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BIOL 3510 Final

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Place the following in order of size, from the smallest to the largest. (1 = smallest, 5 = largest) protofilament microtubule α-tubulin tubulin dimer mitotic spindle

1. a-tubulin 2. tubulin dimer 3. protofilament 4. microtubule 5. mitotic spindle

Tubulin dimers are stacked together into protofilaments;__________________ parallel protofilaments form the tubelike structure of amicrotubule.

Match the type of intermediate filament with its appropriate location. 1) lamins 2) neurofilaments 3) vimentins 4)keratins A. nerve cells B. epithelia C. nucleus D. connective tissue

1C, 2A, 3D, 4B

The following proteins are important for cell movement. Match the following proteins with their function. 1) myosin 2) ARP proteins 3) profilin 4) integrins 5) formins A) nucleation of new actin filaments at the side of an existing filament B) regulation of the availability of actin monomers C) important for the growth of straight, unbranched actin filaments D) contracting the rear of the cell E) involvement in focal contacts

1D, 2A, 3B, 4E, 5C

Match the components involved with ER transport with the appropriate cellular location. a. cytosol b. ER lumen c. ER membrane 1. signal-recognition particle 2. protein translocator 3. mRNA 4. SRP receptor 5. active site of signal peptidase

1a, 2c, 3a, 4c, 5b

Arrange the two following lists to give the most appropriate pairings. 1. Endocytic vesicle 2. Fusion of endocytic vesicles 3. Lysosomal enzyme transport vesicles and late endosomes 4. Lysosomal enzymes a. Clathrin coated pits b. Lysosomes c. Early endosomes d. Mannose 6-phosphate residues

1a, 2c, 3b, 4d

Name the membrane-enclosed compartments in a eucaryotic cell where each of the functions listed below takes place: 1. photosynthesis 2. transcription 3. oxidative phosphorylation 4. modification of secreted proteins 5. steroid hormone synthesis 6. degradation of worn-out organelles 7. new membrane synthesis 8. breakdown of lipids and toxic molecules a. chloroplast b. Golgi apparatus and rough ER c. mitochondrion d. peroxisome e. lysosome f. nucleus g. smooth ER

1a, 2f, 3c, 4g, 5g, 6e, 7b, 8d

Match the target of the G protein with the appropriate signaling outcome. 1. adenylyl cyclase 2. ion channels 3. phospholipase C A. cleavage of inositol phospholipids b. increase in cAMP levels c. changes in membrane potential

1b, 2c, 3a

Arrange the two following lists to give the most appropriate pairings. 1. Cis Golgi network 2. Trans Golgi network 3. Constitutive secretory pathways 4. Regulated secretory pathways a. Allows proteins to be synthesized and secreted during discontinuous, discrete secretory events b. Allows proteins to be synthesized and secreted continously c. Packages materials for secretion into appropriate types of vesicles d. Coatomer coated I vesicles

1d, 2c, 3b, 4a

Rank the following cytoskeletal filaments from smallest to largest in diameter. (1= smallest in diameter, 4 = largest) ______ intermediate filaments ______ microtubules ______ actin filament ______ myofibril

2, 3, 1, 4

In the budding yeast, activation of the GTP-binding protein Cdc42 occurs on binding of an external signal (pheromone) to a G-protein-coupled receptor. Activation of Cdc42 promotes actin polymerization. Predict what would happen to actin polymerization, in comparison with pheromone-treated cells, in the following cases. A. You add pheromone to an inhibitor of G-protein-coupled receptors. B. You add pheromone to a nonhydrolyzable analog of GTP.

A. Less actin polymerization B. More actin polymerization

Microtubules are formed from the tubulin heterodimer, which is composed of the nucleotide-binding ___A___ protein and the ___B___ protein. Tubulin dimers are stacked together into protofilaments; ___C___ parallel protofilaments form the tubelike structure of a microtubule. ___D___ rings are important for microtubule nucleation and are found in the ___E___, which is usually found near the cell's nucleus in cells that are not undergoing mitosis. A microtubule that is quickly growing will have a ___F___ cap that helps prevent the loss of subunits from its growing end. Stable microtubules are used in cilia and flagella; these microtubules are nucleated from a ___G___ and involve a "___H___ plus two" array of microtubules. The motor protein ___I___ generates the bending motion in cilia; the lack of this protein can cause Kartagener's syndrome in humans.

A: beta-tubulin B: alpha-tubulin C: thirteen D: gamma-tubulin E: centrosome F: GTP G: basal body H: nine I: dynein

Intermediate filaments are found mainly in cells that are subject to mechanical stress. Mutations in genes that disrupt intermediate filaments cause some rare human diseases. For example, the skin of people with epidermolysis bullosa simplex is very susceptible to mechanical injury; people with this disorder have mutations in their ___A___ genes, the intermediate filament found in epithelial cells. These filaments are usually connected from cell to cell through junctions called ___B___s. The main filaments found in muscle cells belong to the ___C___ family; people with disruptions in these intermediate filaments can have muscular dystrophy. In the nervous system, ___D___s help strengthen the extremely long extensions often present in nerve cell axons; disruptions in these intermediate filaments can lead to neurodegeneration. People who carry mutations in the gene for ___E___, an important protein for cross-linking intermediate filaments, have a disease that combines symptoms of epidermolysis bullosa simplex, muscular dystrophy, and neurodegeneration.

A: keratin B: desmosome C: vimentin D: neurofilaments E: plectin

There are many actin-binding proteins in cells that can bind to actin and modify its activity. Some proteins such as ___A___ bind to actin monomers, sequestering them until needed for filament formation. ___B___ proteins bind to the end of actin filaments. The ___C___ proteins are important for nucleation of the branched actin structures commonly found in the ___D___ of moving cells, whereas ___E___ are important for the formation of unbranched actin filaments commonly found in ___F___ Proteins belonging to the ___G___ family of GTPases regulate changes in the actin cytoskeleton in response to extracellular signals.

A: thymosin B: capping C: ARP D: lamellipodia E: formin F: filipodia G: Rho

Action potentials are usually mediated by voltage-gated Ca2+ channels. (T/F)

Active insulin is a dimer, which is produced as an inactive polypeptide by two specific enzyme-catalyzed hydrolytic reactions. (T/F)

Aquaporin channels are found in the plasma membrane, allowing the rapid passage of water molecules and small ions in and out of cells. (T/F)

Both the Na+/glucose symporter and Na+/K+-adenosine triphosphatase of enterocytes use free energy from the hydrolysis of ATP to drive the transmembrane transport of their respective solutes. (T/F)

Covalent bonds backed with protein monomers hold together cytoskeletal filaments. (T/F)

Enzymes bind to, and chemically alter, substrate molecules. (T/F)

Facilitated diffusion can be described as the favorable movement of one solute down its concentration gradient being coupled with the unfavorable movement of a second solute up its concentration gradient. (T/F)

Gap junctions are large pores that connect the cytosol to the extracellular space. (T/F)

Hemidesmosomes and desmosomes are both connected to microfilaments called tonofilaments. (T/F)

Lysosomes were discovered by de Duve and co-workers following leakage of alkaline phosphatase activity on prolonged storage of animal tissue homogenates in the cold. (T/F)

Minus end-directed microtubule motors (like dyneins) deliver their cargo to the periphery of the cell, whereas plus end-directed microtubule motors (like kinesins) deliver their cargo to the interior of the cell. (T/F)

Most organelles of a neuron are distributed throughout the cytoplasm. (T/F)

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

The differences in permeability between artificial lipid bilayers and cell membranes arise from variations in phospholipid content. (T/F)

The ion selectivity of a channel completely depends solely on the charge of the amino acids lining the pore inside the channel. (T/F)

The net negative charge on the cytosolic side of the membrane enhances the rate of glucose import into the cell by a uniporter. (T/F)

Transporters are similar to channels, except that they are larger, allowing folded proteins as well as smaller organic molecules to pass through them. (T/F)

Voltage-gated K+ channels also open immediately in response to local depolarization, reducing the magnitude of the action potential. (T/F)

A microtubule that is quickly growing will have a __________________ cap that helps prevent the loss of subunits from its growing end.

GTP

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?

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

Cells expend energy in the form of ATP hydrolysis so as to maintain ion concentrations that differ from those found outside the cell. (T/F)

Globular proteins fold up into compact, spherical structures that have uneven surfaces. They tend to form multi-subunit complexes, which also have a rounded shape. (T/F)

Most ion channels are gated, which allow them to open and close in response to a specific stimulus rather than allowing the constant, unregulated flow of ions. (T/F)

Neurotransmitters are small molecules released into the synaptic cleft after the fusion of synaptic vesicles with the presynaptic membrane. (T/F)

One type of endocytosis is pinocytosis, which uses clathrin proteins to form small vesicles containing fluids and molecules. (T/F)

Phagocytic cells extend pseudopods that surround the material to be ingested. (T/F)

Phagocytic cells scavenge dead and damaged cells and cell debris (T/F)

Serine, threonine and tyrosine residues are all subjected to phosphorylation in various signal transduction pathways. (T/F)

The centrosome relies on microtubule assembly and disassembly to locate chromosomes in the cytoplasm. (T/F)

The cytoskeleton controls the location of organelles in eukaryotic cells. (T/F)

The electrochemical gradient for K+ across the plasma membrane is small. Therefore, any movement of K+ from the inside to the outside of the cell is driven solely by its concentration gradient. (T/F)

Transducin is a typical trimeric G protein. (T/F)

Transporters undergo transitions between different conformations, depending on whether the substrate-binding pocket is empty or occupied. (T/F)

Voltage-gated Na+ channels become automatically inactivated shortly after opening, which ensures that the action potential cannot move backward along the axon. (T/F)

What would happen in each of the following case: You move the N-terminal ER signal sequence to the C-terminal end of the protein. (Assume that the protein involved is a soluble protein, not a membrane protein.)

The protein will not enter the ER. Because the C-terminus of the protein is the last part to be made, the ribosomes synthesizing this protein will not be recognized by the signal-recognition particle (SRP) and hence not carried to the ER.

What would happen in each of the following case: You change the hydrophobic amino acids in an ER signal sequence into other, hydrophobic, amino acids. (Assume that the protein involved is a soluble protein, not a membrane protein.)

The protein will still be delivered into the ER. It is the distribution of hydrophobic amino acids that is important, not the actual sequence.

What would happen in each of the following case: You add a signal sequence (for the ER) to the N-terminal end of a normally cytosolic protein. (Assume that the protein involved is a soluble protein, not a membrane protein.)

This protein will now be transported into the ER lumen

A bacterium is suddenly expelled from a warm human intestine into the cold world outside. Which of the following adjustments might the bacterium make to maintain the same level of membrane fluidity? a. Produce lipids with hydrocarbon tails that are shorter and have more double bonds. b. Decrease the amount of cholesterol in the membrane. c. Produce lipids with hydrocarbon tails that are longer and have fewer double bonds d. Decrease the amount of glycolipids in the membrane.

A core nucleosomes is composed of (choose the best answer) a. two copies each of histone H2A, H2B, H3 and H4 and 147 bp of DNA. b. two copies each of histone H2A, H2B, H3 and H4 and 1470 bp of DNA. c. four copies each of histone H2A, H2B, H3 and H4 and 147 bp of DNA. d. four copies each of histone H2A, H2B, H3 and H4 and 1470 bp of DNA.

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? (a) The cysteine residue is covalently attached to a membrane lipid. (b) The peptide spans the membrane as an α helix. (c) The peptide spans the membrane as part of a β sheet. (d) The positively charged lysine residues interact with an acidic integral membraneprotein.

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 researcher made an interesting observation about a protein made by the rough endoplasmic reticulum and eventually used to build a cell's plasma membrane. The protein in the plasma membrane was actually slightly different from the protein made in the ER. The protein was probably altered in the _____. a. Golgi apparatus b. smooth endoplasmic reticulum c. plasma membrane d. transport vesicles e. rough endoplasmic reticulum

Actin-binding proteins bind to actin and can modify its properties. You purify a protein, Cap1, that seems to bind and cap one end of an actin filament, although you do not know whether it binds the plus end or the minus end. To determine which end of the actin filament your protein binds to, you decide to examine the effect of Cap1 on actin polymerization by measuring the kinetics of actin filament formation in the presence and the absence of Cap1 protein. You obtain the following results (see Figure Q17-48). Do you think Cap1 binds the plus end or the minus end of actin? a. Plus End b. Minus End

All intermediate filaments are of similar diameter because ____________. (a) the central rod domains are similar in size and amino acid sequence. (b) the globular domains are similar in size and amino acid sequence. (c) covalent bonds among tetramers allow them to pack together in a similar fashion. (d) there is only a single type of intermediate filament in every organism.

At which cell cycle checkpoint, cell cycle is halted if cell's DNA is damaged (a) G1 - S (b) S - G2 (c) G2 - M (d) G0 - G1

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. 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.

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 needs to be further modified before it is mature. b. The oligosaccharide should have been added one sugar at a time. c. The oligosaccharide needs a disulfide bond. d. The oligosaccharide should have been added to the serine instead of the asparagine.

Cells use membranes to help maintain set ranges of ion concentrations inside and outside the cell. Which of the following ions is the most abundant outside a typical mammalian cell? a. Na+ b. K+ c. Ca^2+ d. Cl-

Cholesterol serves several essential functions in mammalian cells. Which of the following is not influenced by cholesterol? Select one: a. membrane thickness b. membrane fluidity c. membrane permeability d. membrane rigidity

Compared to the normal situation, in which actin monomers carry ATP, what do you predict would happen if actin monomers that bind a nonhydrolyzable form of ATP were incorporated into actin filaments? (a) Actin filaments would grow longer. (b) Actin filaments would grow shorter because depolymerization would be enhanced. (c) Actin filaments would grow shorter because new monomers could not be added to the filaments. (d) No change, as addition of monomers binding nonhydrolyzable ATP would not affect actin filament length.

Complete the sentence with the best option provided below. The secondary structures of a protein are the a. regular, repeated folds present in a lowest energy conformation. b. temporary, unstable protein folding conformations. c. interactions between polar amino acid side chains. d. chemical modifications of amino acid side chains.

