentiated, it will no longer need to transcribe RNA. D) Some of the proteins found in differentiated cells are found in all cells of a multicellular organism.

During transcription in __________________ cells, transcriptional regulators that bind to DNA thousands of nucleotides away from a gene's promoter can affect a gene's transcription. A) procaryotic B) eucaryotic

In eucaryotes, but NOT in procaryotes, ribosomes find the start site of translation by ____________________________. A) binding directly to a ribosome-binding site preceding the initiation codon B) scanning along the mRNA from the 5′ end C) recognizing an AUG codon as the start of translation D) binding an initiator tRNA

In principle, _____________ different cell types can an organism having three different types of transcription regulator and thousands of genes create? A) up to 4 B) up to 8

Many bacterial promoters contain a region known as an __________________, to which a specific transcription regulator binds. A) operon B) operator

RNA in cells differs from DNA in that ___________________. A) it is single-stranded and cannot form base pairs B) it is single-stranded and can fold up into a variety of structures

The _________ subunit of a ribosome is the first to interact with new mRNAs. A) large B) small

The human genome encodes about 24,000 genes. The typical differentiated human cell expresses _________________ at any one time? A) between 21,500 and 24,000—at least 90% of the genes B) between 5000 and 15,000 genes

The segments of primary RNA that are cleaved off by spliceosomes are called _________________. A) exons B) introns

Viagra promotes erections. How? a) Viagra is a guanylyl cyclase inhibitor b) Viagra inhibits cGMP phosphodiesterase c) Viagra inhibits nitric oxide synthase d) Viagra inhibits Akt signaling e) Viagra inhibits heterotrimeric G proteins

Which of the following is a second messenger that stimulates release of calcium ions into the cytoplasm? a) Prostaglandins b) Inositol triphosphate c) Cyclic AMP d) Calmodulin

Which of the following statements about RNA splicing is false? A) Conventional introns are not found in bacterial genes. B) For a gene to function properly, every exon must be removed from the primary transcript and then stitched together in the same fashion on every mRNA molecule produced from the same gene. C) Small RNA molecules in the nucleus perform the splicing reactions necessary for the removal of introns. D) Splicing usually occurs after the 5′ cap has been added to the 5' end of the primary transcript.

Which of the following statements about RNAi is true? A) The RNAi mechanism is found only in plants and animals. B) RNAi is induced by foreign double-stranded RNAs, such as from a virus. C) RISC uses the siRNA duplex to locate complementary foreign RNA molecules. D) siRNAs bind to miRNAs to induce RNAi.

________ is not involved in post-transcriptional control? A) dicer B) mediator

____________ are intermediate filaments? A) Tubulins B) Nuclear lamins

__________________ molecules are important in the splicing of RNA transcripts. A) rRNA B) snRNA

16-43 Match the target of the G protein with the appropriate signaling outcome. adenyly cysclase.... ion channels... phospholipase C... a. cleavage of inositol phospholipids b. increase in cAMP levels c. changes in membrane potential

B C A

18-24 Irradiated mammalian cells usually stop dividing and arrest at a G1 checkpoint. Place the following events in the order in which they occur. A. production of p21 B. DNA damage C. inhibition of cyclin-Cdk complexes D. accumulation and activation of p53

B D A C DNA damage accumulation and activation of p53 production of p21 inhibition of cyclin-Cdk complexes

Because hydrogen bonds hold the two strands of a DNA molecule together, the strands can be separated without breaking any covalent bonds. Every unique DNA molecule "melts" at a different temperature. In this context, Tm (melting temperature) is the point at which two strands separate, or become denatured. Order the DNA sequences listed below according to relative melting temperatures (from lowest Tm to highest Tm). Assume that they all begin as stable double-stranded DNA molecules. A. GGCGCACC B. TATTGTCT C. GACTCCTG D. CTAACTGG

B D C A

Molecules to be packaged into vesicles for transport are selected by ________. (a) clathrin. (b) adaptins. (c) dynamin (d) NAREs.

B (adaptins)

Which of the following statements about transport into mitochondria and chloroplasts is false? (a) The signal sequence on proteins destined for these organelles is recognized by a receptor protein in the outer membrane of these organelles. (b) After a protein moves through the protein translocator in the outer membrane of these organelles, the protein diffuses in the lumen until it encounters a protein translocator in the inner membrane. (c) Proteins that are transported into these organelles are unfolded as they are being transported. (d) Signal peptidase will remove the signal sequence once the protein has been imported into these organelles.

B (after a protein moves through the protein translovator in the outer membrane of these organelles, the protein diffuses in the lumen until it encounters a protein translocator in the inner membrane)

You are working in a biotech company that has discovered a small-molecule drug called H5434. H5434 binds to LDL receptors when they are bound to cholesterol. H5434 binding does not alter the conformation of the LDL receptor's intracellular domain. Interestingly, in vitro experiments demonstrate that addition of H5434 increases the affinity of LDL for cholesterol and prevents cholesterol from dissociating from the LDL receptor even in acidic conditions. Which of the following is a reasonable prediction of what may happen when you add H5434 to cells? (a) Cytosolic cholesterol levels will remain unchanged relative to normal cells. (b) Cytosolic cholesterol levels will decrease relative to normal cells. (c) The LDL receptor will remain on the plasma membrane. (d) The uncoating of vesicles will not occur.

B (cytosolic cholesterol levels will decrease relative to normal cells)

Which of the following statements about the protein quality control system in the ER is false? (a) Chaperone proteins help misfolded proteins fold properly. (b) Proteins that are misfolded are degraded in the ER lumen. (c) Protein complexes are checked for proper assembly before they can exit the ER. (d) A chaperone protein will bind to a misfolded protein to retain it in the ER.

B (proteins that are misfolded are degraded in the ER lumen)

Which of the following statements about the endoplasmic reticulum (ER) is false? (a) The ER is the major site for new membrane synthesis in the cell. (b) Proteins to be delivered to the ER lumen are synthesized on smooth ER. (c) Steroid hormones are synthesized on the smooth ER. (d) The ER membrane is contiguous with the outer nuclear membrane.

B (proteins to be delivered to the ER lumen are synthesized on smooth ER)

The formation of __________________ in the endoplasmic reticulum stabilizes protein structure.

Disulfide bonds

Proteins that are constitutively secreted [aggregate/do not aggregate] in the trans Golgi network.

Do not aggregate

Figure Q15-34 shows the organization of a protein that normally resides in the plasma membrane. The boxes labeled 1 and 2 represent membrane-spanning sequences and the arrow represents a site of action of signal peptidase. Given this diagram, which of the following statements must be true? Figure Q15-34 (a) The N-terminus of this protein is cytoplasmic. (b) The C-terminus of this protein is cytoplasmic. (c) The mature version of this protein will span the membrane twice, with both the N- and C-terminus in the cytoplasm. (d) None of the above.

B (the C-terminus of this protein is cytoplasmic)

Which of the following statements is true? (a) Lysosomes are believed to have originated from the engulfment of bacteria specialized for digestion. (b) The nuclear membrane is thought to have arisen from the plasma membrane invaginating around the DNA. (c) Because bacteria do not have mitochondria, they cannot produce ATP in a membrane-dependent fashion. (d) Chloroplasts and mitochondria share their DNA.

B (the nuclear membrane is thought to have arisen from the plasma membrane invaginating around the DNA)

An individual transport vesicle ________. (a) contains only one type of protein in its lumen. (b) will fuse with only one type of membrane. (c) is endocytic if it is traveling toward the plasma membrane. (d) is enclosed by a membrane with the same lipid and protein composition as the membrane of the donor organelle.

B (will fuse with only one type of membrane)

18-72 Of the following mutations, which are likely to cause cell-cycle arrest? If you predict a cell-cycle arrest, indicate whether the cell will arrest in early G1, late G1, or G2. Explain your answers. A. a mutation in a gene encoding a cell-surface mitogen receptor that makes the receptor active even in the absence of the mitogen B. a mutation that destroyed the kinase activity of S-Cdk C. a mutation that allowed G1-Cdk to be active independently of its phosphorylation status D. a mutation that removed the phosphorylation sites on the Rb protein E. a mutation that inhibited the activity of Rb

B and D will cause cell-cycle arrest

A receptor ligand that does not elicit a biological response but binds to a receptor and blocks other molecules from eliciting responses is called a) ligand antagonist b) ligand agonist c) receptor antagonist d) receptor agonist

All of the following statements about monomeric G proteins are true EXCEPT: (A) They are regulated by GTP-GDP exchange proteins. (B) They are regulated by GTPase activating proteins. (C) They regulate enzymes that synthesize cGMP . (D) They regulate vesicle formation. (E) They regulate vesicle fusion.

Gamma-aminobutyric acid-A (GABA-A) receptors are GABA-gated chloride channels. They are found in the plasma membrane of certain types of neurons. Which of the following is TRUE? a) GABA-A receptors are synthesized by ribosomes in the nucleus. b) GABA is a steroid hormone. c) When GABA-A receptors are being synthesized, their ligand-binding site is inside the lumen of the ER. d) Benzodiazepines reduce chloride flow through the plasma membrane. e) GABA-A receptors have seven transmembrane segments.

Your friend works in a biotechnology company and has discovered a drug that blocks the ability of Ran to exchange GDP for GTP. What is the most likely effect of this drug on nuclear transport? (a) Nuclear transport receptors would be unable to bind cargo. (b) Nuclear transport receptors would be unable to enter the nucleus. (c) Nuclear transport receptors would be unable to release their cargo in the nucleus. (d) Nuclear transport receptors would interact irreversibly with the nuclear pore fibrils.

C (nuclear transport receptors would be unable to release their cargo in the nucleus)

The MyoD transcriptional regulator is normally found in differentiating muscle cells and participates in the transcription of genes that produce muscle-specific proteins, such as those needed in contractile tissue. Amazingly, expression of MyoD in fibroblasts causes these cells derived from skin connective tissue to produce proteins normally only seen in muscles. However, some other cell types do not transcribe muscle-specific genes when MyoD is expressed in them. Which of the following statements below is the best explanation of why MyoD can cause fibroblasts to express muscle-specific genes? A) Unlike some other cell types, fibroblasts have not lost the muscle-specific genes from their genome. B) The muscle-specific genes must be in heterochromatin in fibroblasts. C) During their developmental history, fibroblasts have accumulated some transcriptional regulators in common with differentiating muscle cells. D) The presence of MyoD is sufficient to activate the transcription of muscle-specific genes in all cell types.

The following happens when a G-protein-coupled receptor activates a G protein. (a) The β subunit exchanges its bound GDP for GTP. (b) The GDP bound to the α subunit is phosphorylated to form bound GTP. (c) The α subunit exchanges its bound GDP for GTP. (d) It activates the α subunit and inactivates the βγ complex.

The growth factor Superchick stimulates the proliferation of cultured chicken cells. The receptor that binds Superchick is a receptor tyrosine kinase (RTK), and many chicken tumor cell lines have mutations in the gene that encodes this receptor. Which of the following types of mutation would be expected to promote uncontrolled cell proliferation? (a) a mutation that prevents dimerization of the receptor (b) a mutation that destroys the kinase activity of the receptor (c) a mutation that inactivates the protein tyrosine phosphatase that normally removes the phosphates from tyrosines on the activated receptor (d) a mutation that prevents the binding of the normal extracellular signal to the receptor

The lab you work in has discovered a previously unidentified extracellular signal molecule called QGF, a 75,000-dalton protein. You add purified QGF to different types of cells to determine its effect on these cells. When you add QGF to heart muscle cells, you observe an increase in cell contraction. When you add it to fibroblasts, they undergo cell division. When you add it to nerve cells, they die. When you add it to glial cells, you do not see any effect on cell division or survival. Given these observations, which of the following statements is most likely to be true? (a) Because it acts on so many diverse cell types, QGF probably diffuses across the plasma membrane into the cytoplasm of these cells. (b) Glial cells do not have a receptor for QGF. (c) QGF activates different intracellular signaling pathways in heart muscle cells, fibroblasts, and nerve cells to produce the different responses observed. (d) Heart muscle cells, fibroblasts, and nerve cells must all have the same receptor for QGF.

Which of the following is not a protein? a) adenylate cyclase b) PKA c) cAMP d) IP3 receptor e) PLC

Which of the following statements about riboswitches is false? A) Riboswitches can block the production of mRNAs. B) Riboswitches can control the translation of mRNAs. C) Riboswitches are made from rRNAs. D) Riboswitches can bind metabolites.

Which of the following statements about the cytoskeleton is false? A) The cytoskeleton is made up of three types of protein filament. B) The cytoskeleton is important for cell division and DNA segregation. C) Protein monomers that are held together with covalent bonds form cytoskeletal filaments. D) The cytoskeleton of a cell can change in response to the environment.

Which of the following statements is true? a) Calcium and diacylglycerol in combination activate adenylate cyclase. b) Many enzyme-coupled receptors (such as receptor tyrosine kinases) have intracellular protein domains that interact with heterotrimeric G-proteins. c) In all eukaryotic cells, transport vesicles continually bud from the trans golgi network and fuse with the plasma membrane, a process called 'constitutive exocytosis'. d) Ribosomes in the cytosol are directed to the ER because the protein they are making has an ER signal sequence, which is recognized by a signal recognition particle inside the lumen of the ER. e) All of the statements above are true.

Proteins enter the nucleus in their __________________ form.

Sorting signal

Which of the following statements is true? a) Large hydrophilic extracellular signal molecules such as steroid hormones and nitric oxide cannot diffuse directly across the plasma membrane. Thus, they bind to intracellular receptors, which usually act as transcription regulators or enzymes when activated. b) There are three main classes of cell-surface receptors: 1) adenylate cyclase, 2) phospholipase C, and 3) nitic oxide synthase. c) GPCRs activate a class of trimeric GTP-binding proteins called G proteins; these act as molecular switches, transmitting the signal onward for a short period and then switching themselves off by hydrolyzing GTP to GDP. d) IP3 opens calcium channels in the membrane of the endoplasmic reticulum, allowing calcium ions to flow from the cytosol into the ER. e) Protein kinase A is responsible for the synthesis of cAMP.

Which of the following statements is true? A) Ribosomes are large RNA structures composed solely of rRNA. B) A ribosome binds three tRNA at a time. C) rRNA contains the catalytic activity that joins amino acids together. D) A ribosome binds only one tRNA at any given time.

Your friend is studying mouse fur color and has isolated the GPCR responsible for determining its color, as well as the extracellular signal that activates the receptor. She finds that, on addition of the signal to pigment cells (cells that produce the pigment determining fur color), cAMP levels rise in the cell. She starts a biotech company, and the company isolates more components of the signaling pathway responsible for fur color. Using transgenic mouse technology, the company genetically engineers mice that are defective in various proteins involved in determining fur color. The company obtains the following results. Normal mice have beige (very light brown) fur color. Mice lacking the extracellular signal have white fur. Mice lacking the GPCR have white fur. Mice lacking cAMP phosphodiesterase have dark brown fur. Your friend has also made mice that are defective in the α subunit of the G protein in this signaling pathway. The defective α subunit works normally except that, once it binds GTP, it cannot hydrolyze GTP to GDP. What color do you predict that the fur of these mice will be? a) very light brown b) white c) dark brown d) black

Which of the following statements about the unfolded protein response (UPR) is false? (a) Activation of the UPR results in the production of more ER membrane. (b) Activation of the UPR results in the production of more chaperone proteins. (c) Activation of the UPR occurs when receptors in the cytoplasm sense misfolded proteins. (d) Activation of the UPR results in the cytoplasmic activation of gene regulatory proteins.

C (activation of the UPR occurs when receptors in the cytoplasm sense misfolded proteins)

Most proteins destined to enter the endoplasmic reticulum _________. (a) are transported across the membrane after their synthesis is complete. (b) are synthesized on free ribosomes in the cytosol. (c) begin to cross the membrane while still being synthesized. (d) remain within the endoplasmic reticulum.

