mcb exam 4 - problem set 7

Cdc25 (a Cdk phosphatase) is normally regulated by nutritional and other environmental factors to allow activation of cyclin/cdk at the appropriate time. If you made a mutation in yeast Cdc25 that removed this regulation and made the enzyme always active at the restrictive temperature, what would be the result? a) The cells would be unusually small b) The cells would be unusually large c) The cells would die d) The cells would be stuck in G2 e) The cells would function normally

a) The cells would be unusually small

If you made a mutation that knocked out Cdc25 (Cdk phosphatase) function, what would happen to the fission yeast cells? a) The cells would grow abnormally large b) The cells would be stuck in S phase c) The cells would be stuck in M phase d) The cells would be abnormally small e) The cells would be normal

a) The cells would grow abnormally large

What do CDKs do just before the end of G2 to initiate the events leading to mitosis? a) They phosphorylate substrates needed for the cell to enter mitosis. b) They de-phosphorylate substrates needed for the cell to enter mitosis. c) They polyubiquitinate proteins to allow the cell cycle to continue. d) They add acetyl groups to histones activating the genes with which they are associated. e) They degrade proteins that are inhibiting progress toward mitosis.

a) They phosphorylate substrates needed for the cell to enter mitosis.

The main function of gap junctions is to _______ between cells. a) allow small molecule communication b) prevent leakage c) facilitate adhesion d) affect separation e) allow fusion

a) allow small molecule communication

The activation of a membrane integrin by binding to molecules in the cytoplasm and the resultant increase in its affinity for an extracellular ligand is called ________. a) inside-out signaling b) outside-in signaling c) right-side-out signaling d) upside-down signaling e) integration

a) inside-out signaling

The specialized cell attachments in which epithelial cells form a seal between their membranes allowing them to act as a barrier are: a) tight junctions b) hemidesmosomes c) gap junctions d) adherens junctions e) a, b and d

a) tight junctions

The stage(s) in which cells are not in the cell cycle is a. G0 b. G1 c. S d. G2 e. both b & d

a. G0

You observe a cell line growing on a culture dish. The cells cover the entire surface of the dish and cell division ceases. You scrape and remove a circle of cells from the center of the dish. Cells bordering the circle start dividing and running through what appears to be a normal cell cycle. What phase of the cycle were they in before the circle of cells was removed from the middle of the plate? a. G0 b. G1 c. S d. G2 e. death

a. G0 - Cultured cells will divide until they cover the dish (confluence) and then signal each other to stop dividing (contact inhibition) and exit the cell cycle until conditions change.

Once a fission yeast cell passes START, the cell is committed to replication. What is responsible for activating the Cdk to pass START? a. G1 cyclin b. G2 cyclin c. S cyclin d. M cyclin e. G0 cyclin

a. G1 cyclin

___ is a lipid kinase that interacts with growth factor receptors and triggers signaling cascades that influence cell growth, while ___ is a protein kinase that phosphorylates targets that act to increase protein synthesis: a. PI 3-kinase , mTOR b. mTOR, PI 3-kinase c. receptor tyrosine kinase, mTOR d. receptor tyrosine kinase, PI 3-kinase e. PI(3,4,5)P3, mTOR

a. PI 3-kinase , mTOR

A scientist identifies a new cell type in the skin that migrates very fast when the cells are grown in culture dishes. She is an expert in wound-healing assays and wants to test a role for specific GTPases in this process. She uses RNA interference (RNAi) to deplete Rho, Rac, and Cdc42 in separate experiments, and finds that wounds close completely after 4h in control cells (when none of the proteins are depleted), but that the wounds close after 28h when Rho is depleted, after 24h when Cdc42 is depleted, and after 26h when Rac is depleted. How would you interpret these results? a. Rho, Rac, and Cdc42 are each important for cell migration in this cell line b. Rho, Rac, and Cdc42 are not important for cell migration in this cell line c. Rho, Rac, and Cdc42 are each important for cell migration in all cell lines d. Rho, Rac, and Cdc42 have the same functions in would healing in this cell line e. Rho, Rac, and Cdc42 have different functions in would healing in this cell line

a. Rho, Rac, and Cdc42 are each important for cell migration in this cell line

A graduate student notices that when he microinjects an antibody that specifically recognizes cyclinD into mammalian cells that DNA replication does not occur. Why does this happen? a. The antibody blocks the activity of cyclinD b. The antibody increases the activity of cyclinD c. The antibody binds to the DNA to prevent DNA polymerase from binding d. The antibody is contaminated with cyclinD e. The antibody increases the viscosity of the cell