Consider the mechanism by which actin polymerize. Which of the items below does not describe something similar about the polymerization mechanisms of actin and microtubules? a. Depolymerization initiates at the plus ends of filaments. b. Although both filaments can grow from both ends, the growth rate is faster at the plus ends. c. Free subunits (actin and tubulin) carry nucleoside triphosphates. d. Nucleotide hydrolysis promotes depolymerization of filaments.

Cyanide binds with at least one molecule involved in producing ATP. If a cell is exposed to cyanide, most of the cyanide would be found within the a. mitochondria. b. ribosomes. c. peroxisomes. d. lysosomes. e. endoplasmic reticulum.

Cyclin dependent kinases which control progression through cell cycle checkpoints are totally activated by which of the following (a) Binding to cyclin, plus phosphorylation by a Cdk activating protein kinase (b) Binding to cyclins (c) Phosphorylation by Cdk activating protein kinase (d) Phosphorylation by a tyrosine kinase

During mRNA splicing, which snRNA(s) base pair with the 5' splice (donor) site next to exon 1 out of a total of 2 exons? Choose the best answer. a. U1 b. U2 c. U1 and U2 d. U2 and U6

Eukaryotic cells are able to trigger the release of material from secretory vesicles to the extracellular space using a process called exocytosis. An example of materials commonly released this way is a. hormones. b. nucleic acids. c. sugars. d. cytosolic proteins.

Figure Q15-34 shows the organization of a protein 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 the diagram which of the following statements must be true? a. The C-terminus of this protein is cytoplasmic. b. The mature version of this protein will span the membrane twice, with both the N- and C-terminus in the cytoplasm. c. None of the above. d. The N-terminus of this protein is cytoplasmic.

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 C-terminus of this protein is cytoplasmic. b. The mature version of this protein will span the membrane twice, with both the N- and C-terminus in the cytoplasm. c. The N-terminus of this protein is cytoplasmic. d. None of the above.

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 C-terminus of Krt1 will be inserted into the plasma membrane. b. When this vesicle fuses with the plasma membrane, the entire Krt1 protein will be secreted into the extracellular space. 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.

Foods are broken down into simple molecular subunits for distribution and use throughout the body. Which type of simple subunits, listed below, is used preferentially as an energy source? (a) simple sugars (b) proteins (c) free fatty acids (d) glycerol

For both actin and microtubule polymerization, nucleotide hydrolysis is important for ______. a. decreasing the binding strength between subunits on filaments. b. increasing the rate at which subunits are added to the filaments. c. promoting nucleation of filaments. d. stabilizing the filaments once they are formed.

Genes in eukaryotic cells often have intronic sequences coded for within the DNA. These sequences are ultimately not translated into proteins. Why? a. Intronic sequences are removed from RNA molecules by the spliceosome, which works in the nucleus. b. Introns are not transcribed by RNA polymerase. c. Introns are removed by catalytic RNAs in the cytoplasm. d. The ribosome will skip over intron sequences when translating RNA into protein.

Glycolysis is an anaerobic process used to catabolize glucose. What does it mean for this process to be anaerobic? a. no oxygen is required b. no oxidation occurs c. it takes place in the lysosome d. glucose is broken down by the addition of electrons

Humans produce billions of different antibodies, each with a different binding site. These antibodies recognize a target called an _______. a.antigen. b.substrate. c.enzyme. d.catalyst.

In step 4 of glycolysis, a six-carbon sugar (fructose 1,6-bisphosphate) is cleaved to produce two three-carbon molecules (dihydroxyacetone phosphate and glyceraldehyde 3-phosphate). Which enzyme catalyzes this reaction? (a) aldolase (b) phosphoglucose isomerase (c) enolase (d) triose phosphate isomerase

In step 4 of the citric acid cycle, the reduction of NAD+ to NADH is coupled to the generation of CO2 and the formation of a high-energy thioester bond. The energy of the thioester bond is harnessed in step 5. What is the energy used for? (a) to generate a molecule of GTP (b) to generate a molecule of ATP (c) to generate a proton gradient (d) to generate a molecule of NADH

In the final stage of the oxidation of food molecules, a gradient of protons is formed across the inner mitochondrial membrane, which is normally impermeable to protons. If cells were exposed to an agent that causes the membrane to become freely permeable to protons, which of the following effects would you expect to observe? (a) The ratio of ATP to ADP in the cytoplasm would fall. (b) NADH would build up. (c) Carbon dioxide production would cease. (d) The consumption of oxygen would fall.

Kinesin and dynein motor proteins each use the energy of ____ to power their movements _______ along microtubules. (a) ATP hydrolysis, in a single direction (b) ATP hydrolysis, in both directions (c) GTP hydrolysis, in a single direction (d) GTP hydrolysis, in both directions

Many receptors for neurotransmitters are _______ ion channels. a. Ligand gated b. Stress gated c. Voltage gated

Membrane lipids are capable of many different types of movement. Which of these does not occur spontaneously in biological membranes? (a) switching between lipid layers (b) lateral movement (c) rotation (d) flexing of hydrocarbon chains

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? Select one: a. anchors b. receptors c. channels d. enzymes

Membrane synthesis in the cell requires the regulation of growth for both halves of the bilayer and the selective retention of certain types of lipids on one side or the other. Which group of enzymes accomplishes both of these tasks? a. flippases b. glycosylases c. phospholipases d. convertases

Methylation and acetylation are common changes made to histone H3, and the specific combination of these changes is sometimes referred to as the "histone code." Which of the following patterns will probably lead to gene silencing? a. lysine 9 methylation b. lysine 4 methylation and lysine 9 acetylation c. lysine 14 acetylation d. lysine 9 acetylation and lysine 14 acetylation

Neurotransmitters are released into the synapse at which of the following? a) Presynaptic membrane b) Postsynaptic membrane c) Golgi apparatus d) Axon hillock

Paracrine signaling is involved in which of the following? a. Chemical signals that can only travel limited distances between cells b. Hormonal communication c. Synaptic transmission d. None of the above

Plasma membranes are extremely thin and fragile, requiring an extensive support network of fibrous proteins. This network is called the ____________. (a) cortex (b) attachment complex (c) cytoskeleton (d) spectrin

Porin proteins form large, barrel-like channels in the membrane. Which of the following is not true about these channels? (a) They are made primarily of α helices. (b) They are made primarily of β sheets. (c) They cannot form narrow channels. (d) They have alternating hydrophobic and hydrophilic amino acids.

Proto-oncogenes can be transformed to oncogenes by all of the following mechanisms except (a) Elimination of their start signals for translation (b) During a viral infection cycle (c) Chromosomal rearrangements (d) Chemically induced mutagenesise) Radiation induced mutation

Pumps are transporters that are able to harness energy provided by other components in the cells to drive the movement of solutes across the membranes, against their concentration gradient. This type of transport is called ______. a. Active transport b. Free diffusion c. Facilitated diffusion d. Passive transport

RNA in cells differs from DNA in that a. it contains the base uracil, which pairs with cytosine. b. it is single-stranded and cannot form base pairs. c. it is single-stranded and can fold up into a variety of structures. d. the sugar ribose contains fewer oxygen atoms than does deoxyribose.

Several different classes of enzymes are needed for the catabolism of carbohydrates. Which of the following descriptions best matches the function of an isomerase? (a) An enzyme that catalyzes the rearrangement of bonds within a single molecule. (b) An enzyme that catalyzes a change in the position of a specific chemical group within a single molecule. (c) An enzyme that catalyzes the oxidation of a molecule by removing a hydride ion. (d) An enzyme that catalyzes the addition of phosphate groups to other molecules

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

Specific regions of eukaryotic chromosomes contain sequence elements that are absolutely required for the proper transmission of genetic information from a mother cell to each daughter cell. These regions participate is the cell cycle and are required correct chromosomal separation. Which of the following is NOT known to be one of these required elements in eukaryotes? a. protein-coding regions b. origins of replication c. telomeres d. centromeres

The acetylcholine receptor in skeletal muscle cells is a _______ ion channel. Select one: a. Ligand gated b. Stress gated c. Voltage gated

The branch point A residue involved in lariat formation is part of the a. intron. b. exon. c. 5''UTR. d. 3'UTR.

The central dogma provides a framework for thinking about how genetic information is copied and used to produce structural and catalytic components of the cell. From the choices below, select the order of biochemical processes that best correlates with the tenets of the central dogma. a. replication, transcription, translation b. replication, translation, transcription c. translation, transcription, replication d. translation, replication, transcription

The characteristic of malignant other than a benign tumor is (a) Undergoes metastasis (b) Develops blood supply (c) Cell divides an unlimited number of times (d) Grows without needing a growth signal

The citric acid cycle is a critical sequence of reactions for energy production, which take place in the matrix of the mitochondria. The reaction cycle requires materials from the cytosol to be converted into acetyl CoA, which represents the starting point of a new cycle. Which of the following statements about acetyl CoA is true? (a) Amino acids can be converted into acetyl CoA. (b) Pyruvate is converted into acetyl CoA in the cytosol. (c) Triacylglycerol molecules are transported into the mitochondrial matrix and cleaved by lipases to produce acetyl CoA. (d) Oxaloacetate is converted directly into acetyl CoA to feed the citric acid cycle.

The citric acid cycle is a series of oxidation reactions that removes carbon atoms from substrates in the form of CO2. Where do the oxygen atoms in the carbon dioxide molecules come from? (a) water (b) phosphates (c) molecular oxygen (d) acetyl CoA

The conversion of glyceraldehyde 3-phosphate to 1,3 bisphosphoglycerate in step 6 of glycolysis generates a "high energy" phosphoanhydride bond. Which of the following best describes what happens to that bond in step 7? (a) It is hydrolyzed to drive the formation of ATP (b) It is hydrolyzed to drive the formation of NADH. (c) It is hydrolyzed to generate pyruvate. (d) It is oxidized to CO2.

The end of a growing microtubules is rich in which type of tubulin molecule? a) GTP-associated tubulin molecules b) GDP-associated tubulin molecules

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 Select one: a. oligosaccharide b. aminophospholipid c. polysaccharide d. sphingolipid

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. (a) oligosaccharide (b) aminophospholipid (c) polysaccharide (d) sphingolipid

The following statement is consistent with which type(s) of microtubule? "It is arranged in a "9 + 2" array." (a) cilliary (or flagellar) microtubule (b) mitotic spindle microtubule (c) both a and b (d) none of the above

The following statement is consistent with which type(s) of microtubule? "It is involved in moving fluid over the surface of cells." (a) cilliary (or flagellar) microtubule (b) mitotic spindle microtubule (c) both a and b (d) none of the above

The following statement is consistent with which type(s) of microtubule? "It is involved in sperm motility." (a) cilliary (or flagellar) microtubule (b) mitotic spindle microtubule (c) both a and b (d) none of the above

The following statement is consistent with which type(s) of microtubule? "The basal body is the organizing center." (a) cilliary (or flagellar) microtubule (b) mitotic spindle microtubule (c) both a and b (d) none of the above

The graph in Figure Q17-31 shows the time course of the polymerization of pure tubulin in vitro. Assume that the starting concentration of free tubulin is higher than it is in cells. Figure Q17-31 Three parts of the curve are labeled above it as A, B, and C. You conduct a similar in vitro tubulin-polymerization experiment, only you include purified centrosomes in your preparation. When you plot your data, which part of your graph should be most dissimilar to the curve shown in Figure Q17-31? (a) A (b) B (c) C (d) None. The shape of my graph should be identical to the graph produced when tubulin is polymerized in the absence of purified centrosomes

The mutation which cannot give rise to an oncogene (a) Addition or deletion of a base producing a nonsense message and an inactive protein product (b) A point mutation changing just one amino acid in protein product (c) A translocation, putting gene under control of strong promoter producing over expression (d) A point mutation producing stop codon, premature termination

The oxygen-dependent reactions required for cellular respiration were originally thought to occur in a linear pathway. By using a competitive inhibitor for one enzyme in the pathway, investigators discovered that these reactions occur in a cycle. What compound served as the inhibitor? (a) malonate (b) malate (c) fumarate (d) succinate

The plasma membrane serves many functions, many of which depend on the presence of specialized membrane proteins. Which of the following roles of the plasma membrane could still occur if the bilayer were lacking these proteins? a. selective permeability b. import/export of molecules c. intercellular communication d. cellular movement

The stimulation of a motor neuron ultimately results in the release of a neurotransmitter at the synapse between the neuron and a muscle cell. What type of neurotransmitter is used at these neuromuscular junctions? Select one: a. acetylcholine b. glutamate c. GABA d. glycine

Transporters, in contrast to channels, work by ______. a. Specific binding to solutes b. A gating mechanism c. Filtering solutes by charge d. Filtering solutes by size

Voltage-gated channels contain charged protein domains, which are sensitive to changes in membrane potential. By responding to a threshold in the membrane potential, these voltage sensors trigger the opening of the channels. Which of the following best describes the behavior of a population of channels exposed to such a threshold? a. Some channels remain closed and some open completely. b. All channels open completely. c. All channels open partly, to the same degree. d. All channels open partly, each to a different degree.

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? (a) 2-methylpropane (b) acetone (c) methanol (d) urea

We can test the relative permeability of a phospholipid bilayer by using a synthetic membrane that does not contain any protein components. Some uncharged, polar molecules are found to diffuse freely across these membranes, to varying degrees. Which of the following has the lowest rate of diffusion across an artificial membrane? (a) glucose (b) water (c) glycerol (d) ethanol

What is the functional connection between the nucleolus, nuclear pores, and the nuclear membrane? a. Subunits of ribosomes are assembled in the nucleolus and pass through the nuclear membrane via the nuclear pores. b. The nuclear pores are connections between the nuclear membrane and the endoplasmic reticulum that permit ribosomes to assemble on the surface of the ER. c. The nucleolus contains messenger RNA (mRNA), which crosses the nuclear envelope through the nuclear pores. d. Endoplasmic reticulum membrane is produced in the nucleolus and leaves the nucleus through the nuclear pores. e. none of the above

What is the role of the nuclear localization in a nuclear protein? a. It is bound by cytoplasmic proteins that direct the nuclear protein to the nuclear pore. b. It is hydrophobic sequence that enables the protein to enter the nuclear membrane. 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.

