Cell Theory Midterm 2
The major products of the citric acid cycle are a) CO2 and NADH. b) NADH and ATP. c) H2O and ATP. d) pyruvate and ATP.
A
The slow rise of S cyclin levels throughout G1 phase is due to ___________, and the abrupt decrease is caused by ___________. a) transcription; proteolysis b) phosphorylation; translation c) synthesis; mitosis d) import; export
A
What drives the reassembly of the nuclear envelope? a) dephosphorylation of lamins b) destruction of cohesin c) invagination of the ER membrane d) expression of all new lamin proteins
A
The contractile ring is composed of a) tubulin and dynein. b) actin and myosin. c) tubulin and kinesin. d) keratin fibers.
B
(Q009) Which of the following accurately describes a step in GTP-driven nuclear transport?
Binding of Ran-GTP to the receptor releases the cargo protein
A cell membrane made up primarily of lipids with which characteristics would be the least fluid (i.e., most stiff)? a. short, saturated fatty acid tails b. long, unsaturated fatty acid tails c. long, saturated fatty acid tails d. short, unsaturated fatty acid tails
Long sat.
A less permeable membrane is likely to have a. less cholesterol. b. shorter fatty acid tails. c. more cholesterol. d. many unsaturated fatty acids.
More cholesterol
A ___________ is a long structure found in abundance in the cytoplasm of a single skeletal muscle fiber, and is composed of many bundles of actin and myosin filaments that are arranged in repeating units. a. thick filament b. myofibril c. sarcomere d. contractile ring
Myofibril
(Q017) What is one of the main differences in the behavior of the proteins in a vesicle destined for constitutive secretion, and the proteins in the vesicle destined for regulated secretion?
Proteins in the regulated secretion vesicle tend to aggregate and become highly concentrated in the ionic conditions in the vesicle.
(Q015) Which of the following is a covalent modification that occurs mainly in the ER?
formation of disulfide bonds
(Q005) Which of the following compartments receives proteins directly from cytosol?
peroxisomes, mitochondria, nucleus, chloroplasts
The end of the microtubule that has /alpha-tubulin exposed is the a. (+) end. b. Neither end has /alpha-tubulin exposed. c. (-) end. d. Both (+) and (-) ends.
(-) end
(Q003) Approximately what percentage of the volume of a typical eukaryotic cell is comprised of cytosol?
50%
How are spindle microtubules attached to chromosomes? Group of answer choices a) The microtubules bind to the kinetochore complexes through a connecting protein. b) The plus ends of the microtubules bind directly to DNA. c) The minus ends of the microtubules bind directly to a protein complex on DNA. d) The microtubules bind to cohesion complexes on the DNA.
A
How does S-Cdk prevent re-replication? degradation of DNA polymerase a) phosphorylation of ORC and Cdc6 b) inactivation of G1-Cdk c) activation of helicases to denature DNA
A
If Ras contains a mutation that leads to a defect in GTP hydrolysis, this could fuel uncontrolled proliferation in cancer because Select one: a.Ras is able to signal to downstream pathways inappropriately. b.Ras is unable to send signals to downstream pathways. c.Ras is unable to bind to the GEF for activation. d.Ras is able to migrate to the nucleus and deactivate transcription of proliferation genes.
A
In response to an apoptotic stimulus, initiator caspases a) cleave and activate executioner caspases. b) degrade procaspases. c) cleave a transcription factor to active gene expression. d) degrade executioner caspases.
A
Shown below is a diagram of how theoretical intracellular signaling pathways could integrate incoming signals to produce a coordinated cell response.Which signal(s) would lead to activation of both kinase 1 and kinase 2? Select one: a. signals A and D b. signal C c. signals C and D d. signals A and C
A
Stage two of photosynthesis (or the light-independent reactions) uses which input molecules to produce organic food molecules? Group of answer choices a) ATP, NADPH, CO2 b) amino acids, sugars, fatty acids c) O2, NADH, ADP d) H2O, light, chlorophyll
A
The active form of a monomeric GTP-binding protein is the Select one: a.GTP-bound form. b.GDP-bound form. c.guanine nucleotide exchange factor (GEF). d.GTPase-activating protein (GAP).