a. The antibody blocks the activity of cyclinD

Which of the following events would be considered the 5th step in a model for cell motility: a. de-adhesion at the rear of the cell and tail retraction b. lamellipodial protrusion c. myosin-mediated cell body translocation d. adhesion of new focal contacts to the ECM beneath the lamellipodium e. activation of actin nucleation by the Arp2/3 complex

a. de-adhesion at the rear of the cell and tail retraction

When cyclin concentration is low, _____________. a. the kinase of MPF lacks the cyclin subunit and is thus inactive b. the kinase of MPF lacks the cyclin subunit and is thus active c. MPF activity is high and the cell enters M phase d. MPF activity is low and the cell proceeds through M phase e. a and d

a. the kinase of MPF lacks the cyclin subunit and is thus inactive

Ubiquitination marks proteins for: a overexpression b degradation by the proteasome c phosphorylation d a, b, & c e b & c

b degradation by the proteasome

If you made a temperature sensitive mutation in the fission yeast Wee1 kinase that made the enzyme hyperactive at the restrictive temperature, what would be the result? a) The cells will be unusually small b) The cells will be unusually large c) The cells will be stuck in M phase d) The cells would be stuck in G1 e) The cells would function fairly normal

b) The cells will be unusually large

What would be likely to happen to yeast cells in G1 if you were able to treat them with an inhibitor that specifically inactivated its only Cdk? a) Cdc25 phosphatase would be activated earlier than usual. b) The cells would remain in G1 and would not progress toward mitosis. c) Wee1 kinase activity would be turned off as well. d) The cells would be driven from G1 to mitosis. e) The cells would explode.

b) The cells would remain in G1 and would not progress toward mitosis.

In the above scenario, assume that CAK normally does not phosphorylate CDK until Wee1 has added its phosphate. If you made a temperature sensitive mutation in yeast that instead made the CAK able phosphorylate CDK at any time at the restrictive temperature, what would happen to the cells? a) They would be completely normal b) They would be smaller than normal c) They would be stuck in G2 d) They would grow abnormally large e) They would be stuck in Go

b) They would be smaller than normal

If you made a temperature sensitive mutation that made mammalian CDK1 inactive at 42°C, what would happen to the cells at 42°C? a) They would remain in G1 b) They would be stuck in G2 with replicated DNA c) They would not be able to replicate their DNA d) They would be stuck in S phase e) They would divide normally

b) They would be stuck in G2 with replicated DNA

If you made a mutation that inactivated the cyclin A gene at the non-permissive temperature (42°C) what would be the result? a) They would replicate DNA b) They would not replicate DNA c) They would remain in G0, quiescent state d) They would go directly to M phase e) They would accumulate at the G2/M transition

b) They would not replicate DNA

A scientist notices that when he inactivates an actin nucleator in mammalian cells, collagen folds into a triple helix that accumulates in the ER. How would you interpret these results? a. Actin assembly prevents the activity of an enzyme that hydroxylates collagen's prolines b. Actin assembly is important for collagen trafficking out of the ER c. After removing the nucleator, collagen adopted an unusual triple helix that prevented ER exit d. Actin assembly inhibits collagen trafficking from the Golgi to the ER e. Microtubules are important for collagen trafficking out of the ER

b. Actin assembly is important for collagen trafficking out of the ER

Cells lacking myosin II can move on less adhesive surfaces but not on very adhesive ones. Given these results, what does this suggest about cell movement? a. Contractile forces are required to squeeze the cell cytoplasm forward. b. Contractile forces are required to pull the rear off the sticky surface. c. Cells cannot form protrusions on very adhesive surfaces. d. Myosin II is required for protrusion. e. Contractile forces are not required for movement.

b. Contractile forces are required to pull the rear off the sticky surface.

The stage of the cell cycle in which proteins needed for cell division would likely be made is a. G0 b. G2 c. S d. M e. none of the above

b. G2

Which of the following statements is false a. Synapsis occurs during meiosis b. Rec8 functions as a cohesin during mitosis c. Homologous recombination between chromatids occurs during meiosis d. Centromeres separate during anaphase of mitosis e. A single cycle of chromosome replication occurs during mitosis and meiosis

b. Rec8 functions as a cohesin during mitosis

Which statement about proteoglycans is inaccurate: a. They have highly negatively charged polysaccharides attached. b. They are cytoplasmic glycoproteins c. They are part of the extracellular matrix. d. They consist of a protein core with side chains of repeating disaccharides. e. None; all of the above are true

b. They are cytoplasmic glycoproteins

The regulatory subunit of maturation-promoting factor ________. a. transfers a phosphate group to certain serines and threonines of specific protein substrates b. is called cyclin because its concentration rises and falls predictably as the cell cycle progresses c. converts ATP to ADP d. a and b e. a and c

b. is called cyclin because its concentration rises and falls predictably as the cell cycle progresses