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 aids in protein unfolding so that the protein can thread through nuclear pores. c. It prevents the protein from diffusing out of the nucleus through nuclear pores. d. It is a hydrophobic sequence that enables the protein to enter the nuclear membranes.

What purpose does the phosphorylation of glucose to glucose 6-phosphate by the enzyme hexokinase serve as the first step in glycolysis? (a) It helps drive the uptake of glucose from outside the cell. (b) It generates a high-energy phosphate bond.(c) It converts ATP to a more useful form. (d) It enables the glucose 6-phosphate to be recognized by phosphofructokinase, the next enzyme in the glycolytic pathway.

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.

When glucose is being used up and not replaced from food intake, the blood sugar level can be maintained by synthesizing glucose from smaller molecules such as pyruvate or lactate. This process is called gluconeogenesis. Which organ is principally responsible for supplying glucose to the rest of the body when glucose reserves are low? (a) liver (b) pancreas (c) spleen (d) gall bladder

Which is the toughest and most durable of the three types of cytoskeletal filaments? (a) Intermediate filaments (b) microtubules (c) actin filaments

Which molecule is more likely to diffuse through the lipid bilayer? a. glycerol b. RNA

Which of the following about Rb tumor suppressor protein is correct? (a) It binds E2F transcription factor and prevents cell from entering S phase until a mitogenic signal is received (b) It is activated when phosphorylated by Cdk (c) It is a transcription factor (d) When a mitogenic signal is received, it binds the transcription factor E2F and thus stimulates the cell to enter S phase

Which of the following apply to intercellular junctions? a. The three major adhesive junctions of animal cells are adherens junctions, desmosomes and hemidesmosomes. b. Desmosomes and hemidesmosomes connect epithelial cells to their basement membrane and adjacent cells respectively. c. Gap junctions and plasmodesmata are homologous structures. d. The junctional complexes of gastrointestinal enterocytes ensure that nutrients are only absorbed through the spaces between the cells, which prevents them absorbing potentially harmful substances.

Which of the following cells rely exclusively on glycolysis to supply them with ATP? (a) anaerobically growing yeast (b) aerobic bacteria (c) skeletal muscle cells (d) plant cells

Which of the following channels would not be expected to generate a change in voltage by movement of it's substrate across the membrane where it is found? a. An aquaporin b. A sodium channel c. A calcium channel d. A proton channel

Which of the following correctly compares the extracellular matrix (ECM) of animal cells to cell walls of plant cells? a. Both the ECM and the plant cell wall are composed of varying mixtures of proteins and carbohydrates. b. The structures that are external to the plasma membrane are essentially independent of the plasma membrane in both groups. c. The ECM and plant cell walls completely cover the plasma membrane of their respective cells. d. Both the ECM and plant cell walls provide rigid structures that determine the shape of their respective cells. e. Cell walls and ECMs provide for tight contact between adjacent cells.

Which of the following could be coded by a tumor-supressor gene? (a) A protein that helps prevent progression through cell cycle (b) A protein that helps prevent apoptosis (c) A protein that codes for a DNA repair enzyme (d) A protein that forms part of a growth factor signaling pathway

Which of the following does not occur before a eukaryotic mRNA is exported from the nucleus? a. The ribosome binds to the mRNA. b. The mRNA is polyadenylated at its 3′ end. c. A guanine nucleotide with a methyl group is added to the 5′ end of the mRNA. d. RNA polymerase dissociates.

Which of the following has the lowest rate of diffusion across an artificial membrane? a. Glucose b. Water c. Glycerol d. Ethanol

Which of the following is not a feature commonly observed in α helices? (a) left-handedness (b) one helical turn every 3.6 amino acids (c) cylindrical shape (d) amino acid side chains that point outward

Which of the following items is not important for flagellar movement? (a) sarcoplasmic reticulum (b) ATP (c) dynein (d) microtubules

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

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? a. 5′-CCCUAAAAAAAAAAAAAAAAUUUUUUUUUUUUUUUUAGGG-3′ b. 5′-UGUGUGUGUGUGUGUGUGUGUGUGUGUGUGUGUGUGUGUG-3′ c. 5′-AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA-3′ d. 5′-GGAAAAGGAGAUGGGCAAGGGGAAAAGGAGAUGGGCAAGG-3′

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.

Which of the following statements about microtubules is true? (a) Motor proteins move in a directional fashion along microtubules by using the inherent structural polarity of a protofilament. (b) The centromere nucleates the microtubules of the mitotic spindle. (c) Because microtubules are subject to dynamic instability, they are used only for transient structures in a cell. (d) ATP hydrolysis by a tubulin heterodimer is important for controlling the growth of a microtubule.

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 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.

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.

Which of the following statements about the function of the centrosome is false? (a) Microtubules emanating from the centrosome have alternating polarity such that some have their plus end attached to the centrosome while others have their minus end attached to the centrosome. (b) Centrosomes contain hundreds of copies of the γ-tubulin ring complex important for microtubule nucleation. (c) Centrosomes typically contain a pair of centrioles, which is made up of a cylindrical array of short microtubules. (d) Centrosomes are the major microtubule-organizing center in animal cells.

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

Which of the following statements about vesicle budding from the Golgi is false? a. Clathrin molecules are important for binding to and selecting cargos 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.

Which of the following statements are TRUE about signal molecules and receptors. (there could be more than one correct answer) a. Signals can bind to receptors at the plasma membrane or inside the cell. b. A signaling molecule will have the same effect on different cells. c. Signal specificity is entirely dependent on where the signal is released. d. There is only one type of receptor for each signaling molecule.

Which of the following statements is true about the Na+-K+ pump? a. The movement of Na+ and K+ requires ATP hydrolysis. b. It is a coupled transporter whereby K+ moving down its concentration gradient drives Na+ movement against its concentration gradient. c. The Na+-K+ pump is a symport. d. The Na+-K+ pump brings Na+ and K+ from the intestinal lumen into intestinal epithelial cells. e. The Na+-K+ pump is driven by absorption of photons.

Which of the following statements is true? a. Extracellular signal molecules that are hydrophilic must bind to a cell-surface 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.

Which of the situations below will enhance microtubule shrinkage? (a) addition of a drug that inhibits GTP exchange on free tubulin dimers (b) addition of a drug that inhibits hydrolysis of the GTP carried by tubulin dimers (c) addition of a drug that increases the affinity of tubulin molecules carrying GDP for other tubulin molecules (d) addition of a drug that blocks the ability of a tubulin dimer to bind to γ-tubulin

Which of these cell junctions form a barrier to the passage of materials? a. tight junctions b. gap (communicating) junctions c. desmosomes (anchoring junctions) d. keratin fibers e. plasmodesmata

Which phrase that is likely to occur more rapidly in response to an extracellular signal? a. changes in cell secretion/ increased cell division b. changes in protein phosphorylation/ changes in proteins being synthesized c. changes in mRNA levels/ changes in membrane potential

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

_____ aid in the coordination of the activities of adjacent animal cells. a. Gap (communicating) junctions b. Tight junctions c. Keratin fibers d. Plasmodesmata e Desmosomes

Which of the following can readily pass through a lipid bilayer (without assistance from any proteins)? (there can be more than 1 correct answer for this question) a. small hydrophobic molecules like gases b. small polar molecules that have no charge, such as ethanol c. large, uncharged polar molecules, such as glucose d. small ions, such as Na+

a, b

Which of the following statements describe certain properties of a passive transporter and the molecule it moves across the membrane? (There may be more than one correct answer) a. The transporter binds to the molecule prior to transferring it across the membrane b. The molecule transported can go either direction across the membrane, depending on the concentration gradient. c. The direction the molecule move across the membrane is determined by the orientation of the transporter. d. The transporter requires ATP to function. e. The transported molecule diffuses through an open pore in the membrane.

a, b

What does a target cell require to respond to an extracellular signal molecule? (Select all the correct answers) a. Access to the signal molecule (molecule present at location of cell) b. The presence of an appropriate receptor for the signal molecule c. Appropriate intracellular signaling pathways d. The extracellular signal molecule must get transported to the inside of the cell

a, b, c

Which of the following form part of the endomembrane system? Please select all that apply. a) Outer chloroplast membrane b) Lysosomal membrane c) Golgi apparatus d) Outer hydrogenosome membrane

a, b, c

Which of the following might legitimately be considered part of the endomembrane system? Please select all that apply. a) Rough endoplasmic reticulum b) Transitional endoplasmic reticulum c) Smooth endoplasmic reticulum d) Outer mitochondrial membrane

a, b, c

Membrane proteins may be attached to the membrane by which of the following types of interaction? Please select all that apply. a. Ionic interactions (salt links) b. Hydrophobic interactions c. α helical or α sheet domains containing hydrophobic amino acid residues are used to attach some types of membrane proteins to the lipid bilayer. d. Covalent bonds with membrane lipids

a, b, c, d

Which of the following components of biological membrane are amphipathic? Please select all that apply. a. Integral membrane proteins b. Phospholipids c. Glycolipids d. Membrane steroids such as cholesterol, sitosterol and ergosterol

a, b, c, d

Secretory cells that release relatively large quantities of glycoproteins contain relatively large amounts of which of the following? Please select all that apply. a) Rough endoplasmic reticulum b) Smooth endoplasmic reticulum c) Golgi apparatus d) Mitochondria

a, b, d

Which of the following statements are true of the group of signalling molecules called eicosanoids? Please select all that apply. a. Eicosanoids are derivatives of arachidonic acid. b. Eicosanoids include prostaglandins, thromboxanes and leukotrienes. c. Eicosanoids are usually autocrine signalling molecules. d. Eicosanoids can be synthesized from fatty acids derived from membrane phospholipids.

a, b, d

The __________________ 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 __________________ 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. The __________________ has a cis and trans face and receives proteins and lipids from the __________________, a system of interconnected sacs and tube of membranes that typically extends throughout the cell. a. cytosol b. Golgi apparatus c. nucleus d. endoplasmic reticulum e. lysosome f. peroxisomes g. endosomes h. mitochondria i. plasma membrane

a, g, e, b, d

3 subunits of trimeric G-proteins

alpha, beta, gamma

What would happen in each of the following case: You change the hydrophobic amino acids in an ER signal sequence into charged amino acids. (Assume that the protein involved is a soluble protein, not a membrane protein.)

altered signal sequence not recognized, protein remains in cytosol

7-10 Intermediate filaments are made from elongated fibrous proteins that are assembled into a ropelike structure. Figure Q17-10 shows the structure of an intermediate filament subunit. You are interested in how intermediate filaments are formed, and you create an intermediate filament subunit whose α-helical region is twice as long as that of a normal intermediate filament by duplicating the normal α-helical region while keeping a globular head at the N-terminus and a globular tail at the C-terminus; you call this subunit IFαd. If you were to assemble intermediate filaments using IFαd as the subunit, which of the following predictions describes the most likely outcome? Figure Q17-10 (a) Filaments assembled using IFαd will interact with different cytoskeletal components. (b) Filaments assembled using IFαd will form dimers that are twice as long as dimers assembled from normal intermediate filaments. (c) Sixteen tetramers assembled from IFαd will be needed for a ropelike structure to form. (d) Dimers of IFαd will form by interactions with the N-terminal globular head and the C-terminal globular tail.

A bacterium is suddenly expelled from a warm human intestine into the cold world outside. Which of the following adjustments might the bacterium make to maintain the same level of membrane fluidity? (a) Produce lipids with hydrocarbon tails that are longer and have fewer doublebonds. (b) Produce lipids with hydrocarbon tails that are shorter and have more double bonds. (c) Decrease the amount of cholesterol in the membrane. (d) Decrease the amount of glycolipids in the membrane.

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.

Active transport requires the input of energy into a system so as to move solutes against their electrochemical and concentration gradients. Which of the following is not one of the common ways to perform active transport? a. Na+-coupled b. K+-coupled c. ATP-driven d. light-driven

Although the extracellular environment has a high sodium ion concentration and the intracellular environment has a high potassium ion concentration, both must be neutralized by negatively charged molecules. In the extracellular case, what is the principle anion? a. HCO3- b. Cl- c. PO4^3- d. OH-

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.

Ca2+ pumps in the plasma membrane and endoplasmic reticulum are important for _____________. a. maintaining osmotic balance b. preventing Ca2+ from altering the activity of molecules in the cytosol c. providing enzymes in the endoplasmic reticulum with Ca2+ions that are necessary for their catalytic activity d. maintaining a negative membrane potential

Cells use membranes to help maintain set ranges of ion concentrations inside and outside the cell. Which of the following ions is the most abundant inside a typical mammalian cell? (a) Na+ (b) K+ (c) Ca2+ (d) Cl-

Consider the mechanism by which actin and tubulin polymerize. Which of the items below does not describe something similar about the polymerization mechanisms of actin and microtubules? (a) Although both filaments can grow from both ends, the growth rate is faster at the plus ends. (b) Depolymerization initiates at the plus ends of filaments. (c) Nucleotide hydrolysis promotes depolymerization of filaments. (d) Free subunits (actin and tubulin) carry nucleoside triphosphates.

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. 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

Fatty acids can easily be used to generate energy for the cell. Which of the following fatty acids will yield more energy? Explain your answer. (a) CH3-CH2-CH2-CH2-CH2-CH2-CH2-CH=CH-COOH (b) CH3-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-COOH (c) CH3-CH=CH-CH2-CH2-CH2-CH2-CH=CH-COOH (d) CH3-CH2-CH2-CH2-CH2-CH2-CH2-COOH

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? 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

Figure Q17-57 shows an electron micrograph of a skeletal muscle fiber, where various points along a fiber and various regions have been labeled. Figure Q17-57 Which of the following statements is true about muscle contraction? (a) Point A will move closer to point B. (b) Point B will move closer to point C. (c) Region D will become smaller. (d) Region E will shrink in size.

Formation of a lipid bilayer might seem to be energetically unfavorable. However, this arrangement is actually favored because it allows a higher level of entropy than any other alternative. What makes bilayer formation energetically favorable? (a) Polar head groups form a hydrogen bonding network at the interface with water. (b) Water molecules form cage-like structures around hydrophobic molecules. (c) Hydrogen bonds form between neighboring polar head groups in the bilayer. (d) Fatty acid tails are highly saturated and flexible.