C (begin to cross the membrane while still being synthesized)

Which of the following statements is true? (a) The signal sequences on mitochondrial proteins are usually at the C-terminus. (b) Most mitochondrial proteins are not imported from the cytosol but are synthesized inside the mitochondria. (c) Chaperone proteins in the mitochondria facilitate the movement of proteins across the outer and inner mitochondrial membranes. (d) Mitochondrial proteins cross the membrane in their native, folded state.

C (chaperone proteins in the mitochondria facilitate the movement of proteins across the outer and inner mitochondrial membranes)

Vesicles from the ER enter the Golgi at the ______. (a) medial cisternae. (b) trans Golgi network. (c) cis Golgi network. (d) trans cisternae.

C (cis Golgi network)

Your friend has just joined a lab that studies vesicle budding from the Golgi and has been given a cell line that does not form mature vesicles. He wants to start designing some experiments but wasn't listening carefully when he was told about the molecular defect of this cell line. He's too embarrassed to ask and comes to you for help. He does recall that this cell line forms coated pits but vesicle budding and the removal of coat proteins don't happen. Which of the following proteins might be lacking in this cell line? (a) clathrin (b) Rab (c) dynamin (d) adaptin

C (dynamin)

Signal sequences that direct proteins to the correct compartment are _________. (a) added to proteins through post-translational modification. (b) added to a protein by a protein translocator. (c) encoded in the amino acid sequence and sufficient for targeting a protein to its correct destination. (d) always removed once a protein is at the correct destination.

C (encoded in the amino acid sequence and sufficient for targeting a protein to its correct destination)

In which cellular location would you expect to find ribosomes translating mRNAs that encode ribosomal proteins? (a) the nucleus (b) on the rough ER (c) in the cytosol (d) in the lumen of the ER

C (in the cytosol)

Which of the following organelles is not part of the endomembrane system? (a) Golgi apparatus (b) the nucleus (c) mitochondria (d) lysosomes

C (mitochondria)

Which of the following statements about nuclear transport is true? (a) mRNAs and proteins transit the nucleus through different types of nuclear pores. (b) Nuclear import receptors bind to proteins in the cytosol and bring the proteins to the nuclear pores, where the proteins are released from the receptors into the pores for transit into the nucleus. (c) Nuclear pores have water-filled passages that small, water-soluble molecules can pass through in a nonselective fashion. (d) Nuclear pores are made up of many copies of a single protein.

C (nuclear pores have water-filled passages that small, water-soluble molecules can pass through in a nonselective fashion)

Which of the following statements is true? (a) Proteins destined for the ER are translated by a special pool of ribosomes whose subunits are always associated with the outer ER membrane. (b) Proteins destined for the ER translocate their associated mRNAs into the ER lumen where they are translated. (c) Proteins destined for the ER are translated by cytosolic ribosomes and are targeted to the ER when a signal sequence emerges during translation. (d) Proteins destined for the ER are translated by a pool of cytosolic ribosomes that contain ER-targeting sequences that interact with ER-associated protein translocators.

C (proteins destined for the ER are translated by cytosolic ribosomes and are targeted to the ER when a signal sequence emerges during translation)

Which of the following statements about vesicular membrane fusion is false? (a) Membrane fusion does not always immediately follow vesicle docking. (b) The hydrophilic surfaces of membranes have water molecules associated with them that must be displaced before vesicle fusion can occur. (c) The GTP hydrolysis of the Rab proteins provides the energy for membrane fusion. (d) The interactions of the v-SNAREs and the t-SNAREs pull the vesicle membrane and the target organelle membrane together so that their lipids can intermix.

C (the GTP hydrolysis of the Rab proteins provides the energy for membrane fusion)

Cells have oligosaccharides displayed on their cell surface that are important for cell-cell recognition. Your friend discovered a transmembrane glycoprotein, GP1, on a pathogenic yeast cell that is recognized by human immune cells. He decides to purify large amounts of GP1 by expressing it in bacteria. To his purified protein he then adds a branched 14-sugar oligosaccharide to the asparagine of the only Asn-X-Ser sequence found on GP1 (Figure Q15-48). Unfortunately, immune cells do not seem to recognize this synthesized glycoprotein. Which of the following statements is a likely explanation for this problem? Figure Q15-48 (a) The oligosaccharide should have been added to the serine instead of the asparagine. (b) The oligosaccharide should have been added one sugar at a time. (c) The oligosaccharide needs to be further modified before it is mature. (d) The oligosaccharide needs a disulfide bond.

C (the oligosaccharide need to be further modified before it is mature)

Figure Q15-57 shows the orientation of the Krt1 protein on the membrane of a Golgi-derived vesicle that will fuse with the plasma membrane. Figure Q15-57 Given this diagram, which of the following statements is true? (a) When this vesicle fuses with the plasma membrane, the entire Krt1 protein will be secreted into the extracellular space. (b) When this vesicle fuses with the plasma membrane, the C-terminus of Krt1 will be inserted into the plasma membrane. (c) When this vesicle fuses with the plasma membrane, the N-terminus of Krt1 will be in the extracellular space. (d) When this vesicle fuses with the plasma membrane, the N-terminus of Krt1 will be cytoplasmic.

C (when this vesicle fuses with the plasma membrane, the N-terminus of Krt1 will be in the extracellular space)

The following Figure shows the leading edge of a lamellipodium. Which of the following statements is false?

Capping proteins bind to the minus end of actin filaments.

New plasma membrane proteins reach the plasma membrane by the [regulated/constitutive] exocytosis pathway.

Constitutive

New plasma membrane reaches the plasma membrane by the [regulated/constitutive] exocytosis pathway.

Constitutive

Which of the following statements about the cytoskeleton is false?

Covalent bonds between protein monomers hold together cytoskeletal filaments.

"Androgel" is testosterone dissolved in a gel. It is rubbed onto the skin as 'testosterone replacement therapy' to treat low testosterone, most often in males. Which of the following is TRUE? a) Testosterone cannot penetrate membranes, and therefore is unlikely to penetrate the skin. b) Testosterone binds to G-protein coupled receptors. c) Androgel is a testosterone receptor antagonist. d) Testosterone receptor antagonists would block the effect of Androgel. e) Androgel is a receptor in the cytoplasm, which travels to the nucleus when testosterone binds.

Three phospholipids X, Y, and Z are distributed in the plasma membrane as indicated in the Figure. For which of these phospholipids does a flippase probably exist?

Y and Z

Naloxone is a drug given to individuals who present in the emergency room suspected of opiate overdose (such as heroin). Naloxone acts on opiate receptors to block the binding of the opiates in the body, thus negating their toxic effects. The drug acts quite quickly such that patients will suddenly wake up from unconsciousness upon administration. Naloxone has a half-life of around 30 minutes (as compared with 4 hours for many opiates). As such, the patient may revert into the unconscious state when the naloxone effects have worn off and the opiates continue to have their effects. Which of the following types of inhibition is POSSIBLE of the naloxone-opiate receptor system? I. Noncompetitive inhibitor II. Competitive inhibitor III. Nonreversible Inhibitor a) I only b) II only c) II and III only d) I, II, and III

The length of time a G protein will signal is determined by _______. (a) the activity of phosphatases that turn off G proteins by dephosphorylating Gα. (b) the activity of phosphatases that turn GTP into GDP. (c) the degradation of the G protein after Gαseparates from Gβγ (d) the GTPase activity of Gα

Which of the following canonical signaling cascades is NOT correctly described? a) Phospholipase C (PLC) cleaves PIP2 into IP3 and DAG; DAG then activates protein kinase C. b) RAS activates RAF, which phosphorylates a MAP kinase kinase, which phosphorylates a MAP kinase, which phosphorylates a transcription factor. c) IP3 triggers opening of IP3 receptors in the endoplasmic reticulum, allowing calcium to move from the ER to the cytoplasm. d) A GTPase-activating protein (GAP) turns on RAS by triggering release of GDP and binding of GTP. e) Mechanical pressure on the extracellular portion of a mechanoreceptor causes opening of an ion channel portion of the receptor, allowing calcium into the cytoplasm.

Which of the following is the most accurate description of intercellular (cell to cell) chemical signaling? a) A signal molecule binds to a receptor in the plasma membrane, triggering activation of G-proteins that activate other proteins by phosphorylation. These phosphorylated proteins cause a cellular response b) A signal molecule binds to a receptor, which is by definition any sort of protein that binds the signal molecule. After this receptor binds the signaling molecule (also called a 'ligand'), the receptor converts to an adenylate cyclase and generates CaM kinase, which phsophorylates other proteins, eventually leading to a cellular response c) A signal molecule, typically named Bob, wanders down the street until it bumps into a lamppost and falls over. Somewhere, a dog howls. d) A signal molecule binds to a receptor, which can be inside the cell or embedded in the plasma membrane, causing activation of this receptor. Receptor activation then triggers a 'signaling cascade', in which a series of enzymes (such as CaM kinase, protein kinase, and adenylate cyclase) catalyze the formation of other signaling molecules that eventually activate a cellular response. e) Signaling molecules can be released from nearby cells ('endocrine signaling'), transported from cells far away (paracrine signaling), or the target cell itself ('autocrine signaling'). In each case, the signaling molecule binds to receptors on or in the target cell to cause either a change in intracellular ion concentration (i.e. an increase in intracellular calcium) or activation of intracellular G-proteins or enzymes like kinases. G-proteins and kinases in turn activate other proteins and/or generate 'second messengers', which eventually leads to a cellular response

Which of the following methods is not used by cells to regulate the amount of a protein in the cell? A) Genes can be transcribed into mRNA with different efficiencies. B) Many ribosomes can bind to a single mRNA molecule. C) Proteins can be tagged with ubiquitin, marking them for degradation. D) Nuclear pore complexes can regulate the speed at which newly synthesized proteins are exported from the nucleus into the cytoplasm.

Which of the following statements about DNA methylation in eucaryotes is false? A) Appropriate inheritance of DNA methylation patterns involves maintenance methyltransferase. B) DNA methylation involves a covalent modification of cytosine bases. C) Methylation of DNA attracts proteins that block gene expression. D) Immediately after DNA replication, each daughter helix contains one methylated DNA strand, which corresponds to the newly synthesized strand.

Which of the following statements about G-protein-coupled receptors (GPCRs) is false? (a) GPCRs are the largest family of cell-surface receptors in humans. (b) GPCRs are used in endocrine, paracrine, and neuronal signaling. (c) GPCRs are found in yeast, mice, and humans. (d) The different classes of GPCR ligands (proteins, amino acid derivatives, or fatty acids) bind to receptors with different numbers of transmembrane domains.

Which of the following statements about the cytoskeleton is true? A) All actin, microtubules, and intermediate filaments are present in the cytoplasm. B) The cytoskeleton provides a rigid and unchangeable structure important for the shape of the cell. C) The three cytoskeletal filaments perform distinct tasks in the cell and act completely independently of one another. D) Actin filaments and microtubules have an inherent polarity, with a plus end that grows more quickly than the minus end.

Which of the following statements is false? (a) Nucleotides and amino acids can act as extracellular signal molecules. (b) Some signal molecules can bind directly to intracellular proteins that bind DNA and regulate gene transcription. (c) Some signal molecules are transmembrane proteins. (d) Dissolved gases such as nitric oxide (NO) can act as signal molecules, but because they cannot interact with proteins they must act by affecting membrane lipids.

Which of the following choices reflects the appropriate order of locations through which a protein destined for the plasma membrane travels? (a) lysosome à endosome à plasma membrane (b) ER à lysosome à plasma membrane (c) Golgi à lysosome à plasma membrane (d) ER à Golgi à plasma membrane

D (ER, golgi, plasma membrane)

Which of the following protein families are not involved in directing transport vesicles to the target membrane? (a) SNAREs (b) Rabs (c) tethering proteins (d) adaptins

D (adaptins)

After isolating the rough endoplasmic reticulum from the rest of the cytoplasm, you purify the RNAs attached to it. Which of the following proteins do you expect the RNA from the rough endoplasmic reticulum to encode? (a) soluble secreted proteins (b) ER membrane proteins (c) plasma membrane proteins (d) all of the above

D (all of the above)

Which of the following statements about disulfide bond formation is false? (a) Disulfide bonds do not form under reducing environments. (b) Disulfide bonding occurs by the oxidation of pairs of cysteine side chains on the protein. (c) Disulfide bonding stabilizes the structure of proteins. (d) Disulfide bonds form spontaneously within the ER because the lumen of the ER is oxidizing.

D (disulfide bonds form spontaneously within the ER because the lumen of the ER is oxidizing)

Where are proteins in the chloroplast synthesized? (a) in the cytosol (b) in the chloroplast (c) on the endoplasmic reticulum (d) in both the cytosol and the chloroplast

D (in both the cytosol and the chloroplast)

Different glycoproteins can have a diverse array of oligosaccharides. Which of the statements below about this diversity is true? (a) Extensive modification of oligosaccharides occurs in the extracellular space. (b) Different oligosaccharides are covalently linked to proteins in the ER and the Golgi. (c) A diversity of oligosaccharyl transferases recognizes specific protein sequences, resulting in the linkage of a variety of oligosaccharides to proteins. (d) Oligosaccharide diversity comes from modifications that occur in the ER and the Golgi of the 14-sugar oligosaccharide added to the protein in the ER.

D (oligosaccharide diversity comes from modifications that occur in the ER and the Golgi of the 14-sugar oligosaccharide added to the protein in the ER)

You are interested in Fuzzy, a soluble protein that functions within the ER lumen. Given that information, which of the following statements must be true? (a) Fuzzy has a C-terminal signal sequence that binds to SRP. (b) Only one ribosome can be bound to the mRNA encoding Fuzzy during translation. (c) Fuzzy must contain a hydrophobic stop-transfer sequence. (d) Once the signal sequence from Fuzzy has been cleaved, the signal peptide will be ejected into the ER membrane and degraded.

D (once the signal sequence from Fuzzy has been cleaved, the signal peptide will be ejected into the ER membrane and degraded)

Which of the following statements about a protein in the lumen of the ER is false? (a) A protein in the lumen of the ER is synthesized by ribosomes on the ER membrane. (b) Some of the proteins in the lumen of the ER can end up in the extracellular space. (c) Some of the proteins in the lumen of the ER can end up in the lumen of an organelle in the endomembrane system. (d) Some of the proteins in the lumen of the ER can end up in the plasma membrane.

D (plasma membrane proteins come from proteins in the ER membrane, not from the ER lumen)

N-linked oligosaccharides on secreted glycoproteins are attached to ________. (a) nitrogen atoms in the polypeptide backbone. (b) the serine or threonine in the sequence Asn-X-Ser/Thr. (c) the N-terminus of the protein. (d) the asparagine in the sequence Asn-X-Ser/Thr.

D (the asparagine in the sequence Asn-X-Ser/Thr)

Proteins that are fully translated in the cytosol do not end up in _______. (a) the cytosol. (b) the mitochondria. (c) the interior of the nucleus. (d) transport vesicles.

D (transport vesicles)

Which of the following statements is false?

Dissolved gases such as nitric oxide (NO) can act as signal molecules, but because they cannot interact with proteins they must act by affecting membrane lipids.

During their developmental history, fibroblasts have accumulated some transcriptional regulators in common with differentiating muscle cells.

Assuming memory formation requires activation of the PKA pathway leading to CREB phosphorylation, which of the following pills might make you smart? a) An adenylyl cyclase antagonist b) A MAP Kinase antagonist c) A Guanylyl cyclase agonist d) An inhibitor of Ras e) A phosphodiesterase inhibitor

The KDEL sequence, found on luminal proteins of the ER, is responsible for (A) translocation of proteins into the ER lumen (B) insertion of proteins into the membrane of the ER (C) quality control in the ER (D) recognition by signal peptidase of the signal sequence (E) retrieval of ER luminal proteins from the Golgi

Fluids and macromolecules are transported into the cell via the __________________ pathway.

Endocytic

Transport vesicles link organelles of the __________________ system.

Endomembrane

Plasma membrane proteins are inserted into the membrane in the __________________.

Endoplasmic reticulum

Which of the following statements is true?

Extracellular signal molecules that are hydrophilic must bind to a cell-surface receptor so as to signal a target cell to change its behavior.

what is the death receptor?