A
The expression levels of different ___________ fluctuate throughout the cell cycle. a) cyclins b) Cdks c) phosphates d) cyclins and Cdks
A
The first step in a signaling pathway that responds to a molecule that stays in the extracellular space is Select one: a.binding of the signal molecule to a receptor. b.diffusion through the plasma membrane into the cell. c.activation of gene expression. d.phosphorylation and activation of the receptor protein.
A
What accounts for the difference in the curve shapes depicting concentration of M-cyclin versus M-Cdk activity during the cell cycle? a) The M-Cdk complex is not activated until M-cyclin is bound and M-Cdk is dephosphorylated. b) The M-Cdk complex is not activated until M-cyclin is fully bound. c) The M-Cdk activity levels reach their peak slowly due to the time required for synthesis of the proteins. d) The M-Cdk complex is not activated until it is dephosphorylated in mitosis.
A
When activated, a G-protein has a structure that Select one: a.is bound to GTP. b.forms a complete complex with three subunits. c.forms a transmembrane domain. d.is able to bind to extracellular signals.
A
Which cAMP-mediated signaling pathway would take on the order of minutes to hours for a response to develop (as opposed to seconds)? Select one: a.a response where cAMP leads to the activation of a transcriptional regulator b.a response where cAMP leads to the activation of a biosynthetic enzyme c.a response where cAMP leads to the activation of a catabolic enzyme d.a response where cAMP leads to the release of calcium ions from the ER
A
Which of the following correctly matches the phase of the eukaryotic cell cycle with an event that takes place in that phase? a) M phase—cytokinesis b) S phase—cell growth c) G2 phase—mitosis d) G1 phase—DNA synthesis
A
Detergent molecules are ___________ in nature and bind with membrane proteins and membrane lipids to disrupt their interactions and release the proteins from the membrane. a. amphipathic b. hydrophobic c. hydrophilic d. polar
AaaaA
At the leading edge of a cell, ARP proteins help form new branches on actin filaments to push the leading edge forward using the force of the polymerization, as shown in the figure below. ECB5_CP_1703 Click to view larger image. a. at the plus ends of newly polymerized actin filaments b. in branches off of existing actin filaments c. at the minus ends of depolymerizing actin filaments d. from the capped ends of actin filaments
At the plus ends of newly polymerized actin filaments
Cohesin is cleaved by the enzyme ___________, which is held in an inactive state by ___________ until it is degraded by the APC/C complex. a) nuclease; securin b) separase; securin c) securin; separase d) separase; kinetochores
B
Enzymes that add a phosphate group to a switch protein are called Select one: a.phosphatases. b.kinases. c.GTPases. d.G-proteins.
B
How does the binding of a signal molecule activate an RTK for downstream signaling? Select one: a.The RTK changes conformation to stimulate a G-protein. b.The RTK forms a dimer and cross-phosphorylates itself. c.The RTK undergoes a cleavage event to release the cytosolic portion. d.The RTK is an ion channel that opens in response to ligand binding.
B
Steroid hormones trigger transcription of target genes by Select one: a.binding directly to DNA and stimulating transcription. b.binding to nuclear receptors that act as transcription factors for specific genes. c.activating a kinase cascade that results in the activation of a transcription factor for a set of genes. d.activating the release of Ca+2 ions that bind to and activate transcription factors.
B
What can happen if heterochromatin spreads inappropriately into an area with active genes? a) The region will convert into a telomere. b) The active genes can become silenced. c) Heterochromatin cannot spread into areas with active genes. d) The genes will resist and remain active.