How does Ras oncogene contribute to cancers? (a) It codes for an anti-apoptotic protein, produced in abnormally large amounts (b) It codes for a GTPase switch protein, which in its mutated form cannot be switched off (c) It codes for a transcription factor produced abnormally in large amounts (d) A growth factor that is continually active is encoded in its truncated form

If GTP hydrolysis occurs on a tubulin molecule at the plus end of a microtubule protofilament before another tubulin molecule is added, what typically happens to the microtubule? (a) The microtubule polymerizes (b) The microtubule depolymerizes. (c) The microtubule remains the same size.

In a cell, if you found DNA that was primarily nucleosome free, you reasonably conclude that this was ___________. a. heterochromatin b. euchromatin

In eukaryotic cells, the cell cortex is made of (a) a network of microtubules (b) a network of actin filaments

In eukaryotic flagellum, the bending of microtubules is driven by: (a) the basal body (b) the motor protein ciliary dynein (c) the fluid that surrounds the flagellum (d) actin and myosin

In humans, glycogen is a more useful food-storage molecule than fat because _____________________. (a) a gram of glycogen produces more energy than a gram of fat. (b) it can be utilized to produce ATP under anaerobic conditions, whereas fat cannot. (c) it binds water and is therefore useful in keeping the body hydrated. (d) for the same amount of energy storage, glycogen occupies less space in a cell than does fat.

In which phase of cell cycle is DNA replicated? (a) G1 phase (b) S phase (c) G2 phase (d) M phase

Intermediate filaments are made from elongated fibrous proteins that are assembled into a ropelike structure. Figure Q17-10 shows the structure of an intermediate filament subunit. You are interested in how intermediate filaments are formed, and you create an intermediate filament subunit whose α-helical region is twice as long as that of a normal intermediate filament by duplicating the normal α-helical region while keeping a globular head at the N-terminus and a globular tail at the C-terminus; you call this subunit IFαd. If you were to assemble intermediate filaments using IFαd as the subunit, which of the following predictions describes the most likely outcome?Figure Q17-10 (a) Filaments assembled using IFαd will interact with different cytoskeletal components. (b) Filaments assembled using IFαd will form dimers that are twice as long as dimers assembled from normal intermediate filaments. (c) Sixteen tetramers assembled from IFαd will be needed for a ropelike structure to form. (d) Dimers of IFαd will form by interactions with the N-terminal globular head and the C-terminal globular tail.

Intermediate filaments help protect animal cells from mechanical stress because ____________. (a) filaments directly extend from the interior of the cell to the extracellular space and into the next cell, linking one cell to the next, helping to distribute locally applied forces. (b) filaments in each cell are indirectly connected to the filaments of a neighboring cell through the desmosome, creating a continuous mechanical link between cells. (c) filaments remain independent of other cytoskeletal elements and keep the mechanical stress away from other cellular components. (d) filaments make up the desmosome junctions that connect cells; these junctions are more important than the internal network of filaments for protecting cells against mechanical stress.

Ion channels are classified as membrane transport proteins. Channels discriminate by size and charge. In addition to Na+, which of the following ions would you expect to be able to freely diffuse through a Na+ channel? a. Mg2+ b. H+ c. K+ d. Cl-

Migration of cancerous cells from the site of origin to other part of the body forming secondary tumors is called (a) Diapedesis (b) Metastasis (c) Proliferation (d) Apoptosis

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

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

Motor proteins use ATP hydrolysis to move. Which of the related statements is FALSE? a. Hydrolysis of bound ATP orders conformational change. b. ATP hydrolysis creates an irreversible step. c. A conformational change using ATP can reverse of direction of movement. d. This cellular process can be recreated in the laboratory to study.

Of the following organelles associated with the endomembrane system, which group is primarily involved in synthesizing molecules needed by the cell? a. lysosome, vacuole, ribosome b. ribosome, rough endoplasmic reticulum, smooth endoplasmic reticulum c. vacuole, rough endoplasmic reticulum, smooth endoplasmic reticulum d. smooth endoplasmic reticulum, ribosome, vacuole e. rough endoplasmic reticulum, lysosome, vacuole

Passage of a cell through stages of cell cycle is controlled by a protein kinase that phosphorylates many different proteins at appropriate times (a) Cdk activating kinase (b) Cyclin-dependent kinase (c) Cyclins (d) Tyrosine kinase

Programmed cell death is termed as (a) Metastasis (b) Apoptosis (c) Proliferation (d) Mitotic termination

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? a. on the surface of the protein b. inside a cavity on the protein surface c. buried in the interior of the protein d. forms on the surface of the protein in the presence of ligand

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

Ribosomal subunits are manufactured by the _____. a. lysosome b. nucleolus c. peroxisome d. rough endoplasmic reticulum e. smooth endoplasmic reticulum

Several different classes of enzymes are needed for the catabolism of carbohydrates. Which of the following descriptions best matches the function of a mutase? (a) An enzyme that catalyzes the rearrangement of bonds within a single molecule. (b) An enzyme that catalyzes a change in the position of a specific chemical group within a single molecule. (c) An enzyme that catalyzes the oxidation of a molecule by removing a hydride ion. (d) An enzyme that catalyzes the addition of phosphate groups to other molecules.

Step 6 of the citric acid cycle is catalyzed by succinate dehydrogenase. Keeping in mind that dehydrogenases catalyze redox reactions, which are the products of the reaction in which succinate is oxidized? (a) fumarate, NADH (b) fumarate, FADH2 (c) fumarate, FADH2 (d) succinyl CoA, NADH

Steps 7 and 10 of glycolysis result in substrate-level phosphorylation. Which of the following best describes this process? (a) ATP is being hydrolyzed to phosphorylate the substrate. (b) The energy derived from substrate oxidation is coupled to the conversion of ADP to ATP. (c) Two successive phosphates are transferred, first to AMP, then to ADP, finally forming ATP. (d) The substrate is hydrolyzed using ATP as an energy source.

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? a. increase in gene expression b. gene silencing c. recruitment of remodeling complexes d. displacement of histone H1

The __________ __________ is responsible for transporting, modifying, and packaging proteins and lipids into vesicles for delivery to targeted destinations. a. plasma membrane b. Golgi network c. mitochondrial membrane d. nuclear envelope

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.

The concentration of H+ ions inside the mitochondrial matrix is lower than it is in the cytosol or the mitochondrial intermembrane space. What would be the immediate effect of a membrane-permeable compound that carries and releases protons into the mitochondrial matrix? (a) inhibition of the electron-transport chain (b) inhibition of ATP synthesis (c) increased import of ADP into the matrix (d) inhibition of the citric acid

The concentration of actin monomers is high in the cytosol. What keeps these monomers from polymerizing totally into filaments? a) The concentration is high, but not high enough for polymerization to occur. b) The monomers are bound by proteins that prevent their polymerization. c) Not enough of the monomers are bound to ATP.

The cytoskeleton provides support, structure, motility, and organization, and it forms tracks to direct organelle and vesicle transport. Which of the cytoskeletal elements listed below helps segregate chromosomes in a dividing animal? a. actin filaments b. microtubules c. intermediate filaments d. none of the above (all have the same thickness)

The figure below 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-termini in the cytoplasm. d. None of the above.

The final metabolite produced by glycolysis is ___________. (a) acetyl CoA. (b) pyruvate. (c) 3-phosphoglycerate. (d) glyceraldehyde 3-phosphate.

The first energy-generating steps in glycolysis begin when glyceraldehyde 3-phosphate undergoes an energetically favorable reaction in which it is simultaneously oxidized and phosphorylated by the enzyme glyceraldehyde 3-phosphate dehydrogenase to form 1,3-bisphosphoglycerate, with the accompanying conversion of NAD+ to NADH. In a second energetically favorable reaction catalyzed by a second enzyme, the 1,3-bisphosphoglycerate is then converted to 3-phosphoglycerate, with the accompanying conversion of ADP to ATP. Which of the following statements is true about this reaction? (a) The reaction glyceraldehyde 3-phosphate 1,3-bisphosphoglycerate should be inhibited when levels of NADH fall. (b) The ΔG° for the oxidation of the aldehyde group on glyceraldehyde 3-phosphate to form a carboxylic acid is more negative than the ΔG° for ATP hydrolysis. (c) The energy stored in the phosphate bond of glyceraldehyde 3-phosphate contributes to driving the reaction forward. (d) The cysteine side chain on the enzyme is oxidized by NAD+.

The following statement is consistent with which type(s) of microtubule? "It is nucleated at the centrosome." (a) cilliary (or flagellar) microtubule (b) mitotic spindle microtubule (c) both a and b (d) none of the above

The full three-dimensional conformation formed by the entire polypeptide chain, which could include both β sheets, alpha helices and various loops/turns in considered what level of organization? a. primary structure b. secondary structure c. tertiary structure d. quaternary structure

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

The hydrolysis of bound ATP to ADP in an actin filament _____ the strength of binding between monomers in the filament. (a) increases (b) decreases (c) has no effect

The lateral movement of transmembrane proteins can be restricted by several different mechanisms. Which mechanism best describes the process by which a budding yeast cell designates the site of new bud formation during cell division? Select one: a. proteins are tethered to the extracellular matrix b. proteins are tethered to the cell cortex c. proteins are tethered to the proteins on the surface of another cell d. protein movement is limited by the presence of a diffusion barrier

The observation that chloroplasts and mitochondria each contain their own DNA and synthesize some of the proteins that function in these organelles suggests that chloroplasts and mitochondria ______. a. are produced by the nucleus of the cell b. must divide each time the cell containing them divides c. are part of the endomembrane system d. are involved in energy metabolism of the cell e. contain two or more membranes

The oxygen-dependent reactions required for cellular respiration were originally thought to occur in a linear pathway. By using a competitive inhibitor for one enzyme in the pathway, investigators discovered that these reactions occur in a cycle. Which product in the reaction pathway builds up when the inhibitor is added? (a) citrate (b) succinate (c) fumarate (d) malate

The phosphorylation of a protein is typically associated with a change in activity, the assembly of a protein complex, or the triggering of a downstream signaling cascade. The addition of ubiquitin, a small polypeptide, is another type of covalent modification that can affect the protein function. Ubiquitylation often results in a. membrane association. b. protein degradation. c. protein secretion. d. nuclear translocation.

The rate of an enzyme reaction (V) increases as the substrate concentration increases, until a maximum value (Vmax) is reached. At this point, which of the following is FALSE? a. all substrate-binding sites on the enzyme molecules are fully occupied b. the rate of the reaction is not limited by the rate of the catalytic process of the enzyme c. the concentration of substrate at which the reaction rate is half-maximal (KM) is a direct measure of how tightly the substrate is bound d. a large value of KM (a large amount of substrate needed) corresponding to weak binding.

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)? (a) 24 carbons with 1 double bond (b) 15 carbons with 2 double bonds (c) 20 carbons with 2 double bonds (d) 16 carbons with no double bonds

To study how proteins fold, scientists must be able to purify the protein of interest, use solvents to denature the folded protein, and observe the process of refolding at successive time points. What is the effect of the solvents used in the denaturation process? a. The solvents break all covalent interactions. b. The solvents break all noncovalent interactions. c. The solvents break some of the noncovalent interactions, resulting in a misfolded protein.d.The solvents create a new protein conformation.

We know the detailed molecular structure and mechanism of action of the transmembrane protein bacteriorhodopsin. This protein uses sunlight as the source of energy to pump ______ out of the cell. (a) 4 ATP (b) 7 H+ (c) 7 K+ (d) 4 Na+

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.

Where does most new membrane synthesis take place in a eukaryotic cell? (a) in the Golgi apparatus (b) in the endoplasmic reticulum (c) in the plasma membrane (d) in the mitochondria (e) on ribosomes

Where is calcium stored? a. mitochondria b. smooth endoplasmic reticulum c. centrioles d. rough endoplasmic reticulum e. microtubules

Which end of a microtubule is embedded in the centrosome? (a) The plus end (b) The minus end

Which molecule is more likely to diffuse through the lipid bilayer? a. Cl- b. ethanol

Which molecule is more likely to diffuse through the lipid bilayer? a. H2O b. O2

Which molecule is more likely to diffuse through the lipid bilayer? a. amino acids b. benzene

Which of the following best describes the behavior of a gated channel? Select one: a. It stays open continuously when stimulated. b. It opens more frequently in response to a given stimulus. c. It opens more widely as the stimulus becomes stronger. d. It remains closed if unstimulated.

Which of the following conditions is likely to decrease the likelihood of skeletal muscle contraction? (a) partial depolarization of the T-tubule membrane, such that the resting potential is closer to zero (b) addition of a drug that blocks Ca2+ binding to troponin (c) an increase in the amount of ATP in the cell (d) a mutation in tropomyosin that decreases its affinity for the actin filament

Which of the following cytoskeletal structures grows out from a centrosome toward the cell periphery? (a) intermediate filaments (b) microtubules (c) actin filaments

Which of the following cytoskeletal structures makes up the mitotic spindle? (a) intermediate filaments (b) microtubules (c) actin filaments

Which of the following cytoskeletal structures provides tracks for guiding intracellular transport? (a) intermediate filaments (b) microtubules (c) actin filaments

Which of the following describes the structure of an actin filament? (a) It is a hollow cylinder made up of actin molecules (b) It is a twisted chain of actin molecules (c) It is a structure with a long tail and two globular heads

Which of the following does not occur at the initiation of transcription? a. TBP is part of TFIID. b. TFIIB binds to the promoter first and helps RNA polymerase II initiate transcription. c. When TBP binds the TATA box it causes the DNA to bend sharply d. TFIID is the first component of the pre-initiation complex to bind the promoter

Which of the following ions is the most abundant inside a typical mammalian cell? a. Na+ b. K+ c. Ca^2+ d. Cl-

Which of the following is (are) most likely to be involved in the process of producing proteins for a chloroplast or mitochondrion, neither of which is part of the endomembrane system? a. transport vesicles b. free cytoplasmic ribosomes c. the Golgi apparatus d. rough endoplasmic reticulum e. smooth endoplasmic reticulum

Which of the following is NOT a feature commonly observed in β sheets? a. antiparallel regions b. coiled-coil patterns c. extended polypeptide backbone d. parallel regions

Which of the following occur without coupling transport of the solute to the movement of a second solute? a. import of glucose into gut epithelial cells b. export of Ca2+ from the cytosol c. export of H+ from animal cells for pH regluation d. the export of Na+ from cells to maintain resting membrane potential

Which of the following organelles has both an outer and an inner membrane? a. endoplasmic reticulum b. mitochondrion c. lysosome d. peroxisome

Which of the following phospholipid precursors is the most hydrophobic? Select one: a. phosphate b. triacylglycerol c. glycerol d. diacylglycerol

Which of the following plasma membrane receptors activate signalling pathways usually by forming molecular dimers that result in protein phosphorylation reactions upon binding of their specific ligand? a. Steroid hormone receptors b. Receptor tyrosine kinases c. Ligand-gated ion channels d. G protein-coupled receptors

Which of the following polymers of glucose is used as a vehicle to store energy reserves in animal cells? (a) glucagon (b) glycogen (c) starch (d) glycerol

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

Which of the following statements about organellar movement in the cell is false? (a) Organelles undergo saltatory movement in the cell. (b) Only the microtubule cytoskeleton is involved in organellar movement. (c) Motor proteins involved in organellar movement use ATP hydrolysis for energy. (d) Organelles are attached to the tail domain of motor proteins.