Fas receptor

Which of the following statements about RNA splicing is false?

For a gene to function properly, every exon must be removed from the primary transcript and then stitched together in the same fashion on every mRNA molecule produced from the same gene.

one important system invovles hormones that stimulate a membrane bound ------which the stimulates adenylate to produce cAMP (in this case cAMP is a second messenger

G-protein

GPCRS stands for

G-protein coupled receptors

15-37 For each of the following sentences, fill in the blanks with the best word or phrase selected from the list below. Not all words or phrases will be used; use each word or phrase only once. Proteins are transported out of a cell via the *secretory* or *exocytic* pathway. Fluids and macromolecules are transported into the cell via the *endocytic* pathway All proteins being transported out of the cell pass through the *endoplasmic reticulum* and the __________________. carbohydrate Golgi apparatus disulfide bonds hydrogen bonds endocytic ionic bonds endomembrane lysosome endoplasmic reticulum protein endosome secretory exocytic

Golgi apparatus.

diversity among the oligosaccharide chains found in the carbohydrate coating of the cell surface can be achieved in which of the following ways

all of the above (varying the types of sugar monomers used/types of linkages between sugars/the number of branches in the chain)

18-1 Growth occurs in __________________, __________________, and __________________ phases of the cell cycle. A cell does not enter mitosis until it has completed __________________ synthesis.

G1 S G2 DNA

18-31 Cells can pause in G1 when DNA is damaged, and can pause in S when there are replication errors. Indicate whether the mechanism below applies to a G1 arrest, an S-phase arrest, both types of arrest, or neither. A. p53 activates the transcription of a Cdk inhibitor. B. Cyclins are phosphorylated and destroyed. C. Cdk is unable to phosphorylate its substrates. D. The Cdc25 phosphatase is inhibited.

G1 arrest neither both S-phase arrest

about one third of all drugs used today work through -----

GPCRs

16-19 __________________ proteins can act as molecular switches, letting a cell know that a signal has been received. Enzymes that phosphorylate proteins, termed ___________, can also serve as molecular switches; the actions of these enzymes are countered by the activity of __________________

GTP-binding; protein kinases; protein phosphatatses

16-27 The intrinsic __________________ activity of the α subunit is important for inactivating the G protein. __________________ inhibits this activity of the α subunit, thereby keeping the subunit in an active state.

GTPase; cholera toxin

When the neurotransmitter acetylcholine is applied to skeletal muscle cells, it binds the acetylcholine receptor and causes the muscle cells to contract. Succinylcholine, which is a chemical analog of acetylcholine, binds to the acetylcholine receptor on skeletal muscle cells but causes the muscle cells to relax; it is therefore often used by surgeons as a muscle relaxant. Propose a model for why succinylcholine causes muscle relaxation. What might be the mechanism to explain the different activities of acetylcholine and succinylcholine on the acetylcholine receptor?

Given that Succinylcholine is a chemical analog of acetylcholine (Ach), they likely have very similar structures. This is supported by the fact that both molecules bind to the same (Ach) receptor. The most likely explanation is that Ach binding to its receptor produces a cascade (or other response) that results in muscle cell contraction while Succinylcholine binding to the same receptor interferes with Ach binding; further, Succinylcholine binding to the receptor does not induce a receptor shape-change that results in intracellular signaling. This blocking of Ach-induced contraction results in muscle cell relaxation (i.e., the absence of contraction—no signal to contract). Simply put, Succinylcholine is a competitive inhibitor of Ach binding.

15-5 For each of the following sentences, fill in the blanks with the best word or phrase selected from the list below. Not all words or phrases will be used; use each word or phrase only once. The *cytosol*makes up about half of the total cell volume of a typical eukaryotic cell. Ingested materials within the cell will pass through a series of compartments called *endosomes* on their way to the *lysosome*_, which contains digestive enzymes and will ultimately degrade the particles and macromolecules taken into the cell and will also degrade worn-out organelles.The __________________ has a cis and trans face cytosol Golgi apparatus nucleus endoplasmic reticulum lysosome peroxisomes endosomes mitochondria plasma membrane

Golgi apparatus

The __________________ has a cis and trans face and receives proteins and lipids from the __________________, a system of interconnected sacs and tubes of membranes that typically extends throughout the cell.

Golgi apparatus, endoplasmic reticulum

. ___________________________ allows the flawless repair of DNA double-strand breaks.

Homologous recombination

The amino acid sequences below represent the sequences of transmembrane helices. The characteristics (hydrophobic, amphipathic etc.)of α helices that form a channel that contains a pore are different from those that form a single transmembrane domain. Select the helix that forms a single transmembrane domain.

IMIVLVMLLNIGLAILFVHF

Which of the following statements about DNA methylation in eucaryotes is false?

Immediately after DNA replication, each daughter helix contains one methylated DNA strand, which corresponds to the newly synthesized strand.

Which of the following is not a commonly observed consequence of the binding of a signaling molecule to its cell surface receptor? • a. Receptor dimerization • b. Receptor phosphorylation • c. Conformational changes in the receptor • d. Increased synthesis of the receptor

Increased synthesis of the receptor

What type of activity would a cytosolic receptor be expected to have if it typically elicits a very rapid cellular response after binding to its chemical signaling molecule?

It is likely that the cytosolic receptor has some sort of enzymatic activity (like the guanalyl cyclase activity described in class for NO) because a rapid response would be elicited when the receptor were bound by a signaling molecule that could pass through the membrane. Upon the signal molecule's binding to the cytosolic receptor, the receptor would change shape and alter its activity (either up or down) to alter cellular behavior rapidly.

You have discovered an "Exo-" mutant form of DNA polymerase in which the 3′-to-5′ exonuclease function has been destroyed but the ability to join nucleotides together is unchanged. Which of the following properties do you expect the mutant polymerase to have?

It will be more likely to generate mismatched base pairs.

18-32 The cell cycle consists of an alternation between __________________, which appears as a period of dramatic activity under the microscope, and a preparative period called __________________, which consists of three phases called __________________, __________________, and __________________.

M phase interphase G1 phase S phase G2 phase

16-53 Some intracellular signaling pathways involve chains of protein kinases that phosphorylate each other, as seen in the __________________ signaling module. Lipids can also relay signals in the cell, as we observe when phospholipase C cleaves the sugar-phosphate head off a lipid molecule to generate the two small messenger molecules __________________ (which remains embedded in the plasma membrane) and __________________ (which diffuses into the cytosol)

MAP kinase; diacylglycerol; IP3

Which of the following statements about the ubiquitin-proteasome pathway is false?

Misfolded proteins are delivered to the proteasome, where they are sequestered from the cytoplasm and can attempt to refold.

16-53 Cells signal to one another in various ways. Some use extracellular signal molecules that are dissolved gases, such as __________________, which can diffuse easily into cells. Others use cytokines, which bind to cytokine receptors. Cytokine receptors have no intrinsic enzyme activity but are associated with cytoplasmic tyrosine kinases called __________________s, which become activated on the binding of cytokine to its receptor and go on to phosphorylate and activate cytoplasmic transcriptional regulators called __________________s

NO; JAK STAT;

During the chain elongation process of translating an mRNA into protein, the growing polypeptide chain attached to a tRNA is bound to the __________________-site of the ribosome.

activated --------can also phosphorylate aNd thereby regulate other proteins and enzymes in the cystosol

PKA

cyclic AMP exerts its effects in animal cells mainly by activating the enzyme ____ which catalyzes the transfer of the terminal phosphate group from ATP to specific serines or threonines of selected proteins

PKA

the increase in cyclic AMP activates ________, which phosphorylates and activates an enzyme called phosphorylase kinase

PKA

the enzyme activated by diacylglycerol is called ------becasue it is Ca+ dependent

PKC

The sequences for two different tripeptides are written out below. Indicate whether you expect to find them in the inner core or on the surface of a cytosolic protein: A.Serine-Threonine-Tyrosine B.Alanine-Glycine-Leucine

Peptide B is in the inner core, while Peptide A would be on the outer surface.

Eukaryotic cells are continually taking up materials from the extracellular space by the process of endocytosis. One type of endocytosis is __________________, which uses __________________ proteins to form small vesicles containing fluids and molecules.

Pinocytosis, clathrin

Diacylglycerol activates which of the following enzymes? - A. Protein kinase A - B. Protein kinase C - C. MAP kinase - D. Tyrosine kinase - E. Phosphorylase b kinase

Protein kinase C

Which of the following statements about the cytoskeleton is false?

Protein monomers that are held together with covalent bonds form cytoskeletal filaments.

Macrophages are especially suited for this process, as they extend __________________ (sheetlike projections of their plasma membrane) to surround the invading microorganisms.

Pseudopods

QGF activates different intracellular signaling pathways in heart muscle cells, fibroblasts, and nerve cells to produce the different responses observed

18-50 Which of the following statements about kinetochores is true? (a) Kinetochores assemble onto chromosomes during late prophase. (b) Kinetochores contain DNA-binding proteins that recognize sequences at the telomere of the chromosome. (c) Kinetochore proteins bind to the tubulin molecules at the minus end of microtubules. (d) Kinetochores assemble on chromosomes that lack centromeres.

a (kinetochores assemble onto chromosomes during late prophase)

transcription in bacteria differs from transcription in a eukaryotic cell because

RNA polymerase (along with its sigma subunit) can initiate transcription on its own

Which of the following statements about RNAi is true?

RNAi is induced by foreign double-stranded RNAs, such as from a virus.

Insulin is secreted from pancreatic cells by the [regulated/constitutive] exocytosis pathway.

Regulated

Cell movement involves the coordination of many events in the cell. Which of the following phenomena are not required for cell motility?

Release of Ca2+ from the sarcoplasmic reticulum.

Which of the following statements about riboswitches is false?

Riboswitches are made from rRNAs.

18-1 The four phases of the cell cycle, in order, are G1, __________________, __________________, and __________________. A

S G2 M

18-1 A cell contains the most DNA after __________________ phase of the cell cycle. A cell is smallest in size after __________________ phase of the cell cycle

S M

Proteins are transported out of a cell via the __________________ or __________________ pathway.

Secretory, exocytic

Sometimes, chemical damage to DNA can occur just before DNA replication begins, not giving the repair system enough time to correct the error before the DNA is duplicated. This gives rise to mutation. If the adenosine in the sequence TCAT is depurinated and not repaired, which of the following is the point mutation you would observe after this segment has undergone two rounds of DNA replication?

TCT

You have a bacterial strain with a mutation that removes the transcription termination signal from the Abd gene. Which of the following statements describes the most likely effect of this mutation on Abd transcription?

The Abd RNA from the mutant strain will be longer than normal.

Which of the following statements about the Lac operon is false?

The Lac repressor binds when lactose is present in the cell.

What would be the most obvious outcome of repeated cell cycles consisting of S phase and M phase only?

The cells produced would get smaller and smaller.

Which of the following statements about skeletal muscle contraction is false?

The changes in voltage across the plasma membrane that occur when a muscle cell receives a signal from the nervous system cause an influx of Ca2+ into the sarcoplasmic reticulum, triggering a muscle contraction.

The lab you work in has discovered a previously unidentified extracellular signal molecule called X, a 75,000-dalton protein. You add purified protein X to different types of cells to determine its effect(s). When you add protein X to heart muscle cells, you observe an increase in cell contraction. When you add it to fibroblasts, they undergo cell division. When you add it to nerve cells, they die. When you add it to glial cells, you do not see any effect on cell division or survival. How might these observations be explained?

The differences in response (or lack thereof) are easily explained by the presence/absence of a receptor for protein X, by the TYPE of protein X (different receptors yield different responses), and by the intracellular cascade(s) that occur after receptor binding. (i.e., even with the same receptor, different intracellular cascades can produce different cellular responses).

Proteins that remain in the cytosol do not contain a __________________.

Transport vesicles

Proteins are transported into the Golgi apparatus via __________________. The proteins transported into the endoplasmic reticulum by __________________ are in their __________________ form.

Transport vesicles, protein translocators, unfolded

G proteins and monomeric GTPases are active when GTP is bound and inactive when GDP is bound. T/F?

True

The extent of complementarity of a miRNA with its target mRNA determines ________________.

Whether the mRNA will be degraded by a nuclease within the RISC or transported elsewhere in the cell for degradation.

Rank the following types of cell signaling from 1 to 4, with 1 representing the type of signaling in which the signal molecule travels the least distance before it encounters a responsive cell and 4 the type of signaling in which the signal molecule has the ability to travel the longest distance. ______ paracrine signaling ______ juxtacrine signaling ______ synaptic signaling ______ endocrine signaling

__3___ paracrine signaling __1___ juxtacrine signaling __2___ synaptic signaling __4___ endocrine signaling

18-26 Cells in the G0 state ________________. (a) do not divide. (b) cannot re-enter the cell cycle. (c) have entered this arrest state from either G1 or G2. (d) have duplicated their DNA.

16-40 You are interested in cell-size regulation and discover that signaling through a GPCR called ERC1 is important in controlling cell size in embryonic rat cells. The G protein downstream of ERC1 activates adenylyl cyclase, which ultimately leads to the activation of PKA. You discover that cells that lack ERC1 are 15% smaller than normal cells, while cells that express a mutant, constitutively activated version of PKA are 15% larger than normal cells. Given these results, which of the following treatments to embryonic rat cells should lead to smaller cells? (a) addition of a drug that causes cyclic AMP phosphodiesterase to be hyperactive (b) addition of a drug that prevents GTP hydrolysis by Gα (c) addition of a drug that activates adenylyl cyclase (d) addition of a drug that mimics the ligand of ERC1 a (addition of a drug that causes cycle AMP phosphodiesterase to be hyperactive)

a (addition of a drug that causes cycle AMP phosphodiesterase to be hyperactive)

16-32 Acetylcholine binds to a GPCR on heart muscle, making the heart beat more slowly. The activated receptor stimulates a G protein, which opens a K+ channel in the plasma membrane, as shown in Figure Q16-32. Which of the following would enhance this effect of the acetylcholine? Figure Q16-32 (a) addition of a high concentration of a nonhydrolyzable analog of GTP (b) addition of a drug that prevents the α subunit from exchanging GDP for GTP (c) mutations in the acetylcholine receptor that weaken the interaction between the receptor and acetylcholine (d) mutations in the acetylcholine receptor that weaken the interaction between the receptor and the G protein

a (addition of a high concentration of nonhydrolyzable analog of GTP)

18-57 Which of the following precede the re-formation of the nuclear envelope during M phase in animal cells? (a) assembly of the contractile ring (b) decondensation of chromosomes (c) reassembly of the nuclear lamina (d) transcription of nuclear genes

a (assembly of the contractile ring happens before reformation of nuclear envelope)

18-65 Programmed cell death occurs ________________. (a) by means of an intracellular suicide program. (b) rarely and selectively only during animal development. (c) only in unhealthy or abnormal cells. (d) only during embryonic development.

a (by means of an intracellular suicide program)

18-40 The principal microtubule-organizing center in animal cells is the ____________. (a) centrosome. (b) centromere. (c) kinetochore. (d) cell cortex.

a (centrosome-microtubule organizing center)

16-49 Which of the following mechanisms is not directly involved in inactivating an activated RTK? (a) dephosphorylation by serine/threonine phosphatases (b) dephosphorylation by protein tyrosine phosphatases (c) removal of the RTK from the plasma membrane by endocytosis (d) digestion of the RTK in lysosomes

a (dephosphorylation by serine/threonine phosphatases)

16-22 Which of the following statements is true? (a) Extracellular signal molecules that are hydrophilic must bind to a cellsurface receptor so as to signal a target cell to change its behavior. (b) To function, all extracellular signal molecules must be transported by their receptor across the plasma membrane into the cytosol. (c) A cell-surface receptor capable of binding only one type of signal molecule can mediate only one kind of cell response. (d) Any foreign substance that binds to a receptor for a normal signal molecule will always induce the same response that is produced by that signal molecule on the same cell type.

a (extracellular signal molecules that are hydrophilic must bind to a cellsurface receptor so as to signal a target cell to change its behavior)