B
What type of cell response would take the longest amount of time (on the scale of minutes to hours) to execute? Select one: a.one that involves the release of secretory vesicles b.one that involves a change in gene expression c.one that involves the firing of an action potential along a neuron d.one that uses a phosphorylation event to activate an enzyme
B
Which is NOT a transition point where the cell cycle control system regulates progression through the cell cycle? chromosome segregation a) G1/S transition b) S/G2 transition c) G2/M transition
B
Which of the following choices reflects the appropriate order of locations through which a protein destined for the plasma membrane travels? a) ER ⟶ lysosome ⟶plasma membrane b) ER ⟶ Golgi ⟶plasma membrane c) lysosome ⟶endosome ⟶plasma membrane d) Golgi ⟶ lysosome ⟶plasma membrane
B
Which of the following correctly matches a G-protein-activated enzyme with the second messenger molecule it produces? Select one: a.adenylyl cyclase → inositol triphosphate b.phospholipase C → diacylglycerol c.guanylyl cyclase → GTP d.protein kinase A → Ca2+
B
Which of the following is a common transmembrane protein structure that can traverse the membrane to form a pore or channel by alternating hydrophobic and hydrophilic amino acids? a. single-pass alpha helix b. multipass alpha helix c. beta barrel d. beta sheet
BDetergent molecules are ___________ in nature and bind with membrane proteins and membrane lipids to disrupt their interactions and release the proteins from the membrane. a. amphipathic b. hydrophobic c. hydrophilic d. polar
Microtubules extend from organizing centers in the cell. Which is an example of an organizing center? a. basal body of a cilium b. nuclear periphery c. centromere of a chromosome d. vesicle membrane
Basal body
Microtubules participate in the spatial polarization of nerve cells because a. microtubules are only located in the nerve cell body. b. microtubules extend through the axon with (-) ends toward the terminal and bind vesicles there. c. microtubules have no polarity. d. microtubule (-) ends originate near the cell body allowing (+) end-directed transport along the axon.
Microtubules (-) ends originate near the cell body allowing (+) end-directed transport along the axon
Which of the following motor proteins has one head domain, moves along actin toward the plus end, and is found in all cell types? a. myosin-II b. cytoplasmic dynein c. kinesin d. myosin-I
Myosin-I
Taxol and colchicine are used to treat cancer because they arrest dividing cells in mitosis. What is the mechanism of action of these drugs? a. Both drugs stabilize microtubules. b. Both drugs destabilize microtubules. c. Both drugs constrain the dynamic instability of microtubules. d. Taxol prevents polymerization of microtubules, colchicine prevents disassembly of microtubules.
Both drugs constrain the dynamic instability of microtubules
Which motor protein is an ATPase, has two globular heads, moves toward the (-) end of a microtubule, and generally interacts with cargo via an adaptor protein? a. myosin-I b. kinesin c. myosin-II d. cytoplasmic dynein
Cytoplasmic dynein
Calcium ion release triggers all of the following biological processes EXCEPT Select one: a.muscle contraction. b.fertilized egg development. c.secretion of neurotransmitters. d.action potential transmission along an axon.
D
Consider an animal cell that has eight chromosomes (four pairs of homologous chromosomes) in G1 phase. This cell has _________sister chromatids and _________ centrioles. a) 8, 2 b) 16, 2 c) 8, 4 d) 16, 4
D
If a chromosome is attached to two microtubules from opposite poles and one of the microtubules is experimentally severed, what occurs? a) The chromosome remains aligned along the equator of the metaphase spindle. b) The severed microtubule immediately regenerates and reattaches. c) The remaining microtubule releases the chromosome contacts. d) The chromosome migrates quickly to the pole to which it is still attached.
D
The figure below shows some steps involved in the initiation of DNA replication. What is the identity of the complex labeled "B"? a) DNA polymerase b) Cdc6 c) pre-replication complex d) ORC
D
The genes in the genome of an adult organism. a) must all be expressed in all cells of the organism for survival. b) are vastly different in composition depending on the cell type. c) are mostly silenced after embryonic development is complete. d) are expressed or silenced depending on whether a gene is needed in that cell type and environment.