Which of the following statements about skeletal muscle contraction is false? (a) When a muscle cell receives a signal from the nervous system, voltagegated channels open in the T-tubule membrane. (b) 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. (c) A change in the conformation of troponin leads to changes in tropomyosin such that it no longer blocks the binding of myosin heads to the actin filament. (d) During muscle contraction, the Z discs move closer together as the myosin heads walk toward the plus ends of the actin filaments.

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 the smooth ER. c. Steroid hormones are synthesized on the smooth ER. d. The ER membrane is contiguous with the outer nuclear membrane.

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.

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. Signal peptidase will remove the signal sequence once the protein has been imported into these organelles. d. Proteins that are transported into these organelles are unfolded as they are being transported.

Which of the following statements best reflects the nature of synaptic plasticity? a. new synapses are created due to the postnatal generation of neurons b. synaptic response changes in magnitude depending on frequency of stimulation c. there is a change in the type of neurotransmitter used at the synapse. d. neuronal connections are pruned during normal development

Which of the following statements is false? (a) Cytochalasins prevent actin polymerization. (b) Actin filaments are usually excluded from the cell cortex. (c) Integrins are transmembrane proteins that can bind to the extracellular matrix. (d) ARPs can promote the formation of branched actin filaments

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 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.

Which of the following statements is true? Select one: a. Phospholipids will spontaneously form liposomes in nonpolar solvents b. Membrane lipids diffuse within the plane of the membrane. c. Membrane lipids frequently flip- flop between one monolayer and the other. d. In eukaryotes, all membrane-enclosed organelles are surrounded by one lipid bilayer

Which one of the following organelles is unlikely to show enhanced abundance in the pancreatic cells that secrete large amounts of digestive enzymes? a. rough endoplasmic reticulum b. free cytoplasmic ribosomes c. Golgi apparatus d. transport vesicles e. All of the above will increase in pancreatic cells secreting digestive enzymes.

Which property of p53 enables it to prevent the development of cancer? (a) It is a transcription factor that causes protein production which stimulates the cell cycle (b) It prevents replication of cells with damaged DNA (c) It prevents cells from triggering apoptosis (d) It stimulates synthesis of DNA repair enzymes that replace telomere sequence lost during cell division

With respect to their surrounding membrane system, which is the odd one out? a) Nucleus. b) Endoplasmic reticulum. c) Mitochondria. d) Chloroplasts.

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.

You discover a protein, MtA, and find that it binds to the plus ends of microtubules in cells. The hypothesis that best explains this localization is ________________. (a) MtA is involved in stabilizing microtubules. (b) MtA binds to GTP-bound tubulin on microtubules. (c) MtA is important for the interaction of microtubules with the centrosome. (d) MtA will not bind to purified microtubules in a test tube.

You have generated antibodies that recognize the extracellular domain of the Ca2+ pump. Adding these antibodies to animal cells blocks the active transport of Ca2+ from the cytosol into the extracellular environment. What do you expect to observe with respect to intracellular Ca2+? Select one: a. Ca2+ pumps in vesicles membranes keep cystosolic calcium levels low. b. Ca2+ pumps in the ER membrane keep cystosolic calcium levels low. c. Ca2+ pumps in the Golgi apparatus keep cystosolic calcium levels low. d. Ca2+ concentrations in the cytosol increase at a steady rate.

You would expect a cell with an extensive Golgi apparatus to _____. a. make a lot of ATP b. secrete a lot of protein c. move rapidly d. perform photosynthesis e. store large quantities of ions

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 was not listening carefully when he was told about the molecular defect of this cell line. He is 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. adaptin b. dynamin c. Rab d. clathrin

_______ ion channels are found in the hair cells of the mammalian cochlea. a. Ligand gated b. Stress gated c. Voltage gated

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. Proteins enter the nucleus in their __________________ form. Proteins that remain in the cytosol do not contain a __________________. Proteins are transported into the Golgi apparatus via __________________. The proteins transported into the endoplasmic reticulum by __________________ are in their __________________ form. a. amino acid sequence b. endoplasmic reticulum c. folded d. Golgi apparatus e. plasma membrane f. protein translocators g. sorting signal h. transport vesicles i. unfolded

b, a, c, g, h, f, i

Which of the following statements are correct? Please select all that apply. a. Lysosomes are formed from Golgi-derived coatomer-coated vesicles. b. Lysosomal enzyme transport vesicles are able to fuse with late endosomes. c. The lowering of the pH in lysosomes, autophagosomes and phagosomes by an ATP-driven H+ pump in their membranes lowers their luminal pH and activates their digestive enzymes. d. The proteins of the lysosomal membrane are heavily glycosylated on their cytosolic surface giving them a dense oligosaccharide layer that protects the membrane from digestion.

b, c

Which of the following types of protein modification can occur in the ER but not in the a. cytosol. b. disulfide bond formation c. glycosylation d. phosphorylation e. hydrogen bonding

b, c

Which of the following applies to membrane lipids? Please select all that apply. a. Membrane lipids are composed of hydrophobic molecules. b. Scramblases and flippases are able to catalyze the transfer of lipid molecules between the outer and inner leaflets. c. Membrane lipids are able to spontaneously move between the outer and inner leaflets. d. Different lipid compositions are found in the two leaflets of a membrane.

b, d

Stable microtubules are used in cilia and flagella; these microtubules are nucleated from a __________________ and involve a "__________________ plus two" array of microtubules.

basal body, nine

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

A protein that ultimately functions in the plasma membrane of a cell is most likely to have been synthesized _____. a. on ribosomes on the nuclear envelope b. on free cytoplasmic ribosomes c. in the rough endoplasmic reticulum d. in the mitochondria e. in the plasma membrane

All of the different proteins in a cell are made from the same 20 __________. By linking them in different sequences, the cell can make protein molecules with different conformations and surface chemistries, and therefore different functions. a. nucleotides b. sugars c. amino acids d. fatty acids

Although the chromatin structure of interphase and mitotic chromosomes is very compact, DNA-binding proteins and protein complexes must be able to gain access to the DNA molecule. Chromatin-remodeling complexes provide this access by a. recruiting other enzymes. b. modifying the N-terminal tails of core histones. c. using the energy of ATP hydrolysis to move nucleosomes. d. denaturing the DNA by interfering with hydrogen-bonding between base pairs.

Approximately, how many distinct synapses are established on the dendrites and cell body of a motor neuron in the spinal cord? a. tens b. hundreds c. thousands d. milllions

Both glycoproteins and proteoglycans contribute to the carbohydrate layer on the surface of the cell. Which of the following is not true of glycoproteins? (a) They can be secreted into the extracellular environment. (b) They have only one transmembrane domain.(c) They have long carbohydrate chains. (d) They are recognized by lectins.

Cells use membranes to help maintain set ranges of ion concentrations inside and outside the cell. Which of the following negatively charged ions is not primarily used to buffer positive charges inside the cell? (a) PO_4^3- (b) OH- (c) Cl- (d) HCO3-

Compared to the normal situation, in which actin monomers carry ATP, what do you predict would happen if actin monomers that bind a nonhydrolyzable form of ATP were incorporated into actin filaments? a. Actin filaments would grow shorter because depolymerization would be enhanced. b. No change, as addition of monomers binding nonhydrolyzable ATP would not affect actin filament length. c. Actin filaments would grow longer. d. Actin filaments would grow shorter because new monomers could not be added to the filaments.

Consider a protein that is made in the rough endoplasmic reticulum. You observe that when the synthesis of the protein is completed, the protein is located in the ER membrane. Where else in the cell might this protein be found? a. in the aqueous interior of a lysosome functioning as a digestive enzyme b. in the cytoplasm, functioning as an enzyme in carbohydrate synthesis c. membrane functioning in the transport of molecules into the cell d. in the internal space of the Golgi apparatus, being modified before the protein is excreted e. in a mitochondrion functioning in ATP synthesis

Consider two genes that are next to each other on a chromosome, as arranged in Figure 7-1. Which of the following statements is TRUE? a. The two genes must be transcribed into RNA using the same strand of DNA. b. If gene A is transcribed in a cell, gene B cannot be transcribed. c. Gene A and gene B can be transcribed at different rates, producing different amounts of RNA within the same cell. d. If gene A is transcribed in a cell, gene B must be transcribed.

Dynamic instability in microtubules stems from the intrinsic capacity of tubulin molecules to hydrolyze: (a) peptide bonds (b) tubulin dimers (c) GTP (d) ATP

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. degraded by signal peptidase b. in the ER lumen c. in the cytoplasm d. inserted into the ER membrane

Figure Q17-40A shows how the movement of dynein causes the flagellum to bend. If instead of the normal situation, the polarity of the adjacent doublet of microtubules were to be reversed (see Figure Q17-40B), what do you predict would happen? Figure Q17-40 (a) No bending would occur. (b) Bending would occur exactly as diagrammed in Figure Q17-40A. (c) Bending would occur, except that the right microtubule doublet would move down relative to the left one. (d) The two microtubule doublets would slide away from each other

Figure Q17-52 shows the leading edge of a lamellipodium. Which of the following statements is false? Figure Q17-52 (a) Nucleation of new filaments near the leading edge pushes the plasma membrane forward. (b) ARP proteins nucleate the branched actin filaments in the lamellipodium. (c) Capping proteins bind to the minus end of actin filaments. (d) There is more ATP-bound actin at the leading edge than in the actin filaments away from the leading edge.

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.

Glyceraldehyde 3-phosphate dehydrogenase operates by stripping a hydride ion from its substrate. Which molecule is the recipient of the proton and two electrons during this transfer? (a) oxygen (b) acetyl CoA (c) NAD+ (d) FADH

Glycolysis generates more stored energy than it expends. What is the net number of activated carrier molecules produced in this process (number and type of molecules produced minus the number of those molecules used as input)? (a) 6 ATP, 2 NADH (b) 4 ATP, 4 NADH (c) 2 ATP, 2 NADH (d) 4 ATP, 2 NADH

If Na+ channels are opened in a cell that was previously at rest, how will the resting membrane potential be affected? a. The membrane potential is not affected by Na+. b. It becomes more negative. c. It becomes more positive. d. It is permanently reset.

In anaerobic conditions, skeletal muscle produces _____________. (a) lactate and CO2. (b) ethanol and CO2. (c) lactate only. (d) ethanol only.

In step 1 of the citric acid cycle, citrate is generated by the enzyme citrate synthase. The enzyme combines the two-carbon acetyl group from acetyl CoA and the four-carbon oxaloacetate. What is the source of energy that drives this reaction forward? (a) a high-energy phosphodiester bond (b) a transfer of high-energy electrons (c) a high-energy thioester bond (d) the heat of molecular collision

In step 4 of the citric acid cycle, the reduction of NAD+ to NADH is coupled to the generation of CO2 and the formation of a high-energy thioester bond. Which molecule provides the sulfhydryl group necessary to form the thioester bond? (a) pyruvate (b) acetyl CoA (c) CoA (d) cysteine side chain in the catalytic pocket

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

Intermediate filaments are found in what structure? (a) the mitotic spindle (b) centrosomes (c) desosomes (d) cilia

Intermediate filaments are: (a) tubelike structures (b) springlike structures. (c) ropelike structures. (d) meshlike structures.

Microtubules are: a) rope-like strands. b) mesh-like networks. c) hollow tubes. d) interlocking chains.

New membrane phospholipids are synthesized by enzymes bound to the _____________ side of the _________________ membrane. (a) cytosolic, mitochondrial (b) luminal, Golgi (c) cytosolic, endoplasmic reticulum (d) extracellular, plasma

Oncogenes do not encode for (a) Trans-membrane protein receptors (b) Growth factors (c) DNA-dependent RNA polymerase (d) Cytoplasmic G-proteins and protein kinases

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

Pyruvate is an important metabolic intermediate that can be converted into several other compounds, depending on which enzyme is catalyzing the reaction. Which of the following cannot be produced from pyruvate in a single enzyme-catalyzed reaction? (a) lactate (b) oxaloacetate (c) citrate (d) alanine

Several different classes of enzymes are needed for the catabolism of carbohydrates. Which of the following descriptions best matches the function of a dehydrogenase? (a) An enzyme that catalyzes the rearrangement of bonds within a single molecule. (b) An enzyme that catalyzes a change in the position of a specific chemical group within a single molecule. (c) An enzyme that catalyzes the oxidation of a molecule by removing a hydride ion. (d) An enzyme that catalyzes the addition of phosphate groups to other molecules.