18-33 Which of the following does not occur during M phase in animal cells? (a) growth of the cell (b) condensation of chromosomes (c) breakdown of nuclear envelope (d) attachment of chromosomes to microtubules

a (growth of the cell)

18-22 Mitogens are _____. (a) extracellular signals that stimulate cell division. (b) transcription factors important for cyclin production. (c) kinases that cause cells to grow in size. (d) produced by mitotic cells to keep nearby neighboring cells from dividing. a (mitogens are extracellular signals that stimulate cell division)

a (mitogens are extracellular signals that stimulate cell division)

18-8 Which of the following statements about the cell cycle is false? (a) Once a cell decides to enter the cell cycle, the time from start to finish is the same in all eukaryotic cells. (b) An unfavorable environment can cause cells to arrest in G1. (c) A cell has more DNA during G2 than it did in G1. (d) The cleavage divisions that occur in an early embryo have short G1 and G2 phases.

a (once a cell decides to enter the cell cycle, the time from start to finish is the same in all eukaryotic cells)

16-23 Which of the following statements about molecular switches is false? (a) Phosphatases remove the phosphate from GTP on GTP-binding proteins, turning them off. (b) Protein kinases transfer the terminal phosphate from ATP onto a protein. (c) Serine/threonine kinases are the most common types of protein kinase. (d) A GTP-binding protein exchanges its bound GDP for GTP to become activated.

a (phosphatases remove the phosphate from GTP on GTP-binding proteins, turning them off)

18-61 Cytokinesis in animal cells ________________. (a) requires ATP. (b) leaves a small circular "scar" of actin filaments on the inner surface of the plasma membrane. (c) is often followed by phosphorylation of integrins in the plasma membrane. (d) is assisted by motor proteins that pull on microtubules attached to the cell cortex.

a (requires ATP)

16-62 When Ras is activated, cells will divide. A dominant-negative form of Ras clings too tightly to GDP. You introduce a dominant-negative form of Ras into cells that also have a normal version of Ras. Which of the following statements is true? (a) The cells you create will divide less frequently than normal cells in response to the extracellular signals that typically activate Ras. (b) The cells you create will run out of the GTP necessary to activate Ras. (c) The cells you create will divide more frequently compared to normal cells in response to the extracellular signals that typically activate Ras. (d) The normal Ras in the cells you create will not be able to bind GDP because the dominant-negative Ras binds to GDP too tightly.

a (the cells you create will divide less frequently than normal cells in response to the extracellular signals that typically activate Ras)

16-38 Activated protein kinase C (PKC) can lead to the modification of the membrane lipids in the vicinity of the active PKC. Figure Q16-38 shows how G proteins can indirectly activate PKC. You have discovered the enzyme activated by PKC that mediates the lipid modification. You call the enzyme Rafty and demonstrate that activated PKC directly phosphorylates Rafty, activating it to modify the plasma membrane lipids in the vicinity of the cell where PKC is active; these lipid modifications can be detected by dyes that bind to the modified lipids. Cells lacking Rafty do not have these modifications, even when PKC is active. Which of the following conditions would lead to signal-independent modification of the membrane lipids by Rafty? Figure Q16-38 (a) the expression of a constitutively active phospholipase C (b) a mutation in the GPCR that binds the signal more tightly (c) a Ca2+ channel in the endoplasmic reticulum with an increased affinity for IP3 (d) a mutation in the gene that encodes Rafty such that the enzyme can no longer be phosphorylated by PKC

a (the expression of a constitutively active phospholipase C)

18-52 A friend declares that chromosomes are held at the metaphase plate by microtubules that push on each chromosome from opposite sides. Which of the following observations does not support your belief that the microtubules are pulling on the chromosomes? (a) the jiggling movement of chromosomes at the metaphase plate (b) the way in which chromosomes behave when the attachment between sister chromatids is severed (c) the way in which chromosomes behave when the attachment to one kinetochore is severed (d) the shape of chromosomes as they move toward the spindle poles at anaphase

a (the jiggling movement of chromosomes at the metaphase plate)

16-60 The ethylene response in plants involves a dimeric transmembrane receptor. When the receptor is not bound to ethylene, the receptor binds to and activates a protein kinase, which activates an intracellular signaling pathway that leads to the degradation of a transcriptional regulator important for transcribing the ethyleneresponsive genes (see Figure Q16-60). You discover a phosphatase that is important for ethylene signaling, and you name it PtpE. Plants lacking PtpE never turn on ethylene-responsive genes, even in the presence of ethylene. You find that PtpE dephosphorylates serine 121 on the transcriptional regulator. Furthermore, plants lacking PtpE degrade the transcriptional regulator in the presence of ethylene. Figure Q16-60 Which of the following statements is inconsistent with your data? (a) When the transcriptional regulator is phosphorylated, it activates transcription of the ethylene-responsive genes. (b) When the transcriptional regulator is not phosphorylated, it binds to DNA. (c) Activation of the protein kinase that binds to the ethylene receptor leads to inactivation of PtpE. (d) Binding of ethylene to its receptor leads to the activation of PtpE.

a (when the transcriptional regulator is phosphorylated, it activates transcription of the ethylene-responsive genes)

Consider the apical location of a particular protein A expressed in epithelial cells, illustrated in the Figure (A). When a molecule that chelates calcium is added to the cell culture medium, you observe a redistribution of that protein around the entire cell, shown in Figure (B). Which is most likely to be true about the role of calcium in maintaining an apical distribution of protein A?

a calcium is required to maintain the structural integrity of the junctional complex (tight complex)

Which of the following mechanisms best describes the manner in which lysozyme lowers the energy required for its substrate to reach its transition-state conformation?

by altering the shape of the substrate to mimic the conformation of the transition state

Fully folded proteins typically have polar side chains on their surfaces, where electrostatic attractions and hydrogen bonds can form between the polar group on the amino acid and the polar molecules in the solvent. In contrast, some proteins have a polar side chain in their hydrophobic interior. Which of the following would not occur to help accommodate an internal, polar side chain?

a hydrogen bond forms between a polar side chain and an aromatic side chain

The growth factor RGF stimulates proliferation of cultured rat cells. The receptor that binds RGF is a receptor tyrosine kinase called RGFR. Which of the following types of alteration to RGF would be most likely to prevent receptor dimerization?

a mutation that prevents RGFR from binding to RGF

Protein structures have several different levels of organization. The primary structure of a protein is its amino acid sequence. The secondary and tertiary structures are more complicated. Consider the definitions below and select the one that best fits the term "protein domain."

a protein segment that folds independently

a second messenger is

a substance that brings about a desired effect in a cell as a result of a hormone binding to its receptor on the cell surface

a second messenger is ------

a substance that brings about a desired effect in a cell as a result of a hormone binding to its receptor on the cell surface

example of apoptosis in an animal

a tadpole becomes a frog by losing it's tail. the tail dies off (by apoptosis) to become a frog

15-16 A large protein that passes through the nuclear pore must have an appropriate _________. (a) sorting sequence, which typically contains the positively charged amino acids lysine and arginine. (b) sorting sequence, which typically contains the hydrophobic amino acids leucine and isoleucine. (c) sequence to interact with the nuclear fibrils. (d) Ran-interacting protein domain.

a) sorting sequence, which typically contains the positively charged amino acids lysine and arginine.

G- protein coupled receptors

all receptors for this class are polypeptides with seven transmembrane domains

The hydrolysis of GTP to GDP carried out by tubulin molecules ________________.

allows the behavior of microtubules called dynamic instability

ion channel coupled receptors

alter the membrane potential directly by changing the permeability of the plasma

Studies conducted with a lysozyme mutant that contains an Asp to Asn change at position 52 and a Glu to Gln change at position 35 exhibited almost a complete loss in enzymatic activity. What is the most likely explanation for the decrease in enzyme activity in the mutant?

absence of negative charges in the active site

binding of the neurotransmitter ____ to its GPCR on the heart cells results in the activation of the G protein Gi. the _____ directly opens a ____ channel in the plasma membrane, increasing its permeability to ___ and thereby making the membrane harder to activate and ____ the heart rate. inactivation of the ____ by hydrolysis of its bound GTP returns the G protein to its inactive state, allowing the ___ channel to close

acetylcholine By complex K+ K+ lower K+

binding of the neurotransmitter ---------to its GPCR on the heart cells results in the activation of the G-protein , Gi. the -------directly opens a -------channel in the plasma membrane, increasing its permeability to -----------and thereby making the membrane harder to activate and ---------the heart rate. inactivation of the -------by hydrolysis of its bound GTP returns to its inactive state, allowing the -------channel to close

acetylcholine beta K+ K+ slow alpha subunit K+

an andrenaline activates a GPCR, which turns on a G-protein that activates --------to boost the production of cAMP. the increase in cAMP activates -------which phosphorylates and activates an enzyme called phosphorylase kinase. this kinase activates glycogen phosphorylase, the enzyme that breaks down glycogen. because these reactions do not involve changes in gene transcription or new protein synthesis, they occur ------

adenylyl cyclase PKA

an adrenaline activates a GPCR which turns on a G protein that activates ________ to boost the production of cyclic AMP

adenylyn cyclase

amino acid sequence

Viagra targets a specific isoform of cGMP phosphodiesterase. Phosphodiesterases are made out of

amino acids

16-19 Intracellular signaling proteins can __________________ the signal received to evoke a strong response from just a few extracellular signal molecules. A cell that receives more than one extracellular signal at the same time can __________________ this information using intracellular signaling proteins.

amplify; integrate

since the first nucleotides cannot be linked in a newly synthesized strand in DNA replication, ___ is required for initiation

an RNA primer

Membrane proteins, like membrane lipids, can move laterally by exchanging positions with other membrane components. Which type of membrane proteins is expected to be the least mobile, based on their function?

anchors

Cytoskeleton is particularly important in ____________ cells

animal

Indicate whether the following molecules are found in plants, animals, or both. Collagen

animals

Indicate whether the following molecules are found in plants, animals, or both. Intermediate filaments

animals

which of the following statements is true

another name for the fertilized egg cell is the zygote

BLANK helps regulate animal cell numbers

apoptosis

two ways that cells die

apoptosis necrosis

induced pluripotent stem (iPS) cells

are created by the expression of a set of key genes in cells derived from adult tissues so that these cells can differentiate into a variety of cell types

MicroRNAs ____________________.

are produced from a precursor miRNA transcript

16-34 During the mating process, yeast cells respond to pheromones secreted by other yeast cells. These pheromones bind GPCRs on the surface of the responding cell and lead to the activation of G proteins inside the cell. When a wild-type yeast cell senses the pheromone, its physiology changes in preparation for mating: the cell stops growing until it finds a mating partner. If yeast cells do not undergo the appropriate response after sensing a pheromone, they are considered sterile. Yeast cells that are defective in one or more components of the G protein have characteristic phenotypes in the absence and presence of the pheromone, which are listed in Table 16-34. Table Q16-34 Which of the following models is consistent with the data from the analysis of these mutants? Explain your answer. (a) α activates the mating response but is inhibited when bound to βγ (b) βγ activates the mating response but is inhibited when bound to α (c) the G protein is inactive; either free α or free βγ complex is capable of activating the mating response (d) the G protein is active; both free α and free βγ complex are required to inhibit the mating response

b (Beta v activates the mating response but is inhibited when bound to alpha)

16-54 Which of the following statements is true? (a) MAP kinase is important for phosphorylating MAP kinase kinase. (b) PI 3-kinase phosphorylates a lipid in the plasma membrane. (c) Ras becomes activated when an RTK phosphorylates its bound GDP to create GTP. (d) STAT proteins phosphorylate JAK proteins, which then enter the nucleus and activate gene transcription.

b (PI 3-Kinase phosphorylates a lipid in the plasma membrane)

16-18 Figure Q16-18 shows the pathway through which nitric oxide (NO) triggers smooth muscle relaxation in a blood-vessel wall. Which of the following situations would lead to relaxation of the smooth muscle cells in the absence of acetylcholine? Figure Q16-18 (a) a smooth muscle cell that has a defect in guanylyl cyclase such that it cannot bind NO (b) a muscle cell that has a defect in guanylyl cyclase such that it constitutively converts GTP to cyclic GMP (c) a muscle cell that has cyclic GMP phosphodiesterase constitutively active (d) a drug that blocks an enzyme involved in the metabolic pathway from arginine to NO

b (a muscle cell that has a defect in guanlyl cyclase such that it constitutively converts GTP to cyclic GMP)

16-46 The growth factor RGF stimulates proliferation of cultured rat cells. The receptor that binds RGF is a receptor tyrosine kinase called RGFR. Which of the following types of alteration would be most likely to prevent receptor dimerization? (a) a mutation that increases the affinity of RGFR for RGF (b) a mutation that prevents RGFR from binding to RGF (c) changing the tyrosines that are normally phosphorylated on RGFR dimerization to alanines (d) changing the tyrosines that are normally phosphorylated on RGFR dimerization to glutamic acid

b (a mutation that prevents RGFR from binding to RGF most likely prevents receptor dimerization)

16-52 Male cockroaches with mutations that strongly decrease the function of an RTK called RTKX are oblivious to the charms of their female comrades. This particular RTK binds to a small molecule secreted by sexually mature females. Most males carrying loss-of-function mutations in the gene for Ras protein are also unable to respond to females. You have just read a paper in which the authors describe how they have screened cockroaches that are mutant in RTKX for additional mutations that partly restore the ability of males to respond to females. These mutations decrease the function of a protein that the authors call Z. Which of the following types of protein could Z be? Explain your answer. (a) a protein that activates the Ras protein by causing Ras to exchange GDP for GTP (b) a protein that stimulates hydrolysis of GTP by the Ras protein (c) an adaptor protein that mediates the binding of the RTKX to the Ras protein (d) a transcriptional regulator required for the expression of the Ras gene

b (a protein that stimulates hydrolysis of GTP by the Ras protein)

16-50 You are interested in further understanding the signal transduction pathway that controls the production of Pig1, a protein important for regulating cell size. Activation of the TRK receptor leads to activation of the GTP-binding protein, Ras, which then activates a protein kinase that phosphorylates the SZE transcription factor. SZE only interacts with the nuclear transport receptor when it is phosphorylated. SZE is a gene activator for the Pig1 gene. This pathway is diagrammed in Figure Q16-50. Figure Q16-50 Normal cells grown under standard conditions (without ligand) are 14 µm in diameter while normal cells exposed to TRK ligand are 10.5 µm in diameter. Given this situation, which of the following conditions do you predict will more likely lead to smaller cells? (a) addition of TRK ligand and a drug that stimulates the GTPase activity of Ras (b) addition of TRK ligand and a drug that inhibits the activity of the phosphatase that acts on SZE (c) addition of TRK ligand and a drug that stimulates the degradation of Pig1 (d) addition of TRK ligand and a drug that inhibits Pig1 binding to DNA

b (addition of TRK ligand and a drug that inhibits the activity of phosphatase that acts on SZE)

18-34 Condensins ________________. (a) are degraded when cells enter M phase. (b) assemble into complexes on the DNA when phosphorylated by M-Cdk. (c) are involved in holding sister chromatids together. (d) bind to DNA before DNA replication begins.

b (assemble into complexes on the DNA when phosphorylate by M-Cdk)

18-30 You create cells with a version of Cdc6 that cannot be phosphorylated and thus cannot be degraded. Which of the following statements describes the likely consequence of this change in Cdc6? (a) Cells will enter S phase prematurely. (b) Cells will be unable to complete DNA synthesis. (c) The origin recognition complex (ORC) will be unable to bind to DNA. (d) Cdc6 will be produced inappropriately during M phase. b (cells will be unable to complete DNA synthesis)

b (cells will be unable to complete DNA synthesis)

16-57 The activation of the serine/threonine protein kinase Akt requires phosphoinositide 3-kinase (PI 3-kinase) to _________. (a) activate the RTK. (b) create phosphorylated lipids that serve as docking sites that localize Akt to the plasma membrane. (c) directly phosphorylate Akt. (d) to create DAG

b (create phosphorylated lipids that serve as docking sites that localize Akt to the plasma membrane)