D
What is the function of condensins? Group of answer choices a) to hold sister chromatids together b) to shorten the contractile ring c) to break down the nuclear envelope d) to coil sister chromatids into a compact form
D
Which of the following correctly matches the cellular location with the production of ATP by oxidative phosphorylation in that cell type? a) chloroplasts—plants b) cell wall—photosynthetic algae c) mitochondria—archaea d) plasma membrane—bacteria
D
Which of the following types of cell signaling is long range and uses hormones as signals? Select one: a.paracrine b.neuronal c.contact-dependent d.endocrine
D
Why do cells regulate their membrane fluidity? a. so they don't freeze in cold temperatures b. so that large, charged molecules can easily pass through the membrane c. to keep two neighboring cells from easily fusing d. to allow membrane proteins to diffuse to where they are needed for their function
D
Which type of movement is the least common for lipids in a bilayer? ECB5_CP_1102 Click to view larger image. a. flip-flop b. lateral diffusion c. flexion d. rotation
Flip flop
(Q002) Which of the following organelles is surrounded by a single membrane?
Golgi apparatus
Phospholipids assemble into in a membrane using a. assembly proteins. b. covalent bonds. c. enzymes. d. hydrophobic forces.
Hydrophobic forces
In terms of structure, if cytoplasmic intermediate filaments are described as ropes, nuclear lamins could be best described as a. mesh. b. string. c. glass. d. wood.
Mesh
Which of these macromolecules is NOT commonly found in the plasma membrane? a. nucleic acids b. fatty acids c. proteins d. carbohydrates
Nucleic acids
Proteins that are associated with the membrane by noncovalent interactions with other membrane proteins are called ___________ proteins. a. peripheral membrane b. lipid-linked c. integral membrane d. monolayer-associated
Peripheral
Which of the following actin-binding proteins prevent polymerization of actin monomers? a. formins and profilin b. thymosin and ARPs c. formins and ARPs d. thymosin and profilin
Thymosin and profilin
Plasma membrane proteins that move ions in and out of cells using active transport are called a. channels. b. transporters. c. receptors. d. anchors.
Transporters
(Q011) A single-pass transmembrane protein destined for one of the organelles in the endomembrane system would be marked by what type of signal sequence?
a cleaved N-terminal ER signal sequence and an internal stop-transfer sequence
(Q010) Proteins encoded by nuclear genes and destined for the mitochondrial matrix are
in possession of a signal sequence for targeting to the mitochondria
(Q004) Which of the following organelles is NOT a part of the endomembrane system?
nucleus
(Q007) Fully folded proteins can be transported into which of the following organelles?
nucleus
(Q020) Lysosomes contain ____________ enzymes that can break down diverse macromolecules, cell parts, and microorganisms.
hydrolytic
(Q018) Which of the endocytic pathways involves the ingestion of large particles or microorganisms and is performed mainly by specialized cells?
phagocytosis
Which of the following depicts the correct order of steps involved in nitric oxide (NO) signaling to trigger smooth muscle relaxation? Select one: a.acetylcholine receptor activation → activation of NO synthetase → NO diffusion into neighboring cells → activation of guanylyl cyclase → cGMP production b.receptor tyrosine kinase activation → activation of protein kinase A → activation of guanylyl cyclase c.activation of guanylyl cyclase → cGMP production → activation of NO synthetase → NO diffusion into neighboring cells d.acetylcholine receptor activation → activation of guanylyl cyclase → activation of NO synthetase → NO diffusion into neighboring cells → cGMP production
A
Which of the following describes negative feedback regulation? Select one: a.A component late in the pathway inhibits an enzyme early in the pathway. b.A component acts to further activate the signaling pathway and enhance the cell's response. c.A component generates an all-or-none, switch-like mechanism. d.A component amplifies the signal for a more robust response.
A
Which type of noncovalent interaction can involve either the polypeptide backbone or amino acid side chains? a) hydrogen bonds b) electrostatic interactions c) van der Waals attractions d) hydrophobic forces
A
________ are the most abundant molecules in the animal cell membrane, whereas ________ make up 50% of the membrane by mass. a. Proteins, lipids b. Lipids, carbohydrates c. Lipids, proteins d. Carbohydrates, lipids
A Plasma membrane proteins that move ions in and out of cells using active transport are called a. channels. b. transporters. c. receptors. d. anchors.