Some cells have aquaporins---channels that facilitate the flow of water molecules through the plasma membrane. For these cells, what regulates the rate and direction of water diffusion across the membrane? a. Aquaporin conformation b. Resting montane potential c. Solute concentrations on either side of the membrane d. Availability of ATP

Some cells have aquaporins—channels that facilitate the flow of water molecules through the plasma membrane. For these cells, what regulates the rate and direction of water diffusion across the membrane? a. aquaporin conformation b. resting membrane potential c. solute concentrations on either side of the membrane d. availability of ATP

Splice sites in pre-mRNA are marked by two universally conserved sequences contained a. in the middle of the intron. b. at the ends of the exons. c. at the ends of the introns. d. none of the above

The Na+-K+ ATPase is also known as the Na+-K+ pump. It is responsible for maintaining the high extracellular sodium ion concentration and the high intracellular potassium ion concentration. What happens immediately after the pump hydrolyzes ATP? a. Na+ is bound. b. ADP is bound. c. The pump is phosphorylated. d. The pump changes conformation.

The advantage to the cell of the gradual oxidation of glucose during cellular respiration compared with its combustion to CO2 and H2O in a single step is that ________________. (a) more free energy is released for a given amount of glucose oxidized. (b) no energy is lost as heat. (c) energy can be extracted in usable amounts. (d) more CO2 is produced for a given amount of glucose oxidized.

The amino acid sequences below represent the sequences of transmembrane helices. The characteristics of α helices that form a channel are different from those that form a single transmembrane domain. Select the helix that forms a single transmembrane domain. Select one: a. VGHSLSIFTLVISLGIFVFF b. VTLHKNMFLTYILNSMIIII c. IMIVLVMLLNIGLAILFVHF d. ILHFFHQYMMACNYFWMLCE

The biosynthetic pathway for the two amino acids E and H is shown schematically in Figure 4-33. You are able to show that E inhibits enzyme V, and H inhibits enzyme X. Which biosynthetic product is most likely the inhibitor of enzyme T? a. H b. T c. C d. E

The drug taxol binds tightly to microtubules and prevents them from depolymerizing. The drug colchicine binds tightly to free tubulin and prevents its polymerization into microtubules. Which of these drugs arrests dividing cells in mitosis? (a) taxol (b) colchicine (c) both

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 following happens when a cell-surface 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 following happens when the G-protein-coupled receptor activates a G protein. a. The beta subunit exchanges its bound GDP for GTP. b. The GDP bound to the alpha subunit is phosphorylated to form bound GTP. c. The alpha subunit exchanges its bound GDP for GTP. d. It activates the alpha subunit and inactivates the By complex.

The following statement is consistent with which type(s) of microtubule? "It uses dynein motors." (a) cilliary (or flagellar) microtubule (b) mitotic spindle microtubule (c) both a and b (d) none of the above

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 intermediates of the citric acid cycle are constantly being depleted because they are used to produce many of the amino acids needed to make proteins. The enzyme pyruvate carboxylase converts pyruvate to oxaloacetate to replenish these intermediates. Bacteria, but not animal cells, have additional enzymes that can carry out the reaction acetyl CoA + isocitrate oxaloacetate + succinate. Which of the following compounds will not support the growth of animal cells when used as the major source of carbon in food, but will support the growth of nonphotosynthetic bacteria? (a) pyruvate (b) glucose (c) fatty acids (d) fructose

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.

The lateral movement of transmembrane proteins can be restricted by several different mechanisms. Which mechanism best describes the process by which nutrients are taken up at the apical surface of the epithelial cells that line the gut and released from their basal and lateral surfaces? Select one: a. proteins are tethered to the cell cortex b. proteins are tethered to the extracellular matrix c. protein movement is limited by the presence of a diffusion barrier d. proteins are tethered to the proteins on the surface of another cell

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

The microtubules in a cell form a structural framework that can have all the following functions except which one? (a) holding internal organelles such as the Golgi apparatus in particular positions in the cell (b) creating long, thin cytoplasmic extensions that protrude from one side of the cell (c) strengthening the plasma membrane (d) moving materials from one place to another inside a cell

The reaction cycle that uses acetyl CoA to generate electron carrier molecules needed in the electron-transport chain is important for powering the cell. Which of the names below is not one of those commonly used to describe this reaction cycle? (a) tricarboxylic acid cycle (b) Krebs cycle (c) oxaloacetic acid cycle (d) citric acid cycle

The target cells of a lipid soluble hormone such as cortisol, are able to respond to it because of which of the following? a) Their genome includes the appropriate transcriptional response elements. b) They have membrane bound cell surface receptors. c) Only target cells express appropriate cytosolic receptors. d) The hormone-receptor complex stimulates the phosphorylation/dephosphorylation of subsequent proteins in the signalling pathway.

Unlike soluble, cytosolic proteins, membrane proteins are more difficult to purify. Which of the following substances is most commonly used to help purify a membrane protein? (a) high salt solution (b) sucrose (c) detergent (d) ethanol

What is the name of the thin sheetlike structures that a fibroblast regularly extends during cell crawling? (a) Pseudopods (b) Filopodia (c) Lamellipodia (d) Phagosomes

What type of macromolecule helps package DNA in eukaryotic chromosomes? a. lipids b. carbohydrates c. proteins d. RNA

When the net charge on either side of the plasma membrane is zero, what else is true? (a) There is an equal number of K+ ions on each side of the plasma membrane. (b) The K+ leak channels are open. (c) The electrochemical potential across the membrane is zero. (d) The resting membrane potential is between -20 mV and -200 mV.

Which DNA base pair is represented in Figure 5-7? a. A-T b. T-A c. G-C d. C-G

Which of the following categories best describes the function of the rough endoplasmic reticulum? a. breakdown of complex foods b. energy processing c. manufacturing d. structural support of cells e. information storage

Which of the following enzymes breaks down proteins by hydrolyzing peptide bonds between amino acids? a. Ligase. b. Kinase. c. Protease. d. ATPase.

Which of the following gated ion channels are involved in inhibitory synaptic signaling? a. voltage-gated Na+ b. voltage-gated Ca2+ channels glycine-gated c. glycine-gated Cl- channels d. Glutamate-gated cation channels

Which of the following is FALSE about molecular chaperones? a. They assist polypeptide folding by helping the folding process follow the most energetically favorable pathway. b. They can isolate proteins from other components of the cells until folding is complete. c. They can interact with unfolded polypeptides in a way that changes the final fold of the protein from its normal conformation. d. They help streamline the protein-folding process by making it a more efficient and reliable process inside the cell.

Which of the following is the main function of intermediate filaments? (a) To provide tracks for guiding intracellular transport (b) To enable cells to crawl (c) To enable cells to withstand the mechanical stress that occurs when cells are stretched

Which of the following negatively charged ions is NOT primarily used to buffer positive charges inside the cell? a. PO4^3- b. OH- c. Cl- d. HCO3-

Which of the following organelles is not part of the endomembrane system? a. Golgi apparatus b. the endosome c. mitochondria d. lysosomes

Which of the following organelles lack membranes as part of their structure? a. vacuoles b. mitochondria c. microfilaments d. nucleus e. All of the choices are surrounded by membranes.

Which of the following organelles might be found inside other organelles? a. the nucleolus b. mitochondria c. ribosomes d. transport vesicles e. No organelles are found inside of other organelles.

Which of the following sequences represents the order in which a protein made in the rough endoplasmic reticulum might move through the endomembrane system? a. lysosome; plasma membrane b. Golgi apparatus; mitochondria c. Golgi apparatus; vacuole d. plasma membrane; nuclear envelope e. nuclear envelope; lysosome

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.

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

Which of the following statements about resting membrane potential is NOT true? a. The resting membrane potential for most animal cells is 0 mV, because the positive and negative ions are in balance. b. The resting membrane potential for most animal cells is positive, because Na+ ions are so plentiful inside cells. c. The resting membrane potential for most animal cells is negative, because the inside of the cell is more negatively charged than the outside of the cell. d. At the resting membrane potential, no ions enter or exit the cell.

Which of the following statements about the carbohydrate coating of the cell surface is false? (a) It is not usually found on the cytosolic side of the membrane. (b) It can play a role in cell-cell adhesion. (c) The arrangement of the oligosaccharide side chains is highly ordered, much like the peptide bonds of a polypeptide chain. (d) Specific oligosaccharides can be involved in cell-cell recognition.

Which of the following statements about the cytoskeleton is false? (a) The cytoskeleton is made up of three types of protein filaments. (b) The cytoskeleton controls the location of organelles in eukaryotic cells. (c) Covalent bonds between protein monomers hold together cytoskeletal filaments. (d) The cytoskeleton of a cell can change in response to the environment.

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

Which of the following statements is TRUE? a. Ribosomes are large RNA structures composed solely of protein. b. Ribosomes are synthesized entirely in the cytoplasm. c. rRNA contains the catalytic activity that joins amino acids together. d. A ribosome binds one tRNA at a time.

Which of the following statements is correct? Kinesins and dyneins ____________________. (a) have tails that bind to the filaments. (b) move along both microtubules and actin filaments. (c) often move in opposite directions to each other. (d) derive their energy from GTP hydrolysis.

Which of the following statements is true of Na+/K+-adenosine triphosphatases? a. They use the free energy from the hydrolysis of ATP to transport K+ out the cell and Na+ into the cell. b. They are tetramers, consisting of four equally sized polypeptide chains. c. They indirectly control the volume of the cell. d. Their actions maintain a membrane potential with a value often of approximately -60 mV; the interior of the cell being positive with respect to the exterior.

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 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 proteins translocators.

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.

Which of the following statements is true? a. The signal sequences on mitochondrial proteins are usually C-terminal. 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.

Which of the following statements is true? (a) Phospholipids will spontaneously form liposomes in nonpolar solvents. (b) In eukaryotes, all membrane-enclosed organelles are surrounded by one lipidbilayer. (c) Membrane lipids diffuse within the plane of the membrane. (d) Membrane lipids frequently flip-flop between one monolayer and the other.

Which of the following statements regarding cyclin-dependent protein kinase is not correct? (a) Their activity is regulated by cyclins (b) They can alter the activity of proteins involve in the progression of cells through cell cycle (c) Their activity fluctuates during cell cycle (d) Each type of cell contains one specific form (e) Their activity is regulated by changes in gene expression, protein phosphorylation and proteolysis

Which of the following steps or processes in aerobic respiration include the production of carbon dioxide? (a) breakdown of glycogen (b) glycolysis (c) conversion of pyruvate to acetyl CoA (d) oxidative phosphorylation

Which of the following structures shorten during muscle contraction? (a) myosin filaments (b) flagella (c) sarcomeres (d) actin filaments

Which of the following structures shorten during muscle contraction? a. myosin filaments b. flagella c. sarcomeres d. actin filaments

Which of the following types of intermediate filaments are found in all animal cells? (a) Keratins (b) Vimentin and vimentin-related filaments (c) Nuclear lamins (d) Neurofilaments

Which one of the following five membranes is most likely to have a lipid composition that is distinct from the other four? a. endoplasmic reticulum b. plasma membrane c. mitochondrial outer membrane d. lysosome membrane e. Golgi apparatus

Which reaction does the enzyme phosphoglucose isomerase catalyze? (a) glucose glucose 6-phosphate (b) fructose 6-phosphate fructose 1,6-bisphosphate (c) glucose 6-phosphate fructose 6-phosphate (d) glucose glucose 1-phosphate

Which statement correctly characterizes bound ribosomes? a. Bound ribosomes are enclosed in their own membrane. b. Bound and free ribosomes are structurally different. c. Bound ribosomes generally synthesize membrane proteins and secretory proteins. d. The most common location for bound ribosomes is the cytoplasmic surface of the plasma membrane. e. All of the above.

You are examining a cell line in which activation of the Rho family member Rac promotes lamellipodia formation. Which of the following statements is most likely to be true? (a) Cells carrying a Rac mutation that makes Rac act as if it is always bound to GTP will polymerize more unbranched actin filaments than normal cells. (b) Cells carrying a Rac mutation that makes Rac unable to exchange GDP for GTP will polymerize more unbranched actin filaments than normal cells. (c) Cells carrying a Rac mutation that makes Rac act as if it is always bound to GTP will polymerize more branched actin filaments than normal cells. (d) Cells carrying a Rac mutation that makes Rac unable to exchange GDP for GTP will polymerize more branched actin filaments than normal cells.

You are studying nuclear lamins in yeast. Using recombinant DNA technology, you alter the coding sequence of a nuclear lamin gene such that the gene now codes for a nuclear lamin protein that can no longer be phosphorylated when the nuclear envelope is broken down during mitosis. What do you predict would happen if the yeast cell only had the altered nuclear lamin gene (and not the unaltered version)? (a) Mitosis should proceed as usual because the dephosphorylation of the lamin is what is important for nuclear lamina assembly during mitosis, so phosphorylation will not be necessary. (b) Disassembly of the nuclear lamins will occur prematurely because the lamins cannot be phosphorylated. (c) Nuclear lamins will no longer disassemble properly during mitosis. (d) Nuclear lamins will be unable to produce dimers, as coiled-coil formation will be disrupted

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.

Your intestine is lined with individual cells. No fluids leak between these cells from the gut into your body. Why? a. The intestinal cells are fused together into one giant cell. b. The intestinal cells are bound together by plasmodesmata. c. The intestinal cells are bound together by tight junctions. d. The intestinal cells are bound together by gap junctions. e. The intestinal cells are bound together by the extracellular matrix.

______ ion channels respond to changes in membrane potential. a. Ligand gated b. Stress gated c. Voltage gated

Proteins are transported out of a cell via the _____________ or ___________ pathway. a. endocytic b. endomembrane c. exocytic d. secretory e. Golgi apparatus

c, d

Which of the following apply to the nicotinic acetylcholine receptor? Please select all that apply. a. Binding of acetylcholine to the receptor induces a conformational change that activates a G protein. b. Binding of acetylcholine to the receptor induces a conformational change that opens a transmembrane pore allowing Na+ and Ca2+ to flow into the cell. c. The nicotinic acetylcholine receptor is a pentamer consisting of five integral polypeptides. d. Binding of acetylcholine to the receptor induces a conformational change that opens a transmembrane pore allowing Na+ and K+ to flow into the cell.

c, d

When histone H1 is incorporated into a nucleosome a. the nucleosome is about to be moved by a remodeling enzyme. b. it means that replication of the DNA has just occurred. c. it increases the probability that condensation of the chromatin will occur d. it means that the underlying DNA is probably a core promoter.

c. it increases the probability that condensation of the chromatin will occur

The gas NO can serve as a signal to dilate blood vessels. This is because NO causes an increase in ______________ levels in smooth muscle cells.

cGMP

The α-helical region of therod interacts with the α-helical region of another monomer in a_____________________ configuration to form a dimer.

coiled-coil

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.

consitutive; consitutive; regulated; acidic; do not aggregate

A certain cell has ribosomes and DNA, and is surrounded by a membrane. But there are no mitochondria present. Based on this information, this cell is most likely _____. a. a cell from a pine tree b. a grasshopper cell c. a yeast (fungus) cell d. a bacterium e. The description above could fit any of the cells listed in the answers.