18-58 A cell with nuclear lamins that cannot be phosphorylated in M phase will be unable to ________________. (a) reassemble its nuclear envelope at telophase. (b) disassemble its nuclear lamina at prometaphase. (c) begin to assemble a mitotic spindle. (d) condense its chromosomes at prophase

b (disassemble its nuclear lamina at prometaphase)

18-64 Which organelle fragments during mitosis? (a) endoplasmic reticulum (b) Golgi apparatus (c) mitochondrion (d) chloroplast

b (golgi apparatus fragments)

16-15 Acetylcholine is a signaling molecule that elicits responses from heart muscle cells, salivary gland cells, and skeletal muscle cells. Which of the following statements is false? (a) Heart muscle cells decrease their rate and force of contraction when they receive acetylcholine, whereas skeletal muscle cells contract. (b) Heart muscle cells, salivary gland cells, and skeletal muscle cells all express an acetylcholine receptor that belongs to the transmitter-gated ion channel family. (c) Active acetylcholine receptors on salivary gland cells and heart muscle cells activate different intracellular signaling pathways. (d) Heart muscle cells, salivary gland cells, and skeletal muscle cells all respond to acetylcholine within minutes of receiving the signal.

b (heart muscle cells, salivary gland cells, and skeletal muscle cells all express an acetylcholine receptor that belongs to the transmitter-gated ion channel family)

16-5 When a signal needs to be sent to most cells throughout a multicellular organism, the signal most suited for this is a ___________. (a) neurotransmitter. (b) hormone. (c) dissolved gas. (d) scaffold

b (hormone)

18-3 A mutant yeast strain stops proliferating when shifted from 25°C to 37°C. When these cells are analyzed at the two different temperatures, using a machine that sorts cells according to the amount of DNA they contain, the graphs in Figure Q18-3 are obtained. Figure 18-3 Which of the following would not explain the results with the mutant? (a) inability to initiate DNA replication (b) inability to begin M phase (c) inability to activate proteins needed to enter S phase (d) inappropriate production of a signal that causes the cells to remain in G1

b (inability to begin M phase)

18-14 You have isolated a strain of mutant yeast cells that divides normally at 30°C but cannot enter M phase at 37°C. You have isolated its mitotic cyclin and mitotic Cdk and find that both proteins are produced and can form a normal M-Cdk complex at both temperatures. Which of the following temperature-sensitive mutations could not be responsible for the behavior of this strain of yeast? (a) inactivation of a protein kinase that acts on the mitotic Cdk kinase (b) inactivation of an enzyme that ubiquitylates M cyclin (c) inactivation of a phosphatase that acts on the mitotic Cdk kinase (d) a decrease in the levels of a transcriptional regulator required for producing sufficient amounts of M cyclin

b (inactivation of an enzyme that ubiquitylates M cyclin)

18-4 Which of the following events does not usually occur during interphase? (a) Cells grow in size. (b) The nuclear envelope breaks down. (c) DNA is replicated. (d) The centrosomes are duplicated.

b (nuclear envelope does not break down during interphase)

16-59

b (plants (fungi and animals))

16-1 Cell lines A and B both survive in tissue culture containing serum but do not proliferate. Factor F is known to stimulate proliferation in cell line A. Cell line A produces a receptor protein (R) that cell line B does not produce. To test the role of receptor R, you introduce this receptor protein into cell line B, using recombinant DNA techniques. You then test all of your various cell lines in the presence of serum for their response to factor F, with the results summarized in Table Q16-1. Table Q16-1 Which of the following cannot be concluded from your results above? (a) Binding of factor F to its receptor is required for proliferation of cell line A. (b) Receptor R binds to factor F to induce cell proliferation in cell line A. (c) Cell line A expresses a receptor for factor F. (d) Factor F is not required for proliferation in cell line B

b (receptor r binds to factor f to induce cell proliferation in cell line A)

18-11 Progression through the cell cycle requires a cyclin to bind to a Cdk because _________. (a) the cyclins are the molecules with the enzymatic activity in the complex. (b) the binding of a cyclin to Cdk is required for Cdk enzymatic activity. (c) cyclin binding inhibits Cdk activity until the appropriate time in the cell cycle. (d) without cyclin binding, a cell-cycle checkpoint will be activated.

b (the binding of a cyclin to Cdk is required for Cdk enzymatic activity)

18-28 Which of the following statements is false? (a) DNA synthesis begins at origins of replication. (b) The loading of the origin recognition complexes (ORCs) is triggered by SCdk. (c) The phosphorylation and degradation of Cdc6 help to ensure that DNA is replicated only once in each cell cycle. (d) DNA synthesis can only begin after prereplicative complexes assemble on the ORCs.

b (the loading of the origin recognition complexes (ORCs) is triggered by SCdk)

16-7 Which of the following statements is true? (a) Because endocrine signals are broadcast throughout the body, all cells will respond to the hormonal signal. (b) The regulation of inflammatory responses at the site of an infection is an example of paracrine signaling. (c) Paracrine signaling involves the secretion of signals into the bloodstream for distribution throughout the organism. (d) The axons of neurons typically signal target cells using membrane-bound signaling molecules that act on receptors in the target cells.

b (the regulation of inflammatory responses at the site of an infection is an example of paracrine signaling)

What part of the DNA replication process would be most directly affected if an organism had a mutation that meant it was lacking primase?

initiation of DNA synthesis

Two cell lines, A and B, both survive but do not divide when they are cultured in vitro with a medium containing serum. Factor F is a protein that is known to stimulate cell division in cell line A. Cell line A produces a receptor protein (R) that cell line B does not produce. To test the role of receptor R, you introduce this receptor protein into cell line B, using recombinant DNA techniques. You then test all of your various cell lines in the presence of serum for their response to factor F, with the results summarized in the table below. Cell Line Factor F Added Response A - No division A + Division B - No Division B + No Division B + Receptor R - Division B + Receptor R + Division Which of the following cannot be concluded from your results above? a.) Binding of factor F to its receptor is required for proliferation of cell line A. b.) Receptor R binds to factor F to induce cell proliferation in cell line A. c.) Cell line A expresses a receptor for factor F. d.) Factor F is not required for proliferation in cell line B.

b.) Receptor R binds to factor F to induce cell proliferation in cell line A.

Sickle-cell anemia is an example of an inherited disease. Individuals with this disorder have misshapen (sickle-shaped) red blood cells caused by a change in the sequence of the β-globin gene. What is the nature of the change?

base-pair change

. The human genome encodes about 24,000 genes. The typical differentiated human cell expresses _________________ at any one time?

between 5000 and 15,000 genes

the following reactions are all common parts of some hormone process: what is the right sequence binding of the hormone to the receptor synthesis of cyclic AMP phosphorylation of the target enzyme release of a Gprotein from the interior cell enzyme activation of protein kinase

bind, release, synthesise, activate, phosphorylate

The _______________ nature of a myosin thick filament is essential for muscle contraction.

bipolar

Indicate whether the following molecules are found in plants, animals, or both. Microtubules

both

16-61 Figure Q16-61 shows that intracellular signaling pathways can be highly interconnected. Figure Q16-61 From the information in Figure Q16-61, which of the following statements is incorrect? (a) The GPCR and the RTK both activate phospholipase C. (b) Activation of either the GPCR or the RTK will lead to activation of transcriptional regulators. (c) CaM-kinase is only activated when the GPCR is active and not when the RTK is active. (d) Ras is activated only when the RTK is active and not when the GPCR is active

c (CaM-kinase is only activated when the GPCR is active and not when the RTK is active)

18-15 You engineer yeast cells that express the M cyclin during S phase by replacing the promoter sequence of the M cyclin gene with that of S cyclin. Keeping in mind that yeast cells have one common Cdk that binds to all cyclins, which of the following outcomes is least likely during this experiment? (a) There will be both M cyclin-Cdk and S cyclin-Cdk complexes in the cell during S phase. (b) Some substrates that are normally phosphorylated in M phase will now be phosphorylated in S phase. (c) G1 cyclins will be expressed during S phase. (d) S-Cdk targets will be phosphorylated during S phase

c (G1 cyclins will be expressed during S phase is not a likely outcome)

16-13 The lab you work in has discovered a previously unidentified extracellular signal molecule called QGF, a 75,000-dalton protein. You add purified QGF to different types of cells to determine its effect on these cells. When you add QGF to heart muscle cells, you observe an increase in cell contraction. When you add it to fibroblasts, they undergo cell division. When you add it to nerve cells, they die. When you add it to glial cells, you do not see any effect on cell division or survival. Given these observations, which of the following statements is most likely to be true? (a) Because it acts on so many diverse cell types, QGF probably diffuses across the plasma membrane into the cytoplasm of these cells. (b) Glial cells do not have a receptor for QGF. (c) QGF activates different intracellular signaling pathways in heart muscle cells, fibroblasts, and nerve cells to produce the different responses observed. (d) Heart muscle cells,

c (QCF activates different intracellular signaling pathways in heart muscle cells, fibroblasts, and nerve cells to produce the different responses observed)

18-23 The Retinoblastoma (Rb) protein blocks cells from entering the cell cycle by ______. (a) phosphorylating Cdk. (b) marking cyclins for destruction by proteolysis. (c) inhibiting cyclin transcription. (d) activating apoptosis.

c (Rb inhibiting cyclin transcription)

16-35 You are interested in how cyclic-AMP-dependent protein kinase A (PKA) functions to affect learning and memory, and you decide to study its function in the brain. It is known that, in the cells you are studying, PKA works via a signal transduction pathway like the one depicted in Figure Q16-35. Furthermore, it is also known that activated PKA phosphorylates the transcriptional regulator called Nerd that then activates transcription of the gene Brainy. Which situation described below will lead to an increase in Brainy transcription? Figure Q16-35 (a) a mutation in the Nerd gene that produces a protein that cannot be phosphorylated by PKA (b) a mutation in the nuclear import sequence of PKA from PPKKKRKV to PPAAAAAV (c) a mutation in the gene that encodes cAMP phosphodiesterase that makes the enzyme inactive (d) a mutation in the gene that encodes adenylyl cyclase that renders the enzyme unable to interact with the α subunit of the G protein

c (a mutation in the gene that encodes cAMP phosphodiesterase that makes the enzyme inactive)

16-45 The growth factor Superchick stimulates the proliferation of cultured chicken cells. The receptor that binds Superchick is a receptor tyrosine kinase (RTK), and many chicken tumor cell lines have mutations in the gene that encodes this receptor. Which of the following types of mutation would be expected to promote uncontrolled cell proliferation? (a) a mutation that prevents dimerization of the receptor (b) a mutation that destroys the kinase activity of the receptor (c) a mutation that inactivates the protein tyrosine phosphatase that normally removes the phosphates from tyrosines on the activated receptor (d) a mutation that prevents the binding of the normal extracellular signal to the receptor

c (a mutation that inactivates the protein tyrosine phosphatase that normally removes the phosphates from tyrosines on the activated receptor)

16-63 Figure Q16-63 shows how normal signaling works with a Ras protein acting downstream of an RTK. You examine a cell line with a constitutively active Ras protein that is always signaling. Which of the following conditions will turn off signaling in this cell line? Figure Q16-63 (a) addition of a drug that prevents protein X from activating Ras (b) addition of a drug that increases the affinity of protein Y and Ras (c) addition of a drug that blocks protein Y from interacting with its target (d) addition of a drug that increases the activity of protein Y

c (addition of a drug that blocks protein Y from interacting with its target)

18-35 At the end of DNA replication, the sister chromatids are held together by the ___________. (a) kinetochores. (b) securins. (c) cohesins. (d) histones.

c (at the end of DNA replication, the sister chromatids are held together by the cohesions)

18-66 Apoptosis differs from necrosis in that necrosis ________________. (a) requires the reception of an extracellular signal. (b) causes DNA to fragment. (c) causes cells to swell and burst, whereas apoptotic cells shrink and condense. (d) involves a caspase cascade

c (causes cells to swell and burst, whereas apoptotic cells shrink and condense)

16-17 The local mediator nitric oxide stimulates the intracellular enzyme guanylyl cyclase by ________________. (a) activating a G protein. (b) activating a receptor tyrosine kinase. (c) diffusing into cells and stimulating the cyclase directly. (d) activating an intracellular protein kinase.

c (diffusing into cells and stimulating the cyclase directly)

18-13 The concentration of mitotic cyclin (M cyclin) ________________. (a) rises markedly during M phase. (b) is activated by phosphorylation. (c) falls toward the end of M phase as a result of ubiquitylation and degradation. (d) is highest in G1 phase.

c (falls toward the end of M phase as a result of ubiquitylation and degradation)

16-26 Foreign substances like nicotine, morphine, and menthol exert their initial effects by _____. (a) killing cells immediately, exerting their physiological effects by causing cell death. (b) diffusing through cell plasma membranes and binding to transcription factors to change gene expression. (c) interacting with cell-surface receptors, causing the receptors to transduce signal inappropriately in the absence of the normal stimulus. (d) removing cell-surface receptors from the plasma membrane.

c (interacting with cell-surface receptors, causing the receptors to transduce signal inappropriately in the absence of the normal stimulus)

16-47 A protein kinase can act as an integrating device in signaling if it ___________________. (a) phosphorylates more than one substrate. (b) catalyzes its own phosphorylation. (c) is activated by two or more proteins in different signaling pathways. (d) initiates a phosphorylation cascade involving two or more protein kinases

c (is activated by two or more proteins in different signaling pathways)

18-54 Which of the following statements about the anaphase-promoting complex (APC) is false? (a) It promotes the degradation of proteins that regulate M phase. (b) It inhibits M-Cdk activity. (c) It is continuously active throughout the cell cycle. (d) M-Cdk stimulates its activity.

c (it is continuously active throughout the cell cycle)

18-29 How does S-Cdk help guarantee that replication occurs only once during each cell cycle? (a) It blocks the rise of Cdc6 concentrations early in G1. (b) It phosphorylates and inactivates DNA helicase. (c) It phosphorylates the Cdc6 protein, marking it for destruction. (d) It promotes the assembly of a prereplicative complex.

c (it phosphorylates the Cdc6 protein, marking it for destruction)

16-29 The following happens when a G-protein-coupled receptor activates a G protein. (a) The β subunit exchanges its bound GDP for GTP. (b) The GDP bound to the α subunit is phosphorylated to form bound GTP. (c) The α subunit exchanges its bound GDP for GTP. (d) It activates the α subunit and inactivates the βγ complex.

c (the alpha subunit exchanges its bound GDP for GTP)

18-9 Which of the following descriptions is consistent with the behavior of a cell that lacks a protein required for a checkpoint mechanism that operates in G2? (a) The cell would be unable to enter M phase. (b) The cell would be unable to enter G2. (c) The cell would enter M phase under conditions when normal cells would not. (d) The cell would pass through M phase more slowly than normal cells

c (the cell would enter M phase under conditions when normal cells would not)

Nitric Oxide (NO) released from endothelial cells can result in the relaxation of underlying smooth muscle cells in vascular tissue. NO stimulates the intracellular enzyme guanylyl cyclase by: a.) activating a G protein. b.) activating a receptor tyrosine kinase. c.) diffusing into cells and stimulating the cyclase directly. d.) activating an intracellular protein kinase.

c.) diffusing into cells and stimulating the cyclase directly.

binding of an adrenaline molecule to its GPCR can lead to the activation of adenylyl cyclase and a rise in the concentration of ---------the increase in cAMP activates -------which the moves into the --------and phosphorylates specific transcription regulators.

cAMP PKA cystoso

a pluripotent cell

can give rise to all the tissues and cell types in the body

cells that are terminally differentiated

can no longer undergo cell division

if you activate BLANK, you can't do anything to stop is..

cascade

order of replacement times, from shortest to longest:

cell lining in the gut, epidermal cell, red blood cell, bone matrix, nerve cell

the principal microtubule-organizing center in animal cells is the

centrosome

clathrin

At the end of DNA replication, the sister chromatids are held together by the

cohesins

which of the following is not a feature commonly observed in beta sheets?

coiled-coil patterns

18-18 The components of MPF are evolutionarily __________________ from yeast to humans, so that the corresponding human genes are __________________ to function in yeast.