Movement past the transition point near the end of G2 requires Cdk activation by _______. a. Na+ ions b. mitotic cyclins c. ADP d. Na+ -K+ ATPase e. mitotic chromatin

b. mitotic cyclins

Which of the following is a characteristic of glycosaminoglycans (GAGs)? a. a polysaccharide made of a single sugar neutral sugar b. repeating disaccharides that are very negatively charged c. repeating disaccharides that have neutral charges. d. a protein with repeating amino acid sequence e. a glycoprotein with long polysaccharides attached

b. repeating disaccharides that are very negatively charged

Which is the most accurate statement about what controls the phosphorylation events that regulate the cell cycle: a. the action of a kinase that is present only during mitosis. b. the action of a kinase that requires bound cyclin for its activity. c. the action of cyclins that are present only during mitosis. d. the action of a phosphatase that requires cyclin for its activity. e. the action of a phosphatase that is only present during one phase of the cell cycle.

b. the action of a kinase that requires bound cyclin for its activity.

What triggers the entry of a cell into mitosis? a. the addition of inhibitory phosphate groups to Cdk by Cdc25 phosphatase b. the removal of inhibitory phosphate groups from Cdk by Cdc25 phosphatase c. the addition of inhibitory phosphate groups to Cdk by Wee1 kinase d. the removal of inhibitory phosphate groups from Cdk by Wee1 kinase e. the removal of phosphate groups from Wee1 kinase

b. the removal of inhibitory phosphate groups from Cdk by Cdc25 phosphatase

What kind of interaction attaches polyubiquitin to the target protein a) Hydrophobic interactions b) Ionic interactions c) Covalent interactions d) Van der waals interactions e) Hydrophobic and ionic interactions

c) Covalent interactions

You are studying an animal where you inject fluorescein, a fluorescent dye, into a single cell on the surface epithelium of the animal. After a brief period of time, the dye spreads to cells neighboring the injected cell. What do you conclude? a) The cells are connected by a cell wall. b) The cells are connected by tight junctions. c) The cells are connected by gap junctions. d) The cells are connected by plasmodesmata. e) The cells are connected by zonulae adherens

c) The cells are connected by gap junctions.

If you made a temperature sensitive mutation that inactivated cyclin D at 42°C, what would happen to the cells at 42°C? a) They would continue to divide normally b) They would halt in the middle of mitosis c) They would accumulate at G1 d) They would accumulate at G2 e) They would become smaller over time

c) They would accumulate at G1

Which of the following statements is true a. Mitosis occurs in the sexual cycle while meiosis occurs in somatic cells b. In meiosis, cohesins are not involved in chromosome pairing c. In meiosis, the cellular progeny are haploid d. Tetrads form in both meiosis and mitosis e. Mitosis and meiosis each produce cellular progeny identical to the original parental cell

c. In meiosis, the cellular progeny are haploid

Suppose you engineered one group of cells to overexpress GFP-tagged E-Cadherin, and another group of cells to overexpress RFP-tagged N-cadherin, and then you mix the cells together in a culture dish. Over time what will you observe? a. A mixture of red and green cells resulting from heterophilic interactions between E- and Ncadherins. b. Segregated groups of red and green cells due to heterophilic interactions between E- and Ncadherins. c. Segregated groups of red and green cells due to homophilic interactions between E- and homophilic interactions between N-cadherins. d. A mixture of red and green cells resulting from homophilic interactions between E- and Ncadherins. e. None of the above; cadherins don't mediate cell-cell adhesion.

c. Segregated groups of red and green cells due to homophilic interactions between E- and homophilic interactions between N-cadherins.

If a yeast cell in G1 is moved from rich medium to a low nutrient medium, the cell will likely: a. Enter into S phase immediately b. Enter into M phase immediately c. Stay in G1 longer until it reaches the normal size to enter S phase d. Stay in G1 for the same amount of time as if it were left in rich medium and enter S phase when the bud is smaller than normal e. Enter into G2 phase immediately

c. Stay in G1 longer until it reaches the normal size to enter S phase

Once the signal that directs a cell to move from G1 to S phase has been generated, what does the cell do? a. The cell replicates its RNA. b. The cell grows larger. c. The cell replicates its DNA d. The cell degrades its RNA e. The cell condenses its chromatin