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? Select one: a. The positively charged lysine residues interact with an acidic integral membrane protein. b. The peptide spans the membrane as an α helix. c. The peptide spans the membrane as part of a β sheet. d. The cysteine residue is covalently attached to a membrane lipid.

A hungry yeast cell lands in a car of grape juice and begins to feast on the sugars there, producing carbon dioxide and ethanol in the process. Unfortunately, the grape juice is contaminated with professes that attack some of the transport proteins in the yeast cell membrane, and the yeast cell died. Which of the following could account for the yeast cells demise? a. Toxic buildup of carbon dioxide inside the cell b. Toxic buildup of ethanol inside the cell c. Diffusion of ATP out of the cell d. Inability to import sugar into the cell

Adrenaline stimulates glycogen breakdown in skeletal muscle cells by ultimately activating glycogen phosphorylase, the enzyme that breaks down glycogen, as depicted in Figure Q16-29. Referring to Figure Q16-29, which of the following statements below 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.

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

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

At the end of each phase of cell cycle cyclins activating Cdks in that phase are inactivated irreversibly by (a) Multiple phosphorylations (b) De-phosphorylation (c) Ubiquitinylation (d) Destabilizing by proteolysis in a proteosome

Below is a list of molecules with different chemical characteristics. Knowing that all molecules will eventually diffuse across a phospholipid bilayer, select the option below that most accurately predicts the relative rates of diffusion of these molecules (fastest to slowest). alanine estrogen propanol sodium (a) alanine > propanol > sodium > estrogen (b) sodium > propanol > alanine > estrogen (c) estrogen > propanol > sodium > alanine (d) estrogen > propanol > alanine > sodium

Biologists cannot possibly study all living species. Instead, they try to understand cell behavior by studying a select subset of species. Which of the following characteristics are useful in an organism chosen for use as a model in laboratory studies? a. amenability to genetic manipulation b. ability to grow under controlled conditions c. rapid rate of reproduction d. all of the above

Both excitatory and inhibitory neurons form junctions with muscles. By what mechanism do inhibitory neurotransmitters prevent the postsynaptic cell from firing an action potential? Select one: a. by closing Na+ channels b. by preventing the secretion of excitatory neurotransmitters c. by opening K+ channels d. by opening Cl- channels

Cdk2/cyclinE functions in (a) G2/M transition (b) G2 (c) M (d) G1/S transition

Cell movement involves the coordination of many events in the cell. Which of the following phenomena are not required for cell motility? (a) Myosin-mediated contraction at the rear of the moving cell. (b) Integrin association with the extracellular environment. (c) Nucleation of new actin filaments. (d) Release of Ca2+ from the sarcoplasmic reticulum.

Cell movement involves the coordination of many events in the cell. Which of the following phenomena is not required for cell motility? (a) Myosin-mediated contraction at the rear of the moving cell. (b) Integrin association with the extracellular environment. (c) Nucleation of new actin filaments. (d) Release of Ca2+ from the sarcoplasmic reticulum.

Cells make use of H+ electrochemical gradients in many ways. Which of the following proton transporters is used to regulate pH in animal cells? (a) light-driven pump (b) H+ ATPase (c) H+ symporter (d) Na+-H+ exchanger

Cells of the pancreas will incorporate radioactively labeled amino acids into proteins. This "tagging" of newly synthesized proteins enables a researcher to track their location. In this case, we are tracking an enzyme secreted by pancreatic cells. What is its most likely pathway? a. ER→Golgi→nucleus b. Golgi→ER→lysosome c. nucleus→ER→Golgi d. ER→Golgi→vesicles that fuse with plasma membrane e. ER→lysosomes→vesicles that fuse with plasma membrane

Cholesterol serves several essential functions in mammalian cells. Which of the following is not influenced by cholesterol? (a) membrane permeability (b) membrane fluidity (c) membrane rigidity (d) membrane thickness

Consider the in vitro motility assay using purified kinesin and purified polymerized microtubules shown in Figure Q17-63. The three panels are images taken at 1-second intervals. In this figure, three microtubules have been numbered to make it easy to identify them. Which of the following statements about this assay is false? Figure Q17-63 (a) Kinesin molecules are attached by their tails to a glass slide. (b) The microtubules used in this assay must be polymerized using conditions that stabilize tubule formation or else they would undergo dynamic instability. (c) ATP must be added for this assay to work. (d) Addition of the nonhydrolyzable ATP analog (AMP-PNP) would cause the microtubules to move faster.

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.

Diversity among the oligosaccharide chains found in the carbohydrate coating of the cell surface can be achieved in which of the following ways? Select one: a. varying the types of sugar monomers used b. varying the types of linkages between sugars c. varying the number of branches in the chain d. all of the above

Diversity among the oligosaccharide chains found in the carbohydrate coating of the cell surface can be achieved in which of the following ways? (a) varying the types of sugar monomers used (b) varying the types of linkages between sugars (c) varying the number of branches in the chain (d) all of the above

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

Dye injected into a plant cell might be able to enter an adjacent cell through _____. a. a tight junction b. a microtubule c. a cell wall d. plasmodesmata e. a gap junction

For both actin and microtubule polymerization, nucleotide hydrolysis is important for ______. (a) stabilizing the filaments once they are formed. (b) increasing the rate at which subunits are added to the filaments. (c) promoting nucleation of filaments. (d) decreasing the binding strength between subunits on filaments.

Formation of a lipid bilayer is energetically favorable. How does this arrangement result in higher entropy for the system, and thus make bilayer formation energetically favorable? Select one: a. Fatty acid tails are highly saturated and flexible. b. Hydrogen bonds form between neighboring polar head groups in the bilayer. c. Polar head groups form a hydrogen-bonding network at the interface with water. d. Water molecules form cagelike structures around hydrophobic molecules.

Fully folded proteins typically spontaneously fold into an original conformation. Which of the following statements in FALSE? a. A polar side chain on the outside of a protein can hydrogen bond with water. b. Nonpolar side chains are often packed into a hydrophobic core region. c. A peptide bond is flexible and allows rotation. d. Van der Waals attractions are not strong enough to be present in proteins.

In a DNA double helix, a. the two DNA strands are identical. b. purines pair with purines. c. thymine pairs with cytosine. d. the two DNA strands run antiparallel.

In a centrosome, which structures serve as nucleation sites for the formation of microtubules? (a) Tubulin protofilaments (b) αβ-tubulin dimers (c) α- and β-tubulin monomers (d) gamma-tubulin rings

In a method called patch-clamping, a glass capillary can be converted into a microelectrode that measures the electrical currents across biological membranes. Which of the following is not true about the patch-clamp method? a. The glass capillary adheres to a "patch" of membrane through the application of suction b. The aperture in the glass capillary used to make a microelectrode is about 1μm in diameter. c. If the experimental conditions are held constant, fluctuations in electrical currents across the patch of the membrane are still observed. d. Single-channel patch-clamp recordings have demonstrated that gated membrane channels will only open and close in response to specific stimuli.

In eukaryotic cells the first step in protein synthesis is the _____. a. translation of an RNA nucleotide sequence into a sequence of amino acids b. linking of nucleotides to form a polypeptide c. translation of a DNA nucleotide sequence into a sequence of amino acids d. transferring of information from DNA to messenger RNA e. removal of introns from RNA and the stitching together of exons

In step 2 of the citric acid cycle, the enzyme aconitase generates isocitrate from citrate. Which of the following statements about this reaction is true? (a) There is a substantial free-energy difference between the reactants and products of this reaction. (b) The unbonded electrons from hydroxide ions provide energy for this reaction. (c) The aconitase enzyme functions as a mutase in this reaction. (d) The reaction sequence first generates one molecule of water and then consumes one molecule of water.

K+ leak channels are found in the plasma membrane. These channels open and close in an unregulated, random fashion. What do they accomplish in a resting cell? a. They set the K+ concentration gradient to zero. b. They set the membrane potential to zero. c. They disrupt the resting membrane potential. d. They keep the electrochemical gradient for K+at zero.

Keratins are NOT found in: (a) hair (b) reathers (c) the tongue (d) bones

Keratins, neurofilaments, and vimentins are all categories of intermediate filaments. Which of the following properties is not true of these types of intermediate filaments? (a) They strengthen cells against mechanical stress. (b) Dimers associate by noncovalent bonding to form a tetramer. (c) They are found in the cytoplasm. (d) Phosphorylation causes disassembly during every mitotic cycle.

Microtubules are important for transporting cargo in nerve cell axons, as diagrammed in Figure Q17-33. Notice that the two types of cargo are traveling in opposite directions. Which of the following statements is likely to be false? Figure Q17-33 (a) The gray cargo is attached to dynein. (b) The black cargo and the gray cargo require ATP hydrolysis for their motion. (c) The black cargo moving toward the axon terminal contains a domain that specifically interacts with the tail domain of a particular kind of motor. (d) The black cargo and the gray cargo are moving along microtubules of opposite polarity.

N-linked oligosaccharides are a. Added in the Golgi and modified in the ER b. Added in the cis Golgi and modified in the trans Golgi c. Added in the trans Golgi and modified in secretory vesicles d. Added in the ER and modified in the Golgi

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.

Negatively charged ions are required to balance the net postive charge from metal ions such as K+, Na+, and Ca2+. Which of the following negatively charged ions is the most abundant ourside the cell and which ion does most often neutralize? a. Cl- , Ca2+ b. PO_4^3- , K+ c. PO_4^3- , Ca2+ d. Cl- , Na+

New membrane phospholipids are synthesized by enzymes bound to the _____________side of the _________________ membrane. a. luminal, Golgi b. extracellular, plasma c. cytosolic, mitochondrial d. cytosolic, endoplasmic reticulum

On a diet consisting of nothing but protein, which of the following is the most likely outcome? (a) loss of weight because amino acids cannot be used for the synthesis of fat (b) muscle gain because the amino acids will go directly into building muscle (c) tiredness because amino acids cannot be used to generate energy (d) excretion of more nitrogenous (ammonia-derived) wastes than with a more balanced diet

Plasma membranes are extremely thin and fragile, requiring an extensive support network of fibrous proteins. This network is called the ____________. Select one: a. cytoskeleton b. attachment complex c. spectrin d. cortex

Pyruvate can be converted into many other molecules by various biosynthetic and metabolic pathways, which makes it a central hub in the regulation of cellular metabolism. Which of the following molecules is not made from pyruvate? (a) oxaloacetate (b) ethanol (c) lactate (d) NADH

Pyruvate must move from the cytosol into the mitochondria, where it is oxidized to form CO2 and acetyl CoA by the pyruvate dehydrogenase complex. How many different enzymes and what total number of polypeptides, respectively, are required to perform this oxidation process in the mitochondrion? (a) 1; 60 (b) 3; 3 (c) 3; 26 (d) 3; 60

Red blood cells have been very useful in the study of membranes and the protein components that provide structural support. Which of the following proteins is the principal fibrous protein in the cortex of the red blood cell? (a) tubulin (b) attachment proteins (c) actin (d) spectrin

Several different classes of enzymes are needed for the catabolism of carbohydrates. Which of the following descriptions best matches the function of a kinase? (a) An enzyme that catalyzes the rearrangement of bonds within a single molecule. (b) An enzyme that catalyzes a change in the position of a specific chemical group within a single molecule. (c) An enzyme that catalyzes the oxidation of a molecule by removing a hydride ion. (d) An enzyme that catalyzes the addition of phosphate groups to other molecules.

Some lipases are able to cleave the covalent bonds between the glycerol backbone and the attached fatty acid. What final products do you expect to accumulate through the action of the enzyme monoacylglycerol lipase? Select one: a. sterol and glycerol b. phosphoglycerol and free fatty acid c. free phosphate and glycerol d. glycerol and free fatty acid

Step 3 in glycolysis requires the activity of phosphofructokinase to convert fructose 6-phosphate into fructose 1,6-bisphosphate. Which of the following molecules is an allosteric inhibitor of this enzyme? (a) Pi (b) AMP (c) ADP (d) ATP

The DNA sequence of the template strand for an mRNA gene is 5'CCGGAATT3'. The sequence of the transcript will be ________. a. 5' AATTCCGG 3' b. 5' GGCCAAUU 3' c. 5' CCGGAATT 3' d. 5' AAUUCCGG 3'

The _____ is a selective barrier, regulating the passage of material into and out of the cell. a. lysosome b. nuclear envelope c. chloroplast d. plasma membrane e. nucleus

The citric acid cycle is a series of oxidation reactions that removes carbon atoms from substrates in the form of CO2. Once a molecule of acetyl CoA enters the citric acid cycle, how many complete cycles are required for both of the carbon atoms in its acetyl group to be oxidized to CO2? (a) 1 (b) 2 (c) 3 (d) 4

The complete set of information in an organism's DNA is called its a. inheritance. b. coding sequence. c. gene. d. genome.

The conversion of fructose 1,6-bisphosphate to fructose 6-phosphate is catalyzed by a fructose 1,6-bisphosphatase and is one of the final steps in gluconeogenesis. Which of the following molecules is an allosteric activator of this enzyme? (a) Pi (b) AMP (c) ADP (d) ATP

The correct folding of proteins is necessary to maintain healthy cells and tissues. The presence of unfolded proteins are associated with some neurodegenerative disorders as Alzheimer's disease, Huntington's disease, and Creutzfeldt-Jakob disease (the specific faulty protein is different for each disease). What happens to these disease-causing, unfolded proteins? a. They are degraded. b. They bind a different target protein. c. They form structured filaments. d.They form protein aggregates.