In a famous experiment, mouse cells and human cells were fused into hybrid cells and the membrane proteins of human origin and mouse origin were specifically tagged and examined. After cell fusion and incubation, what was observed by investigators? a. The mouse and human proteins mixed evenly throughout the membrane of the hybrid cell. b. The human proteins mixed throughout the membrane of the hybrid cell, whereas the mouse proteins remained in half of the membrane, in their original location. c. The mouse and human proteins remained separated from each other on opposite sides of the hybrid cell. d. The mouse proteins mixed throughout the membrane of the hybrid cell, whereas the human proteins remained in half of the membrane, in their original location.
Aaaaaaaaaasaaaa
When an action potential excites a muscle cell, where do the calcium ions come from? a. the sarcoplasmic reticulum b. the extracellular space c. the calcium secretory vesicles d. both the extracellular space and the sarcoplasmic reticulum
Both the extracellular space and the sarcoplasmic reticulum
If a phospholipid is located in the outer layer of the bilayer in a vesicle, where will it end up when the vesicle fuses with the plasma membrane? a. Vesicles cannot fuse with the plasma membrane. b. the cytosolic face of the bilayer c. randomly on one side or another d. the extracellular face the bilayer
Bwhat
Excess amounts of the amino acid tryptophan result in downregulation of the expression of the enzymes required for its synthesis due to a) the inability of the repressor to bind to the operator. b) inactivation of the repressor protein. c) the repressor binding to the operator. d) the inactivation of RNA polymerase.
C
If the backbone of a polypeptide is hydrophilic, how can a transmembrane alpha helix span the hydrophobic portion of the lipid bilayer? a. because the membrane bends in such a way that the polar heads of the lipids contact the transmembrane helix b. because many transmembrane alpha helices must come together in a way that neutralizes the hydrophilic backbone c. because amino acid side chains in a transmembrane helix are hydrophobic and interact with the hydrophobic interior of the bilayer d. because the hydrophilic backbone makes a hole in the membrane
C
In which phase of mitosis does the nuclear envelope break down? Group of answer choices a) metaphase b) prophase c) prometaphase d) anaphase
C
Lysosomes and peroxisomes both perform a series of reactions to break down molecules, but one difference between them is that a) peroxisomes digest molecules for reuse. b) lysosomes are large and form an interconnected network. c) peroxisomes contain hydrogen peroxide. d) lysosomes break down toxic molecules.
C
M-Cdk is suddenly activated at the end of G2 by Group of answer choices a) destruction of cyclins. b) activation of APC/C. c) dephosphorylation by Cdc25. d) phosphorylation by Wee1.
C
One of the two types of GTP-binding proteins, often called G-proteins, are membrane bound. These are the Select one: a.monomeric GTP-binding proteins. b.cyclic GMPs. c.trimeric GTP-binding proteins. d.G-protein coupled receptors.
C
Shown is a schematic of the light-induced signaling cascade in rod photoreceptor cells. At which step does the response become amplified so that one photon stimulates a multifaceted response? Select one: a. G-proteins activating cyclic GMP phosphodiesterase b. cGMP hydrolysis leading to the closing of cation channels c. cyclic GMP phosphodiesterase hydrolyzing cGMP molecules d. action potential propagation down the nerve axon
C
The sigma subunit of bacterial RNA polymerase ___________________. Group of answer choices a) contains the catalytic activity of the polymerase. b) remains part of the polymerase throughout transcription. c) recognizes promoter sites in the DNA. d) recognizes transcription termination sites in the DNA.
C
What is the function of cohesins? a) to shorten the contractile ring b) to break down the nuclear envelope c) hold two sister chromatids together during replication.
C
Which of the following is NOT an intracellular signaling protein activated by an RTK? Select one: a.Ras b.monomeric GTPase c.G-protein d.PI-3-kinase
C
Which of the following would produce the fastest response to G-protein activation? Select one: a.cyclic AMP production b.cyclic GMP production c.ion channel activation d.production of inositol triphosphate
C
Which type of cell-surface receptor(s), when activated, catalyze(s) a reaction inside the cell? Select one: a.ion-channel-coupled receptors b.G-protein-coupled receptors c.enzyme-coupled receptors d.enzyme-coupled receptors AND G-protein-coupled receptors
C
How is muscle contraction reversed? a. Calcium ion pumps in the sarcoplasmic reticulum reduce the cytosolic calcium levels and tropomyosin blocks the myosin binding site on actin. b. Calcium is pumped out of the cell to reverse the voltage and cause myosin to degrade. c. Calcium is neutralized by an influx of negatively charged ions, which block calcium from binding to myosin. d. Calcium binds to calmodulin and is quickly degraded to relieve calcium's inhibition of tropomyosin.