conserved able

15-58 For each of the following sentences, choose one of the two options enclosed in square brackets to make a correct statement. New plasma membrane reaches the plasma membrane by the [regulated/constitutive] exocytosis pathway. New plasma membrane proteins reach the plasma membrane by the [regulated/constitutive] exocytosis pathway. Insulin is secreted from pancreatic cells by the [regulated/constitutive] exocytosis pathway. The interior of the trans Golgi network is [acidic/alkaline]. Proteins that are constitutively secreted [aggregate/do not aggregate] in the trans Golgi network.

constitutive constitutive regulated acidic do not aggregate

Plasma membranes are extremely thin and fragile, requiring an extensive support network of fibrous proteins. This network is called the ____________.

cortex

caffeine acts as a stimulant by inhibiting what?

cyclic AMP phosphodiesterase in the nervous system blocking cyclic AMP degradation and keeping the concentration of cyclic AMP high

18-18 The regulatory component of MPF, called __________________, has a __________________ effect on MPF activity and plays a part in regulating interactions with its __________________s.

cyclin stimulatory substrates

18-32 The cell-cycle control system relies on sharp increases in the activities of regulatory proteins called __________________, or __________________, to trigger S phase and M phase. Inactivation of __________________ is required to exit from M phase after chromosome segregation.

cyclin-dependent kinases Cdks M-Cdk

how does necrosis happen?

cytoplasm leaks out and inflammation occurs

cytosol

The __________________ makes up about half of the total cell volume of a typical eukaryotic cell.

cytosol

New membrane phospholipids are synthesized by enzymes bound to the _____________ side of the _________________ membrane.

cytosolic, endoplasmic reticulum

18-41 Which word or phrase below best describes the phase in mitosis depicted in Figure Q18-41? (a) anaphase (b) prometaphase (c) S-phase checkpoint (d) metaphase

18-19 MPF activity was discovered when cytoplasm from a Xenopus M-phase cell was injected into Xenopus oocytes, inducing the oocytes to form a mitotic spindle. In a control experiment, Xenopus interphase cytoplasm was injected into oocytes and shown not to induce the formation of a mitotic spindle. Which of the following statements is not a legitimate conclusion from the control experiment? (a) The piercing of the oocyte membrane by a needle is insufficient to cause mitotic spindle formation. (b) An increased volume of cytoplasm is insufficient to cause mitotic spindle formation. (c) Injection of extra RNA molecules is insufficient to cause mitotic spindle formation. (d) Components of an interphase nucleus are insufficient to cause mitotic spindle formation.

d (COMPONENTs of an interphase nucleus are insufficient to cause mitotic spindle formation)

18-55 Which of the following statements is true? (a) Anaphase A must be completed before anaphase B can take place. (b) In cells in which anaphase B predominates, the spindle will elongate much less than in cells in which anaphase A dominates. (c) In anaphase A, both kinetochore and interpolar microtubules shorten. (d) In anaphase B, microtubules associated with the cell cortex shorten.

d (In anaphase B, microtubules associated with the cell cortex shorten)

16-36 Adrenaline stimulates glycogen breakdown in skeletal muscle cells by ultimately activating glycogen phosphorylase, the enzyme that breaks down glycogen, as depicted in Figure Q16-36. Figure Q16-36 Which of the following statements is false? (a) A constitutively active mutant form of PKA in skeletal muscle cells would lead to a decrease in the amount of unphosphorylated phosphorylase kinase. (b) A constitutively active mutant form of PKA in skeletal muscle cells would not increase the affinity of adrenaline for the adrenergic receptor. (c) A constitutively active mutant form of PKA in skeletal muscle cells would lead to an excess in the amount of glucose available. (d) A constitutively active mutant form of PKA in skeletal muscle cells would lead to an excess in the amount of glycogen available.

d (a constitutevely active mutant form of PKA in skeletal muscle cells would lead to an excess in the amount of GLYCOGEN available)

18-56 When introduced into mitotic cells, which of the following is expected to impair anaphase B but not anaphase A? (a) an antibody against myosin (b) ATPγS, a nonhydrolyzable ATP analog that binds to and inhibits ATPases (c) an antibody against the motor proteins that move from the plus end of microtubules to the minus end (d) an antibody against the motor proteins that move from the minus end of microtubules toward the plus end

d (an antibody against the motor proteins that move from the minus end of microtubules toward the plus end)

18-67 Which of the following statements about apoptosis is true? (a) Cells that constitutively express Bcl2 will be more prone to undergo apoptosis. (b) The prodomain of procaspases contains the catalytic activity necessary for procaspase activation. (c) Bax and Bak promote apoptosis by binding to procaspases in the apoptosome. (d) Apoptosis is promoted by the release of cytochrome c into the cytosol from mitochondria

d (apoptosis is promoted by the release of cytochrome c into the cytosol from mitochondria)

18-5 In which phase of the cell cycle do cells check to determine whether the DNA is fully and correctly replicated? (a) at the transition between G1 and S (b) when cells enter G0 (c) during M (d) at the end of G2

d (cells check to determine whether the DNA is fully and correctly replicated at the end of G2)

18-12 Levels of Cdk activity change during the cell cycle, in part because ________________. (a) the Cdks phosphorylate each other. (b) the Cdks activate the cyclins. (c) Cdk degradation precedes entry into the next phase of the cell cycle. (d) cyclin levels change during the cycle. d (cyclin levels change during the cycle)

d (cyclin levels change during the cycle)

16-6 During nervous-system development in Drosophila, the membrane-bound protein Delta acts as an inhibitory signal to prevent neighboring cells from developing into neuronal cells. Delta is involved in ______________ signaling. (a) endocrine (b) paracrine (c) neuronal (d) contact-dependent

d (delta is involved in CONTACT-DEPENDENT signaling)

16-10 Which of the following statements is false? (a) Nucleotides and amino acids can act as extracellular signal molecules. (b) Some signal molecules can bind directly to intracellular proteins that bind DNA and regulate gene transcription. (c) Some signal molecules are transmembrane proteins. (d) Dissolved gases such as nitric oxide (NO) can act as signal molecules, but because they cannot interact with proteins they must act by affecting membrane lipids.

d (dissolved gases such as nitric oxide (NO) can act as signal molecules, but because they cannot interact with proteins they must act by affecting membrane lipids)

16-58 Akt promotes the survival of many cells by affecting the activity of Bad and Bcl2, as diagrammed in Figure Q16-58. Figure Q16-58 Which of the following statements is false? (a) In the presence of a survival signal, Akt is phosphorylated. (b) In the absence of a survival signal, Bad inhibits the cell-death inhibitor protein Bcl2. (c) In the presence of a survival signal, the cell-death inhibitory protein Bcl2 is active. (d) In the absence of a survival signal, Bad is phosphorylated.

d (in the absence of a survival signal, bad is phosphorylated)

16-11 All members of the steroid hormone receptor family __________________. (a) are cell-surface receptors. (b) do not undergo conformational changes. (c) are found only in the cytoplasm. (d) interact with signal molecules that diffuse through the plasma membrane.

d (interact with signal molecules that diffuse through the plasma membrane)

18-25 The G1 DNA damage checkpoint ________________. (a) causes cells to proceed through S phase more quickly. (b) involves the degradation of p53. (c) is activated by errors caused during DNA replication. (d) involves the inhibition of cyclin-Cdk complexes by p21.

d (involves the inhibition of cyclin-Cdk complexes by p21.)

18-63 Which of the following statements is false? (a) Cytokinesis in plant cells is mediated by the microtubule cytoskeleton. (b) Small membrane vesicles derived from the Golgi apparatus deliver new cell-wall material for the new wall of the dividing cell. (c) The phragmoplast forms from the remains of interpolar microtubules of the mitotic spindle. (d) Motor proteins walking along the cytoskeleton are important for the contractile ring that guides formation of the new cell wall. d (motor proteins walking along the cytoskeleton are important for the contractile ring that guides formation of the new cell wall)

d (motor proteins walking along the cytoskeleton are important for the contractile ring that guides formation of the new cell wall)

18-48 Disassembly of the nuclear envelope ________________. (a) causes the inner nuclear membrane to separate from the outer nuclear membrane. (b) results in the conversion of the nuclear envelope into protein-free membrane vesicles. (c) is triggered by the phosphorylation of integrins. (d) must occur for kinetochore microtubules to form in animal cells.

d (must occur for kinetochore microtubules to form in animal cells)

16-31 The length of time a G protein will signal is determined by _______. (a) the activity of phosphatases that turn off G proteins by dephosphorylating Gα. (b) the activity of phosphatases that turn GTP into GDP. (c) the degradation of the G protein after Gα separates from Gβγ. (d) the GTPase activity of Gα.

d (the GTPase activity of Galpha)

18-17 Which of the following statements is false? (a) Mitotic Cdk must be phosphorylated by an activating kinase (Cak) before it is active. (b) Phosphorylation of mitotic Cdk by the inhibitory kinase (Wee1) makes the Cdk inactive, even if it is phosphorylated by the activating kinase. (c) Active M-Cdk phosphorylates the activating phosphatase (Cdc25) in a positive feedback loop. (d) The activating phosphatase (Cdc25) removes all phosphates from mitotic Cdk so that M-Cdk will be active.

d (the activating phosphatase (Cdc25) removes all phosphates from mitotic Cdk so that M-Cdk will be active)

18-2 What would be the most obvious outcome of repeated cell cycles consisting of S phase and M phase only? (a) Cells would not be able to replicate their DNA. (b) The mitotic spindle could not assemble. (c) Cells would get larger and larger. (d) The cells produced would get smaller and smaller.

d (the cells produced would get smaller and smaller)

18-62 Which of the following statements is false? (a) The cleavage furrow is a puckering of the plasma membrane caused by the constriction of a ring of filaments attached to the plasma membrane. (b) The cleavage furrow will not begin to form in the absence of a mitotic spindle. (c) The cleavage furrow always forms perpendicular to the interpolar microtubules. (d) The cleavage furrow always forms in the middle of the cell.

d (the cleavage furrow always forms in the MIDDLE of the cell)

16-30 Which of the following statements about G-protein-coupled receptors (GPCRs) is false? (a) GPCRs are the largest family of cell-surface receptors in humans. (b) GPCRs are used in endocrine, paracrine, and neuronal signaling. (c) GPCRs are found in yeast, mice, and humans. (d) The different classes of GPCR ligands (proteins, amino acid derivatives, or fatty acids) bind to receptors with different numbers of transmembrane domains.

d (the different classes of GPCR ligands (proteins, amino acid derivatives, or fatty acids) bind to receptors with different numbers of transmembrane domains)

18-36 Which of the following statements is true? (a) The mitotic spindle is largely made of intermediate filaments. (b) The contractile ring is made largely of microtubules and actin filaments. (c) The contractile ring divides the nucleus in two. (d) The mitotic spindle helps segregate the chromosomes to the two daughter cells.

d (the mitotic spindle helps segregate the chromosomes to the two daughter cells)

18-20 Which of the following is not good direct evidence that the cell-cycle control system is conserved through billions of years of divergent evolution? (a) A yeast cell lacking a Cdk function can use the human Cdk to substitute for its missing Cdk during the cell cycle. (b) The amino acid sequences of cyclins in plants are similar to the amino acid sequences of cyclins in humans. (c) The Cdk proteins in humans share conserved phosphorylation sites with the Cdk proteins in yeast. (d) Yeast cells have only one Cdk, whereas humans have many Cdks.

d (yeast cells have only one Cdk, whereas humans have many Cdks)

All members of the steroid hormone receptor family: a.) are cell-surface receptors. b.) do not undergo conformational changes upon steroid hormone binding. c.) are found exclusively in the cytoplasm. d.) interact with signal molecules that diffuse through the plasma membrane. e.) result in very rapid changes in cellular behavior upon steroid hormone binding.

d.) interact with signal molecules that diffuse through the plasma membrane.

16-33 Acetylcholine acts at a GPCR on heart muscle to make the heart beat more slowly. It does so by ultimately opening K+ channels in the plasma membrane (as diagrammed in Figure Q16-32), which decreases the cell's excitability by making it harder to depolarize the plasma membrane. Indicate whether each of the following conditions would increase or decrease the effect of acetylcholine. A. addition of a drug that stimulates the GTPase activity of the Gα subunit B. mutations in the K+ channel that keep it closed all the time C. modification of the Gα subunit by cholera toxin D. a mutation that decreases the affinity of the βγ complex of the G protein for the K+ channel E. a mutation in the acetylcholine receptor that prevents its localization on the cell surface F. adding acetylcholinesterase to the external environment of the cell

decrease decrease increase decrease decrease decrease

Do all cells types respond to acetylcholine similarly or differently?

differently

enzyme coupled receptors

discovered for their role in responding to growth factors in animal cells

15-37 For each of the following sentences, fill in the blanks with the best word or phrase selected from the list below. Not all words or phrases will be used; use each word or phrase only once. Proteins are transported out of a cell via the *secretory* or *exocytic* pathway. Fluids and macromolecules are transported into the cell via the *endocytic* pathway. All proteins being transported out of the cell pass through the *endoplasmic reticulum* and the *Golgi apparatus*. Transport vesicles link organelles of the *endomembrane* system. The formation of __________________ in the endoplasmic reticulum stabilizes protein structure. carbohydrate Golgi apparatus disulfide bonds hydrogen bonds endocytic ionic bonds endomembrane lysosome endoplasmic reticulum protein endosome secretory exocytic

disulfide bonds

which of the following statements is true

disulfide bonds stabilize but do not change a protein's final conformation

Which of the following questions would not be answered by using karyotyping?

do any chromosomes contain point mutations?

You are a virologist interested in studying the evolution of viral genomes. You are studying two newly isolated viral strains and have sequenced their genomes. You find that the genome of strain 1 contains 25% A, 55% G, 20% C, and 10% T. You report that you have isolated a virus with a single-stranded DNA genome. Based on what evidence can you make this conclusion?

double-stranded genomes have equal amounts of A and T

Cilia and flagella use _______________ motors to create movement?

dynein

18-42 Which letter is associated with the line that is pointing to the interpolar microtubules in Figure Q18-41? (a) A (b) B (c) C (d) D (e) E

DNA replication is considered semiconservative because ______________.

each daughter DNA molecule consists of one strand from the parent DNA molecule and one new strand

18-18 Many features of __________________ cells make them suitable for biochemical studies of the cell-cycle control system. For example, the cells are unusually large and are arrested in a __________________-like phase. When the cells are triggered to resume cycling, the cell divisions have especially __________________ G1 and G2 phases and occur __________________.

egg G2 short synchronously

how do reproductive and therapeutic cloning differ

embryos are placed into foster mothers during reproductive cloning, but not during therapeutic cloning

16-2 Cells can signal to each other in various ways. A signal that must be relayed to the entire body is most efficiently sent by __________________ cells, which produce hormones that are carried throughout the body through the bloodstream. On the other hand, __________________ methods of cell signaling do not require the release of a secreted molecule and are used for very localized signaling events.

endocrine; contact-dependent;

endocytic

15-37 For each of the following sentences, fill in the blanks with the best word or phrase selected from the list below. Not all words or phrases will be used; use each word or phrase only once. Proteins are transported out of a cell via the *secretory* or *exocytic* pathway. Fluids and macromolecules are transported into the cell via the *endocytic* pathway. All proteins being transported out of the cell pass through the *endoplasmic reticulum* and the *Golgi apparatus*.Transport vesicles link organelles of the __________________ system. carbohydrate Golgi apparatus disulfide bonds hydrogen bonds endocytic ionic bonds endomembrane lysosome endoplasmic reticulum protein endosome secretory exocytic

endomembrane

15-37 For each of the following sentences, fill in the blanks with the best word or phrase selected from the list below. Not all words or phrases will be used; use each word or phrase only once. Proteins are transported out of a cell via the *secretory* or *exocytic* pathway. Fluids and macromolecules are transported into the cell via the *endocytic* pathway All proteins being transported out of the cell pass through the __________________ carbohydrate Golgi apparatus disulfide bonds hydrogen bonds endocytic ionic bonds endomembrane lysosome endoplasmic reticulum protein endosome secretory exocytic

endoplasmic reticulum

15-5 For each of the following sentences, fill in the blanks with the best word or phrase selected from the list below. Not all words or phrases will be used; use each word or phrase only once. The *cytosol*makes up about half of the total cell volume of a typical eukaryotic cell. Ingested materials within the cell will pass through a series of compartments called *endosomes* on their way to the *lysosome*_, which contains digestive enzymes and will ultimately degrade the particles and macromolecules taken into the cell and will also degrade worn-out organelles. The *Golgi apparatus* has a cis and trans face and receives proteins and lipids from the __________________, a system of interconnected sacs and tubes of membranes that typically extends throughout the cell. cytosol Golgi apparatus nucleus endoplasmic reticulum lysosome peroxisomes endosomes mitochondria plasma membrane

endoplasmic reticulum,

All proteins being transported out of the cell pass through the __________________ and the __________________.