The following statement is consistent with which type(s) of microtubule? "The monomer is sequestered by profilin" (a) cilliary (or flagellar) microtubule (b) mitotic spindle microtubule (c) both a and b (d) none of the above

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? a. 22 b. 23 c. 44 d. 46

The hydrolysis of GTP to GDP carried out by tubulin molecules ________________. (a) provides the energy needed for tubulin to polymerize. (b) occurs because the pool of free GDP has run out. (c) tips the balance in favor of microtubule assembly. (d) allows the behavior of microtubules called dynamic instability

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.

The oxygen-dependent reactions required for cellular respiration were originally thought to occur in a linear pathway. By using a competitive inhibitor for one enzyme in the pathway, investigators discovered that these reactions occur in a cycle. Which enzyme was inhibited? (a) aconitase (b) isocitrate dehydrogenase (c) malate dehydrogenase (d) succinate dehydrogenase

The primary role of _____ is to bind animal cells together. a. plasmodesmata b. gap (communicating) junctions c. the cytoskeleton d. desmosomes e. tight junctions

The stimulation of auditory nerves depends on the opening and closing of channels in the auditory hair cells. Which type of gating mechanism do these cells use? a. voltage-gated b. extracellular ligand-gated c. intracellular ligand-gated d. stress-gated

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) a. 24 carbons with 1 double bond b. 20 carbons with 2 double bonds c. 16 carbons with no double bonds d. 15 carbons with 2 double bonds

Ubiquitin is a (a) Protein kinase (b) Protease (c) Component of the electron transport system (d) Protein that tags another protein for proteolysis

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

Water molecules readily form hydrogen bonds with other polar molecules, and when they encounter nonpolar molecules they must form hydrogen-bonding networks withneighboring water molecules. Which of the following molecules will cause a "cage" of water to form? Select one: a. acetone b. methanol c. urea d. 2-methylpropane

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

Which of the following chemical groups is NOT used to construct a DNA molecule? a. five-carbon deoxyribose sugar b. phosphate c. nitrogen-containing base d. six-carbon ribose sugar

Which of the following choices reflects the appropriate order 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

Which of the following has an antagonistic action to adenylate cyclase? a. Cyclic adenosine monophosphate (cAMP) b. Protein kinase c. The active GTP-α subunit of a G protein d. Phosphodiesterase

Which of the following is required for the secretion of neurotransmitters in response to an action potential? Select one: a. neurotransmitter receptors b. Na+-K+ pumps c. voltage-gated K+ channels d. voltage-gated Ca2+ channels

Which of the following membrane lipids does not contain a fatty acid tail? a. phosphatidylcholine b. a glycolipid c. phosphatidylserine d. cholesterol

Which of the following membrane lipids does not contain a fatty acid tail? (a) Phosphatidylcholine (b) A glycolipid (c) Phosphatidylserine (d) Cholesterol

Which of the following negatively charged ions is the most abundant outside the cell and which ion does most often neutralize? a. Cl- (Ca2+) b. PO4^3- (K+) c. PO4^3- (Ca2+) d. Cl- (Na+)

Which of the following occurs in meiosis but not in mitosis? (a) Attachment of spindle fibers to kinetochore (b) Replication of DNA prior to start of cell division (c) Separation of sister chromatids at anaphase (d) Pairing of homologous chromosomes at metaphase plate

Which of the following processes do not take place in the mitochondria? (a) citric acid cycle (b) conversion of pyruvate to activated acetyl groups (c) oxidation of fatty acids to acetyl CoA (d) glycogen breakdown

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

Which of the following stages in the breakdown of the piece of toast you had for breakfast generates the most ATP? a. the digestion of starch to glucose b. glycolysis c. the citric acid cycle d. oxidative phosphorylation

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 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.

Which of the following statements about actin is false? (a) ATP hydrolysis decreases actin filament stability. (b) Actin at the cell cortex helps govern the shape of the plasma membrane. (c) Actin filaments are nucleated at the side of existing actin filaments in lamellipodia. (d) The dynamic instability of actin filaments is important for cell movement.

Which of the following statements about the cytoskeleton is true? (a) All eukaryotic cells have actin, microtubules, and intermediate filaments in their 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 about the structure of microtubules is false? (a) Microtubules are built from protofilaments that come together to make a hollow structure. (b) The two ends of a protofilament are chemically distinct, with α-tubulin exposed at one end and β-tubulin exposed at the other end. (c) Within a microtubule, all protofilaments are arranged in the same orientation, giving the microtubule structural polarity. (d) α-Tubulin and β-tubulin are covalently bound to make the tubulin dimer that then assembles into protofilaments

Which of the following statements does not accurately describe the events involved in the propagation of an action potential? a. an initial influx of Na+ through a small cluster of channels causes local depolarization of the membrane b. local depolarization causes nearby Na+ channels to open c. Channels in depolarized regions of the membrane are inactivated until the resting membrane potential is reestablished d. the opening of transmitter-gated K+ channels helps repolarize the membrane

Which of the following statements is FALSE? a. A new RNA molecule can begin to be synthesized from a gene before the previous RNA molecule's synthesis is completed. b. If two genes are to be expressed in a cell, these two genes can be transcribed with different efficiencies. c. RNA polymerase is responsible for catalyzing the formation of the phosphodiester bonds between nucleotides. d. Unlike DNA, RNA uses a uracil base and a deoxyribose sugar.

Which of the following statements is correct? a. Coatomer-coated II transition vesicles bud from transitional endoplasmic reticulum and eventually fuse with the trans Golgi network. b. With reference to coated vesicles, COP refers to clathrin coated vesicles. c. The G protein, guanine nucleotide exchange factor mediates the formation of endoplasmic reticulum-derived COP vesicles. d. Active ADP ribosylation factor (ARF-GTP) binds to the endoplasmic reticulum membrane and recruits coatomer proteins to the site of vesicle formation.

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

Which of the following statements is true? a. Amoebae have transporter proteins that actively pump water molecules from the cytoplasm to the cell exterior. b. Bacteria and animal cells rely on the Na+-K+pump in the plasma membrane to prevent lysis resulting from osmotic imbalances. c. The Na+-K+ pump allows animal cells to thrive under conditions of very low ionic strength. d. The Na+-K+ pump helps to keep both Na+ and Cl- ions out of the cell.

Which of the following statements regarding cyclins is not correct? (a) They can become linked to ubiquitin (b) They catalyze the phosphorylation of protein (c) They contain specific amino acid sequence that target them for proteolysis (d) They are activated and degraded during cell cycle

Which of the following statements regarding dynamic instability is false? (a) Each microtubule filament grows and shrinks independently of its neighbors. (b) The GTP cap helps protect a growing microtubule from depolymerization. (c) GTP hydrolysis by the tubulin dimer promotes microtubule shrinking. (d) The newly freed tubulin dimers from a shrinking microtubule can be immediately captured by growing microtubules and added to their plus end.

Which of the statements below about intermediate filaments is false? (a) They can stay intact in cells treated with concentrated salt solutions. (b) They can be found in the cytoplasm and the nucleus. (c) They can be anchored to the plasma membrane at a cell-cell junction. (d) Each filament is about 10 µm in diameter

Which one of the statements below about intermediate filaments is false? (a) They can stay intact in cells treated with concentrated salt solutions. (b) They can be found in the cytoplasm and the nucleus. (c) They can be anchored to the plasma membrane at cell-cell junction. (d) Each filament is about 10 μm in diameter.

Which structure is common to plant and animal cells? a. chloroplast b. wall made of cellulose c. central vacuole d. mitochondrion e. centriole

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.

You are interested in understanding the regulation of nuclear lamina assembly. To create an in vitro system for studying this process you start with partly purified nuclear lamina subunits to which you will add back purified cellular components to drive nuclear lamina assembly. Before you start doing experiments, your instructor suggests that you consider what type of conditions would be most amenable to the assembly of the nuclear lamina from its individual subunits in vitro. Which of the following conditions do you predict would be most likely to enhance the assembly of the nuclear lamina? (a) addition of phosphatase inhibitors (b) addition of ATP (c) addition of a concentrated salt solution that is 10 times the concentration normally found in the nucleoplasm (d) addition of protein kinase inhibitors

Your friend works in a biotech company that has just discovered a drug that seems to promote lamellipodia formation in cells. Which of the following molecules is unlikely to be involved in the pathway that this drug affects? (a) Rac (b) ARP (c) actin (d) myosin

These filaments are usually connected from cell to cell through junctions called __________________.

desmosomes

The motor protein __________________ generates the bending motion in cilia; the lack of this protein can cause Kartagener's syndrome in humans.

dynein

A substance moving from outside the cell into the cytoplasm must pass through _____. a. a microtubule b. several different organelle membranes c. a ribosome d. the nucleus e. the plasma membrane

Which of the following are possible sites of protein synthesis in a typical eukaryotic cell? a. the cytoplasm b. the rough endoplasmic reticulum c. in mitochondria d. The first two answers are correct. e. The first three answers are correct

Which of the following is a possible reason for grouping the peroxisomes with chloroplasts and mitochondria? a. They are all involved in ATP synthesis. b. They all contain two or more membranes. c. They all contain DNA and make some of their own proteins. d. They are all part of the plastid family of organelles. e. None of these organelles are part of the endomembrane system.

Which of these is involved in the manufacture of membrane? a. smooth endoplasmic reticulum b. ribosomes c. Golgi apparatus d. nucleolus e. rough endoplasmic reticulum

Which of these organelles produces H2O2 as a by-product? a. mitochondrion b. nucleus c. centrioles d. flagellum e. peroxisome

_____ are the sites of protein synthesis. a. Mitochondria b. Peroxisomes c. Golgi apparatuses d. Microfilaments e. Ribosomes

_____ is/are identical in structure to centrioles. a. Mitochondria b. Nuclear envelopes c. Chromatin d. Microfilaments e. Basal bodies

______________ strands of tetramers come together and twist together to form the _________________ nm filament.

eight, ten

When the hormone, insulin, is released into the bloodstream, what form of cell-to-cell signaling is being used?

endocrine

How might prions be absorbed from the intestines?

endocytosis

The ___________________ domains are exposed on the surface of theintermediate filament, allowing for interaction with cytoplasmic components.

globular

Intermediate filaments are elongated fibrous proteins with an N-terminal globular_________________ region and a C-terminal globular _________________region; these regions flank the elongated rod domain.

head, tail

K+ concentration is higher inside/outside the cell?

inside

__________ include keratin and neurofilaments.

intermediate filaments

__________ support and strengthen the nuclear envelope.

intermediate filaments

___________ can be connected through desmosomes.

intermediate filaments

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. 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. Macrophages are especially suited for this process, as they extend __________________ (sheetlike projections of their plasma membrane) to surround the invading microorganisms. a. chaperone b. golgi apparatus c. pseudopods d. cholesterol e. mycobacterium f. rough ER g. clathrin h. phagocytosis i. SNARE j. endosome k. pinocytosis l. transcytosis

k, g, j, h, c

For example, the skin of people with epidermolysis bullosa simplex is very susceptible to mechanical injury; people with this disorder have mutations in their __________________ genes, which code for the intermediate filament found in epithelial cells.

keratin

Proteins are transported out of a cell via the ____________ or _________ pathway. Fluids and macromolecules are transported into the cell via the ______________ pathway. All proteins being transported out of the cell pass through the _____________ and the ______________. Transport vesicles link organelles of the _______________ system. The formation of _____________ in the endoplasmic reticulum stabilizes protein structure. a. carbohydrate b. Golgi apparatus c. disulfide bonds d. hydrogen bonds e. endocytic f. ionic bonds g. endomembrane h. lysosome i. endoplasmic reticulum j. protein k. endosome l. secretory m. exocytic

l, m, e, i, b, g, c

Humans with progeria, adisease that causes premature aging, carry mutations in a nuclear ____________.

lamin

__________ are composed of a monomer that binds ATP.

microfilaments

__________ are important for formation of the contractile ring during cytokinesis.

microfilaments

___________ are abundant in filopodia.

microfilaments

___________ are directly involved in muscle contraction.

microfilaments

The stability of __________ involves a GTP cap.

microtubules

___________ are components of the mitotic spindle.

microtubules

___________ are used in the eucaryotic flagellum.

microtubules

Ca2+ concentration is higher inside/outside the cell?

outside

Cl- concentration is higher inside/outside the cell?

outside

Mg2+ concentration is higher inside/outside the cell?

outside

Na+ concentration is higher inside/outside of cell?

outside

Many of the extracellular signal molecules that regulate inflammation are released locally at the site of infection. What form of cell-to-cell signaling is being used?

paracrine

Glucose from intestine to bloodstream is what type of transport?

passive

eukaryotic cells are continually taking up materials from the extracellular space by the process of endocytosis. One type of endocytosis is _____ which uses _______ a coat protein, to form small vesicles containing fluids and molecules. After these vesicles have pinched off from the plasma membrane they will fuse with the ______ where materials that are taken into vesicle are sorted. A second type of endocytosis is _____ which is used to take up large vesicles that can contain microorganisms and cellular debris.

pinocytosis, CLATrin, endosomes, phagpcytosis

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

pinocytosis, clathrin, endosome, phagocytosis, pseudopods

People who carry mutations in the gene for __________________, an important protein for cross-linking intermediate filaments, have a disease that combines symptoms of epidermolysis bullosa simplex, muscular dystrophy, and neurodegeneration.

plectin

Name three possible fates for an endocytosed molecule that has reached the endosome

recycling, degradation, transcytosis

______________dimers will line up to form a staggered tetramer.

two

The main filaments found in muscle cells belong to the __________________ family; people with disruptions in these intermediate filaments can have muscular dystrophy. In the nervous system, __________________ help strengthen the extremely long extensions often present in nerve cell axons; disruptions in these intermediate filaments can lead to neurodegeneration.

vimentin, neurofilaments

__________________ rings are important for microtubulenucleation and are found in the __________________ , which is usually foundnear the cell's nucleus in cells that are not undergoing mitosis.

y-tubulin, centrosome

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