Calcium ion pumps in the sarcoplasmic reticulum reduce the cytosolic calcium levels and tropomyosin blocks the myosin binding site on actin
How do calcium ions stimulate contraction in nonmuscle cells and smooth muscle cells? a. Calcium ions lead to activation of a kinase that phosphorylates nonmuscle myosin to alter its conformation and enable actin binding. b. Calcium ions bind to troponin and lead to a conformational change in tropomyosin that exposes the myosin binding sites on the actin filament. c. Calcium ions released into the cell promote the release of secretory vesicles that send neurotransmitters to neighboring cells to stimulate an action potential. d. Calcium ions trigger an action potential in the cell, leading to gene expression changes that influence contraction.
Calcium ions bind to troponin and lead to a conformational change in tropomyosin that exposes the myosin binding sites on the actin filament.
(Q013) How do clathrin-coated vesicles select their cargo molecules?
Cargo receptors bind specifically to cargo proteins and to clathrin
(Q016) How are misfolded proteins and incompletely assembled proteins retained in the ER?
Chaperone proteins bind them and prevent their entry into vesicles.
(Q006) What would the final destination be for a protein bearing both an ER sorting signal and a nuclear localization signal?
ER
Where are new phospholipids made? a. nucleus b. Golgi apparatus c. mitochondria d. endoplasmic reticulum
Er
(Q012) Which of the following is a difference between exocytic and endocytic pathways?
Exocytic pathways often start with synthesis of proteins, whereas endocytic pathways involve breaking down macromolecules like proteins.
Which of the cytoskeletal structures are made up of protein subunits that are fibrous? a. actin filaments b. microtubules c. None. All of the protein subunits that make up cytoskeletal structures are globular. d. intermediate filaments
Intermediate filaments
Microtubules are made up of 13 ___________ that are linear chains of ___________. a. microfilaments; tubulin rings b. tubulin dimers; protofilaments c. tubulin rings; microfilaments d. protofilaments; tubulin dimers
Protofilaments and tubulin dimers
Which of the following is an important function of intermediate filaments? a. providing tensile strength to the cell and the nucleus b. forming attachments for cells to move along a substrate c. moving vesicles from location to location in the cell d. separating chromosomes during mitosis
Providing tensile strength to the cell and the nucleus
The binding of ATP causes a conformational change in myosin that a. releases the myosin head from the actin filament. b. moves the myosin head one step forward on the actin filament. c. move the actin filament in a force-generating "power stroke." d. attaches the myosin head to the actin filament.
Releases the myosin head from the actin filament
A phospholipid is inserted into the cytosolic side of the ER membrane. Which of the following could randomly reposition this phospholipid to the other (lumen) side of the ER membrane? a. glycolipids b. Golgi apparatus c. flippase d. scramblase
Scramblase
Microtubules are inherently unstable unless they are a. able to bind GTP. b. bound to kinesin. c. assembled in the nucleus. d. stabilized by a (+) end attachment.
Stabilized by a (+) end attachment
How do the intermediate filament proteins keratin, vimentin, and neurofilaments differ from each other? a. The dimers assemble into filaments in a completely different way. b. They are different at the head and tail domains that are exposed at the surface. c. They do not differ. All intermediate filament proteins are identical. d. Their central rod domains are very different and do not all form coiled-coils.
They are different at the head and tail domains that are exposed at the surface
(Q008) Nuclear pores restrict larger molecules from traversing the membrane due to their
interwoven meshwork of protein fibrils
(Q019) Which of the following pathways helps selectively concentrate substances to be ingested by their binding to proteins on the cell surface?
receptor-mediated endocytosis
(Q001) Which of the following organelles is the site of steroid hormone synthesis in endocrine cells?
smooth ER
(Q014) In which process do Rab proteins function?
vesicle tethering