endoplasmic reticulum, golgi apparatus

endoplasmic reticulum.

endosome

After these vesicles have pinched off from the plasma membrane, they will fuse with the __________________, where materials that are taken into the vesicle are sorted. A second type of endocytosis is __________________, which is used to take up large vesicles that can contain microorganisms and cellular debris

endosome, phagocytosis

endosomes

Ingested materials within the cell will pass through a series of compartments called __________________ on their way to the __________________, which contains digestive enzymes and will ultimately degrade the particles and macromolecules taken into the cell and will also degrade worn-out organelles.

endosomes, lysosome

Mitochondria contain their own genome, are able to duplicate, and actually divide on a different time line from the rest of the cell. Nevertheless, mitochondria cannot function for long when isolated from the cell because they are __________________.

endosymbionts

3 main classes of cell surface receptors

enzyme coupled receptors ion channel coupled receptors G protein coupled receptors

what are caspases?

enzymes that program cell death

Aminoacyl-tRNA synthetases are ___________________.

enzymes that synthesize tRNAs

During transcription in __________________ cells, transcriptional regulators that bind to DNA thousands of nucleotides away from a gene's promoter can affect a gene's transcription.

eucaryotic

exocytic

all cell surface receptor proteins bind to a(n) _____________ and transduce its message into one or more intracellular signaling molecules that alter the cell's behavior

extracellular signal molecule

what does myostatin do?

inhibits muscle formation

"Nonpolar interactions" is simply another way of saying "van der Waals attractions."

false

Phosphatidylserine is the most abundant type of phospholipid found in cell membranes.

false

Sister chromatids are held together by condensins from the time they arise by DNA replication until the time they separate at anaphase.

false

a disaccharide consists of a sugar covalently linked to another molecules such as an amino acid or a nucleotide

false

in eukaryotes, all membrane-enclosed organelles are surrounded by one lipid bilayer.

false

the terms prokaryote and bacterium are synonyms

false

18-45 Before chromosomes segregate in M phase, they and the segregation machinery must be appropriately prepared. Indicate whether the following statements are true or false. If false, change a single noun to make the statement true. A. Sister chromatids are held together by condensins from the time they arise by DNA replication until the time they separate at anaphase. B. Cohesins are required to make the chromosomes more compact and thus to prevent tangling between different chromosomes. C. The mitotic spindle is composed of actin filaments and myosin filaments. D. Microtubule-dependent motor proteins and microtubule polymerization and depolymerization are mainly responsible for the organized movements of chromosomes during mitosis. E. The centromere nucleates a radial array of microtubules called an aster, and its duplication is triggered by S-Cdk. F. Each centrosome contains a pair of centrioles and hundreds of γ-tubulin rings that nucleate the growth of microtubules.

false false false false true

Membrane synthesis in the cell requires the selective retention of certain types of lipids on one side or the other. Which group of enzymes accomplishes this task?

flippases

15-9 For each of the following sentences, fill in the blanks with the best word or phrase selected from the list below. Not all words or phrases will be used; use each word or phrase only once. Plasma membrane proteins are inserted into the membrane in the *endoplasmic reitculum*. The address information for protein sorting in a eukaryotic cell is contained in the *amino acid sequence* of the proteins.Proteins enter the nucleus in their __________________ form. amino acid sequence Golgi apparatus sorting signal endoplasmic reticulum plasma membrane transport vesicles folded protein translocators unfolded

folded

which of the following statements about RNA splicing is false

for a gene to function properly, every exon must be removed from the primary transcript in the same fashion on every mRNA molecule produced from the same gene

indicate whether the following is true for meiosis, mitosis, both, or neither

formation of a bivalent: meiosis genetically identical products: mitosis condensation of chromosomes: both segregation of all paternal chromosomes to one cell: neither

dna base pairs

g-c (3 bonds) a-t (2 bonds) g & a have two rings, c & t have one

The N-terminal tail of histone H3 can be extensively modified, and depending on the number, location, and combination of these modifications, these changes may promote the formation of heterochromatin. What is the result of heterochromatin formation?

gene silencing

the complete set of information found in a given organism's DNA is called its ____________.

genome

the number of different types of receptors is ______ than the number of extracellular signals that act on them

greater

Several experiments were required to demonstrate how traits are inherited. Which scientist or team of scientists first demonstrated that cells contain some component that can be transferred to a new population of cells and permanently cause changes in the new cells?

griffith

The Figure clearly depicts the nucleolus, a nuclear structure that looks like a large, dark region when stained. The other dark, speckled regions in this image are the locations of particularly compact chromosomal segments called ____________.

heterochromatin

16-37 When adrenaline binds to adrenergic receptors on the surface of a muscle cell, it activates a G protein, initiating an intracellular signaling pathway in which the activated α subunit activates adenylyl cyclase, thereby increasing cAMP levels in the cell. The cAMP molecules then activate a cAMP-dependent kinase (PKA) that, in turn, activates enzymes that result in the breakdown of muscle glycogen, thus lowering glycogen levels. You obtain muscle cells that are defective in various components of the signaling pathway. Referring to Figure Q16-36, indicate how glycogen levels would be affected in the presence of adrenaline in the following cells. Would they be higher or lower than in normal cells treated with adrenaline? A. cells that lack adenylyl cyclase B. cells that lack the GPCR C. cells that lack cAMP phosphodiesterase D. cells that have an α subunit that cannot hydrolyze GTP but can interact properly with the β and γ subunits

higher higher lower lower

Both DNA and RNA are synthesized by covalently linking a nucleoside triphosphate to the previous nucleotide, constantly adding to a growing chain. In the case of DNA, the new strand becomes part of a stable helix. The two strands are complementary in sequence and antiparallel in directionality. What is the principal force that holds these two strands together?

hydrogen bonds

Although all protein structures are unique, there are common structural building blocks that are referred to as regular secondary structures. Some proteins have α helices, some have β sheets, and still others have a combination of both. What makes it possible for proteins to have these common structural elements?

hydrogen bonds along the protein backbone

Lysozyme is an enzyme that specifically recognizes bacterial polysaccharides, which renders it an effective antibacterial agent. Into what classification of enzymes does lysozyme fall?

hydrolase

Two or three α helices can sometimes wrap around each other to form coiled-coils. The stable wrapping of one helix around another is typically driven by ________________ interactions.

hydrophobic

For the polypeptide sequence listed, choose from the options given below to indicate which secondary structure the sequence is most likely to form upon folding. The nonpolar amino acids are not capitalized. Leu-Gly-Val-Leu-SER-Leu-Phe-SER-Gly-Leu-Met-Trp-Phe-Phe-Trp-Ile

hydrophobic alpha helix

Which of the following is not a chemical modification commonly found on core histone N-terminal tails?

hydroxylation

reactions that do not involve changes in gene transcription or new protein synthesis occur where?

in the cytosol

A pregnant mouse is exposed to high levels of a chemical. Many of the mice in her litter are deformed, but when they are interbred with each other, all their offspring are normal. Which of the following statements could explain these results? Note: Somatic cells are all the cells in the body except the sperm and egg. Sperm and egg are referred to as germ-line cells

in the deformed mice, somatic cells but not germ cells were mutated

18-46 Before mitosis, the number of centrosomes must [increase/decrease]. At the beginning of [anaphase/prophase] in animal cells, the centrosomes separate in a process driven partly by interactions between the [plus/minus] ends of microtubules arising from the two centrosomes. Centrosome separation initiates the assembly of the bipolar mitotic spindle and is associated with a sudden [increase/decrease] in the dynamic instability of microtubules.

increase prophase plus increase

Proteins bind selectively to small-molecule targets called ligands. The selection of one ligand out of a mixture of possible ligands depends on the number of weak, noncovalent interactions in the protein's ligand-binding site. Where is the binding site typically located in the protein structure?

inside a cavity in the protein surface

foreign substances like nicotine, morphine, and methanol exert their initial effects by...

interacting with cell surface receptors causing the receptors to transduce signal inappropriately in the absence of the normal stimulus

The segments of primary RNA that are cleaved off by spliceosomes are called _________________.

introns

Combinatorial control of gene expression __________________________.

involves groups of transcriptional regulators working together to determine the expression of a gene

when atoms are held together by ____, they are typically referred to as ____

ionic interactions, salts

A poison added to an in vitro translation mixture containing mRNA molecules with the sequence 5′-AUGAAAAAAAAAAAAUAA-3′ has the following effect: the only product made is a Met-Lys dipeptide that remains attached to the ribosome. What is the most likely way in which the poison acts to inhibit protein synthesis?

it inhibits movement of the small subunit relative to the large subunit

RNA in cells differs from DNA in that

it is single-stranded and can fold up into a variety of structures

RNA in cells differs from DNA in that ___________________.

it is single-stranded and can fold up into a variety of structures

it will be more likely to generate mismatched base pairs

The enzyme responsible for transfer of a phosphoryl group from a high energy donor to a suitable substrate is known as a:

kinase

18-46 In comparison with an interphase microtubule array, a mitotic aster contains a [smaller/larger] number of [longer/shorter] microtubules. Extracts from M-phase cells exhibit [increased/decreased/unchanged] rates of microtubule polymerization and increased frequencies of microtubule [shrinkage/growth].

larger shorter unchanged shrinkage

Given the generic signaling pathway in the figure below, match the number corresponding to the item next to the descriptor below.

ligand binds to receptor protein which causes intracellular signaling proteins to lead to effector proteins

Ca+ can trigger biological effects in cells because an unstimulated cell has an extremely --------concentration of free Ca+ in the cystosol, compared with its concentration in the ----------space in the --------creating a steep elctrochemical gradient. when Ca+ enters the cystosol, it interacts with Ca+ responsive such as ------which also binds to diacylglcerol and --------which activates CAM kinases

low extracellular ER PKC calmodulin

16-44Ca2+ can trigger biological effects in cells because an unstimulated cell has an extremely __________________ concentration of free Ca2+ in the cytosol, compared with its concentration in the __________________ space and in the __________________, creating a steep electrochemical gradient

low; extracellular; endoplasmic reticulum

Which amino acid would you expect a tRNA with the anticodon 5′-CUU-3′ to carry?

lysine

15-5 For each of the following sentences, fill in the blanks with the best word or phrase selected from the list below. Not all words or phrases will be used; use each word or phrase only once. on their way to the The *cytosol*makes up about half of the total cell volume of a typical eukaryotic cell. Ingested materials within the cell will pass through a series of compartments called *endosomes* on their way to the__________________, which contains digestive enzymes and will ultimately degrade the particles and macromolecules taken into the cell and will also degrade worn-out organelles. cytosol Golgi apparatus nucleus endoplasmic reticulum lysosome peroxisomes endosomes mitochondria plasma membrane

lysosome

18-18 Studies with Xenopus eggs identified a partly purified activity called __________________ that drives a resting Xenopus oocyte into M phase. MPF activity was found to __________________ during the cell cycle, although the amount of its kinase component, called __________________, remained constant.

maturation promoting factor oscillate Cdk

. Proteins that link the distantly bound transcription regulators to RNA polymerase and the general transcription factors include the large complex of proteins called the__________________.

mediator

________ is not involved in post-transcriptional control?

mediator

which of the following statements most correctly describes meiosis

meiosis involves a single round of DNA replication followed by two successive cell divisions

Cholesterol serves several essential functions in mammalian cells. Which of the following is not influenced by cholesterol?

membrane thickness

The _______________ is directly responsible for segregation of chromosomes into daughter cell during cell division.

microtubules

be able to identify microtubules, intermediate filaments, and actin

microtubules look like spider, intermediate filaments look like lots of wires everywhere, actin is on outer edge of square

18-71 . One class of signal molecules, called __________________, stimulates cell division by releasing the molecular brakes that keep cells in the __________________ or __________________ phase of the cell cycle. Members of a second class of signal molecules are called __________________, because they stimulate cell growth and an increase in cell mass.

mitogens G0 G1 growth factors

18-32 During M phase, the nucleus divides in a process called __________________, and the cytoplasm splits in two in a process called __________________.

mitosis cytokinesis

difference between necrosis and apoptosis

necrosis is accidental apoptosis is controlled

16-28 Indicate by writing "yes" or "no" whether amplification of a signal could occur at the particular steps described below. Explain your answers. A. An extracellular signaling molecule binds and activates a GPCR. B. The activated GPCRs cause Gα to separate from Gβ and Gγ. C. Adenylyl cyclase produces cyclic AMP. D. cAMP activates protein kinase A. E. Protein kinase A phosphorylates target proteins.

no yes yes no yes

the ___ ___ is made up if two concentric membranes and is continuous with the membrane of the endoplasmic reticulum

nuclear envelope

Which of the following methods is not used by cells to regulate the amount of a protein in the cell?

nuclear pore complexes can regulate the speed at which newly synthesized proteins are exported from the nucleus into the cytoplasm

. Transcription is similar to DNA replication in that ___________________.

nucleotide polymerization occurs only in the 5′-to-3′ direction

where do the following processes occur: transcription translation RNA splicing polyadenylation RNA capping

nucleus endoplasmic reticulum nucleus nucleus nucleus

GTPase-activating proteins (GAPs) stimulate the hydrolysis of GTP to GDP. does it switch on or off?

off

Kinesins and dyneins ____________________.

often move in opposite directions to each other

The endothelial cells found closest to the site of an infection express proteins called lectins. Each lectin binds to a particular ____________ that is presented on the surface of a target cell.

oligosaccharide

the endothelial cells found closest to the site of an infection express proteins called lectins. Each lectin binds to a particular ____________ that is presented on the surface of a target cell.

oligosaccharide

guanine nucleotide exchange factors (GEFs) promote the exchange of GDP to GTP. does it switch on or off?

Many bacterial promoters contain a region known as an __________________, to which a specific transcription regulator binds.

operator

16-2 During __________________ signaling, the signal remains in the neighborhood of the secreting cell and thus acts as a local mediator on nearby cells. Finally, __________________ signaling involves the conversion of electrical impulses into a chemical signal. Cells receive signals through a __________________, which can be an integral membrane protein or can reside inside the cell.

paracrine; neuronal; receptor

___ are fairly small organelles that provide a safe place within the cell to carry out certain biochemical reactions that generate harmful, highly reactive oxygen species. these chemicals are both generated and broken down in the same location

peroxisomes

15-60 For each of the following sentences, fill in the blanks with the best word or phrase selected from the list below. Not all words or phrases will be used; each word or phrase should be used only once. Eukaryotic cells are continually taking up materials from the extracellular space by the process of endocytosis. One type of endocytosis is *pinocytosis*, which uses *clathrin* proteins to form small vesicles containing fluids and molecules. After these vesicles have pinched off from the plasma membrane, they will fuse with the *endosome*where materials that are taken into the vesicle are sorted. A second type of endocytosis is __________________, chaperone Golgi apparatus pseudopods cholesterol mycobacterium rough ER clathrin phagocytosis SNARE endosome pinocytosis transcytosis

phagocytosis

at the start of the pathway both the a subunit and by subunit of the G protein Gq are involved in activating __________. two smaller messenger molecules __and ___ are produced. when a membrane ______ is hydrolyzed by activated phospholipase c, inositol 1,4,5-triphopsphate (IP3) diffuses through the cytosol the triggers the release of _____ from the ER by binding to and opening special _____ channels in the ER membrane. the large electrochemical gradient for ____ across this membrane causes ____ to rush out of the ER and into the cytosol. ______ remains in the plasma membrane and, together with Ca2+, helps activate the enzyme ____ which is recruited from the cytosol to the cytosolic face of the plasma membrane. _____ then phosphorylates its own set of intracellular proteins, further propagating the signal

phospholipase c IP3 DAG inositol phospholipase Ca++ Ca++ Ca++ Ca++ DAG PKC PKC

At the start of the pathway both alpha subunit and the beta(y) subunit of the G-PROTEIN (Gq) are invovled in activating --------. two small messenger molecules ------and --------are produced. when a membrane ----------is hydrolyzed by activated phospholipase C, inistol 1,4,5-triphosphate (IP3) diffucses through the cystol and triggers the release of ------from the ER BY THE BINDING TO AND OPENING ------CHANNELS IN THE ER MEMBRANE. ----------then phosphorylates its own set of intracellular proteins further propagating the signal

phospholipase c IP3 and DAG inositol phospholipid Ca+ ion Ca+ PKC

The variety and arrangement of chemical groups on monomer subunits contribute to the conformation, reactivity, and surface of the macromolecule into which they become incorporated. What type of chemical group is circled on the nucleotide shown in the figure?

phosphoryl

pinocytosis

Indicate whether the following molecules are found in plants, animals, or both. Cell wall

plants

Indicate whether the following molecules are found in plants, animals, or both. Cellulose

plants

The drug colchicine ______________________.

prevents microtubule formation.

Homologous recombination is an important mechanism in which organisms use a "backup" copy of the DNA as a template to fix double-strand breaks without loss of genetic information. Which of the following is not necessary for homologous recombination to occur?

primase

the action of CA+ in a second messenger scheme -------

produces sustained responses by controlling the flow of Ca+ into the cell

when a terminally differentiated cell in an adult body dies, it can typically be replaced in the body by a stock of

proliferating precursor cells

18-71 The survival, __________________, and size of each cell in an animal are controlled by extracellular signal molecules secreted by neighboring and distant cells. Many of these signal molecules bind to a cell-surface __________________ and trigger various intracellular signaling pathways.

proliferation receptor

be able to identify the different stages in mitosis

prophase, nucleus intact, prometaphase, chromosomes start to line up at center, anaphase, proteins get pulled apart, telophase, two cells start to form

cyclic amp exerts its effects in animals cells mainly by activating the enzyme ------- which catalyzes the transfer of the terminal phospahate group from the ATP to specific serines or threonines of selected proteins

protein kinase

16-44 When Ca2+ enters the cytosol, it interacts with Ca2+-responsive proteins such as __________________, which also binds diacylglycerol, and __________________, which activates CaM-kinases.

protein kinase Cl calmodulin

15-9 For each of the following sentences, fill in the blanks with the best word or phrase selected from the list below. Not all words or phrases will be used; use each word or phrase only once. Plasma membrane proteins are inserted into the membrane in the *endoplasmic reitculum*. The address information for protein sorting in a eukaryotic cell is contained in the *amino acid sequence* of the proteins. Proteins enter the nucleus in their *folded* form. Proteins that remain in the cytosol do not contain a *sorting signal*. Proteins are transported into the Golgi apparatus via *transport vesicles*The proteins transported into the endoplasmic reticulum by __________________ amino acid sequence Golgi apparatus sorting signal endoplasmic reticulum plasma membrane transport vesicles folded protein translocators unfolded

protein translocators

what type of macromolecule helps package DNA in eukaryotic chromosomes

proteins

which subatomic particles contribute to the atomic mass for any given element

protons and neutrons

15-60 For each of the following sentences, fill in the blanks with the best word or phrase selected from the list below. Not all words or phrases will be used; each word or phrase should be used only once. Eukaryotic cells are continually taking up materials from the extracellular space by the process of endocytosis. One type of endocytosis is *pinocytosis*, which uses *clathrin* proteins to form small vesicles containing fluids and molecules. After these vesicles have pinched off from the plasma membrane, they will fuse with the *endosome*where materials that are taken into the vesicle are sorted. A second type of endocytosis is *phagocytosis*, which is used to take up large vesicles that can contain microorganisms and cellular debris. Macrophages are especially suited for this process, as they extend __________________ (sheetlike projections of their plasma membrane) to surround the invading microorganisms. chaperone Golgi apparatus pseudopods cholesterol mycobacterium rough ER clathrin phagocytosis SNARE endosome pinocytosis transcytosis

pseudopods

In a double stranded DNA helix, ________________________.

purines base pair with pyrimidines

Which of the following statements is true?

rRNA contains the catalytic activity that joins amino acids together.

16-19 An extracellular signal molecule can act to change a cell's behavior by acting through cell-surface __________________ that control intracellular signaling proteins. These intracellular signaling proteins ultimately change the activity of __________________ proteins that bring about cell responses.

receptors; effector

The sigma subunit of bacterial RNA polymerase ___________________.

recognizes promoter sites in the DNA

the sigma subunit of bacterial RNA polymerase

recognizes promoter sites in the DNA

18-46 The changes in microtubule dynamics are largely due to [enhanced/reduced] activity of microtubule-associated proteins and [increased/decreased] activity of catastrophins. The new balance between polymerization and depolymerization of microtubules is necessary for the mitotic spindle to move the [replicated chromosomes/daughter chromosomes] to the metaphase plate.

reduced increased replicated chromosomes

which of the following statements about prokaryotic mRNA molecules is false

ribosomes must bind to the 5' cap before initiating translation

Which of the following items below are not important for flagellar movement?

sarcoplasmic reticulum

in eukaryotes but not in prokaryotes, ribosomes find the start site of translation by ____

scanning along the mRNA from the 5' end

. In eucaryotes, but NOT in procaryotes, ribosomes find the start site of translation by ____________________________.

scanning along the mRNA from the 5′ end

15-37 For each of the following sentences, fill in the blanks with the best word or phrase selected from the list below. Not all words or phrases will be used; use each word or phrase only once. Proteins are transported out of a cell via the __________________ carbohydrate Golgi apparatus disulfide bonds hydrogen bonds endocytic ionic bonds endomembrane lysosome endoplasmic reticulum protein endosome secretory exocytic

secretory

. DNA replication is accomplished by employing a ________________ mechanism.

semiconservative

Oligosaccharides are short sugar polymers that can become covalently linked to proteins and lipids through condensation reactions. These modified proteins and lipids are called glycoproteins and glycolipids, respectively. Within a protein, which of the amino acids (shown in Figure 1) is the most probable target for this type of modification?

serine

16-27 G-protein-coupled receptors (GPCRs) all have a similar structure with __________________ transmembrane domains. When a GPCR binds an extracellular signal, an intracellular G protein, composed of __________________ subunits, becomes activated.

seven; three

Which of the following chemical groups is not used to construct a DNA molecule?

six-carbon sugar

DNA polymerases are processive, which means that they remain tightly associated with the template strand while moving rapidly and adding nucleotides to the growing daughter strand. Which piece of the replication machinery accounts for this characteristic?

sliding clamp

reactions that invovle gene expression occur------

slowly

The _________ subunit of a ribosome is the first to interact with new mRNAs.

small

Elevation of intracellular inositol trisphosphate (IP3) results in a release of Ca2+ from what organelle?

smooth ER

__________________ molecules are important in the splicing of RNA transcripts

snRNA

15-9 For each of the following sentences, fill in the blanks with the best word or phrase selected from the list below. Not all words or phrases will be used; use each word or phrase only once. Plasma membrane proteins are inserted into the membrane in the *endoplasmic reitculum*. The address information for protein sorting in a eukaryotic cell is contained in the *amino acid sequence* of the proteins. Proteins enter the nucleus in their *folded* form. Proteins that remain in the cytosol do not contain a __________________. amino acid sequence Golgi apparatus sorting signal endoplasmic reticulum plasma membrane transport vesicles folded protein translocators unfolded

sorting signal.

Macromolecules in the cell can often interact transiently as a result of noncovalent interactions. These weak interactions also produce stable, highly specific interactions between molecules. Which of the factors below is the most significant in determining whether the interaction will be transient or stable?

surface complementarity between molecules

18-71 The third class of signal molecules, called __________________, inhibits __________________ by regulating members of the __________________ family of proteins. In addition to such stimulatory factors, some signal proteins such as __________________ act negatively on other cells, inhibiting their survival, growth, or proliferation.

survival factors apoptosis Bc12 myostatin

The process of DNA replication requires that each of the parental DNA strands be used as a ___________________ to produce a duplicate of the opposing strand.

template

an individual that arises by reproductive cloning has a nuclear genome that is identical to

the adult who donated the cell for nuclear transplantation

the ribosome is important for catalyzing the formation of peptide bonds. which of the following statements is true?

the catalytic site for peptide bond formation is formed primarily from an rRNA

What would be the most obvious outcome of repeated cell cycles consisting of S phase and M phase only?

the cells produced would get smaller and smaller

A group of membrane proteins can be extracted from membranes only by using detergents. All the proteins in this group have a similar amino acid sequence at their C-terminus: -KKKKKXXC (where K stands for lysine, X stands for any amino acid, and C stands for cysteine). This sequence is essential for their attachment to the membrane. What is the most likely way in which the C-terminal sequence attaches these proteins to the membrane?

the cysteine residue is covalently attached to a membrane lipid

The concentration of a particular protein X in a normal human cell rises gradually from a low point, immediately after cell division, to a high point, just before cell division, and then drops sharply. The level of its mRNA in the cell remains fairly constant throughout this time. Protein X is required for cell growth and survival, but the drop in its level just before cell division is essential for division to proceed. You have isolated a line of human cells that grow in size in culture but cannot divide, and on analyzing these mutants, you find that levels of X mRNA in the mutant cells are normal. Which of the following mutations in the gene for X could explain these results?

the deletion of a sequence that encodes sites at which ubiquitin can be attached to the protein

which of the following statements about the genetic code is correct

the genetic code is redundant

Okazaki fragments are used to elongate

the lagging strand away from the replication fork

telomeres serve as caps at the ends of linear chromosomes. which of the following is not true regarding the replication of telomeric sequences?

the leading strand doubles back on itself to form a primer for the lagging strand

Which of the following phenomena will be observed if a cell's membrane is pierced?

the membrane reseals

Which of the following events does not usually occur during interphase?

the nuclear envelope breaks down

a stem cell divides into two daughter cells. one of the daughter cells goes on to become a terminally differentiated cell. what is the typical fate of the other daughter cell

the other daughter cell typically remains a stem cell

Initiator proteins bind to replication origins and disrupt hydrogen bonds between the two DNA strands being copied. Which of the factors below does not contribute to the relative ease of strand separation by initiator proteins?

the reaction can occur at room temperature

nonhomologous end joining can result in all but which of the following?

the recovery of lost nucleotides on a damaged DNA strand

which of the following does not occur before a eukaryotic mRNA is exported from the nucleus

the ribosome binds to the mRNA

The correct folding of proteins is necessary to maintain healthy cells and tissues. Misfolded proteins are responsible for such neurodegenerative disorders as Alzheimer's disease, Huntington's disease, and Creutzfeldt-Jakob disease (the specific faulty protein is different for each disease). What is the ultimate fate of these disease-causing, misfolded proteins?

they form protein aggregates

some very rare individuals are genetically male but lack the testosterone receptor. what happens in individuals who lack the receptor for the male sex hormone testosterone?

they make testosterone but their cell cannot respond to it. as a result, these individuals develop as females

All of the following are true about heterotrimeric G proteins EXCEPT: - A. They bind either GDP or GTP. - B. They have GTPase activity. - C. They act as binary (on-off) switches. - D. They help amplify a hormone's signal. - E. They phosphorylate proteins.

they phosphorylate proteins

molecular chaperones can work by creating an "isolation chamber" what is the purpose of this chamber?

this chamber serves to protect unfolded proteins from interacting with other proteins in the cytosol, until the protein folding is completed

The DNA duplex consists of two long covalent polymers wrapped around each other many times over their entire length. The separation of the DNA strands for replication causes the strands to be "overwound" in front of the replication fork. How does the cell relieve the torsional stress created along the DNA duplex during replication?

topoisomerases break the covalent bonds of the backbone allowing the local unwinding of DNA ahead of the replication fork

the artificial introduction of three key ____ into an adult cell can convert the adult cell into a cell with the properties of ES cells

transcription factors

15-9 For each of the following sentences, fill in the blanks with the best word or phrase selected from the list below. Not all words or phrases will be used; use each word or phrase only once. Plasma membrane proteins are inserted into the membrane in the *endoplasmic reitculum*. The address information for protein sorting in a eukaryotic cell is contained in the *amino acid sequence* of the proteins. Proteins enter the nucleus in their *folded* form. Proteins that remain in the cytosol do not contain a *sorting signal* Proteins are transported into the Golgi apparatus via __________________. amino acid sequence Golgi apparatus sorting signal endoplasmic reticulum plasma membrane transport vesicles folded protein translocators unfolded

transport vesicles.

18-51 Is the following statement true or false? After the nuclear envelope breaks down, microtubules gain access to the chromosomes and, every so often, a randomly probing microtubule captures a chromosome and ultimately connects to the kinetochore to become a kinetochore microtubule of the spindle.

true

G-proteins and monomeric GTPase are active when GTP is bound but inactive when GDP is bound (true or false)

true

Glycolipids lack the glycerol component found in phospholipids.

true

a protein that relies on protein-protein interactions to stabilize its membrane association is classified as a peripheral membrane protein because it can be dissociated without the use of detergents.

true

18-7 Are the statements below true or false? Explain your answer. A. Statement 1: Generally, in a given organism, the S, G2, and M phases of the cell cycle take a defined and stereotyped amount of time in most cells. B. Statement 2: Therefore, the cell-cycle control system operates primarily by a timing mechanism, in which the entry into one phase starts a timer set for sufficient time to complete the required tasks. After a given amount of time has elapsed, a molecular "alarm" triggers movement to the next phase.

true false

GPCRs mediate responses to an enormous diversity of extracellular signal molecules and are involved in a large variety of cell process (true or false)

true (they are attractive target for the development of drugs to treat many disorders)

16-27 __________________ of the G-protein subunits are tethered to the plasma membrane by short lipid tails. When unstimulated, the α subunit is bound to __________________, which is exchanged for __________________ on stimulation.

two; GDP; GTP

15-9 For each of the following sentences, fill in the blanks with the best word or phrase selected from the list below. Not all words or phrases will be used; use each word or phrase only once. Plasma membrane proteins are inserted into the membrane in the *endoplasmic reitculum*. The address information for protein sorting in a eukaryotic cell is contained in the *amino acid sequence* of the proteins. Proteins enter the nucleus in their *folded* form. Proteins that remain in the cytosol do not contain a *sorting signal*. Proteins are transported into the Golgi apparatus via *transport vesicles* The proteins transported into the endoplasmic reticulum by *protein translocators* are in their __________________ form. amino acid sequence Golgi apparatus sorting signal endoplasmic reticulum plasma membrane transport vesicles folded protein translocators unfolded

unfolded

In principle, _________ cell types can an organism having three different types of transcription regulator and thousands of genes create?

up to 8

Membranes undergo spontaneous rearrangement if torn. Which of the following would happen if a cell membrane had a large tear?

vesicles form

The figure shows the pathway through which nitric oxide (NO) triggers smooth muscle relaxation in a blood-vessel wall. Which of the following situations would lead to relaxation of the smooth muscle cells in the absence of acetylcholine?

• (b) a muscle cell that has a defect in guanylyl cyclase such that it constitutively converts GTP to cyclic GMP

Which of the following is not a general mechanism of cell memory? • (a) a positive feedback loop, mediated by a transcriptional regulator that activates transcription of its own gene in addition to other cell-type specific genes • (b) inheritance of histone modification patterns when cells divide • (c) proper segregation of housekeeping proteins when cells divide • (d) inheritance of DNA methylation patterns when cells divide

• (c) proper segregation of housekeeping proteins when cells divide

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