c. The cell replicates its DNA

A mutation in the gene encoding encoding proline hydroxylase results in malformed connective tissues. This results from a. a defect in laminin assembly b. a defect in fibronectin assembly c. a defect in collagen assembly d. a defect in focal adhesion formation e. a defect in integrin insertion into the plasma membrane

c. a defect in collagen assembly

Covalent associations between proteins are rare in cell biology. One exception is: a. polymerization of tubulin subunits into microtubules b. polymerization of actin subunits into actin filaments c. addition of ubiquitin to other cellular proteins d. a & b e. the formation of cyclin-CDK complexes

c. addition of ubiquitin to other cellular proteins

In fission yeast cells, at which sites is DNA replication initiated? a. at randomly selected sites b. at sites where histones are phospho-ubiquitinated c. at sites where pre-replication complexes had previously assembled d. at sites where RNA polymerase binds e. at sites in the cytoplasm

c. at sites where pre-replication complexes had previously assembled

A mutation in a cadherin gene could affect a. cell-cell adhesions called gap junctions b. cell-cell adhesions called tight junctions c. intermediate filament-associated cell-cell adhesions called desmosomes d. actin-associated cell-cell adhesions called adherens junctions e. mitosis and meiosis each produce cellular progeny identical to the original parental cell

c. intermediate filament-associated cell-cell adhesions called desmosomes d. actin-associated cell-cell adhesions called adherens junctions

In a migrating cell, what generates the contractile forces that pull the rest of the cell forward? a. a-actinin b. dynein c. myosin II d. kinesin e. haribo

c. myosin II

What enzyme attaches a chain of proteins to other proteins that have been targeted for degradation, thus ensuring their destruction in a proteasome? a. ubiquitinase b. protease c. ubiquitin ligase d. kinase ligase e. ubiquitin duplicitase

c. ubiquitin ligase

Which of the following signaling processes control cell growth: a protein phosphorylation by AKT b protein phosphorylation by mTOR c protein synthesis downstream of mTOR signaling d a,b, & c e b & c

d a,b, & c

When G1 phase cells and S phase cells are fused together, the G1 nucleus begins to replicate DNA. What conclusion would you draw from this result? a) G1 phase cytoplasm contains factors that prevent a cell from going into S phase. b) G1 phase cytoplasm contains diffusible factors that stimulate the initiation of DNA synthesis. c) S phase nuclei contain non-diffusible factors bound to the DNA that stimulate the initiation of DNA synthesis. d) S phase cytoplasm contains diffusible factors that stimulate the initiation of DNA synthesis. e) Fusion of any two cells will always causes S-phase

d) S phase cytoplasm contains diffusible factors that stimulate the initiation of DNA synthesis.

A tight attachment between a cell and its extracellular matrix is at a specialized adhesive structure is called a(n) ________. a) tight junction b) spot desmosome c) plasmodesmosome d) hemidesmosome e) a and d

d) hemidesmosome

The stage(s) of the cell cycle in which chromosomes are doubled for the whole stage a. G0 b. G1 c. S d. G2 e. interphase

d. G2

A graduate student has identified a temperature-sensitive mutant yeast strain whose growth arrests at 37C. She suspects that the mutation inactivates a CDK, but doesn't know which one it could be. How could she identify the specific gene that is mutated in this strain? a. She could introduce a plasmid into the yeast to expresses Wee1 b. She could microinject the yeast strain with Cdc25 protein c. She could mutagenize the strain again and look for revertants to normal growth d. She could introduce plasmids into the yeast to express CDK genes from a normal yeast e. She could introduce plasmids into the yeast to express CDK genes from the same mutant

d. She could introduce plasmids into the yeast to express CDK genes from a normal yeast

The following is/are true during degradation of the specified protein a. Ubiquitin protein ligases mediate addition of ubiquitin chains to cyclins b. Anaphase-promoting complex (APC/C) recognizes a conserved destruction box sequence in mitotic cyclins and promotes their polyubiquitination c. The entire MPF complex gets degraded d. a and b e. a and c

d. a and b

What conclusions have been drawn about the functioning of the maturation-promoting factor? a. Progression of cells into mitosis depends on an enzyme whose activity is to phosphorylate other proteins. b. MPF activity is controlled by a subunit whose concentration varies from one cell cycle stage to another. c. The activity of cyclins is controlled by maturation-promoting factor. d. a and b e. Cyclins degrade MPF by themselves.

d. a and b

What causes the rapid drop in Cdk activity that leads to the exit from mitosis and the entry into G1 typically exhibited by cells as they finish division? a. a rise in mitotic cyclin concentration b. a rise in G1 cyclin concentration c. a rise in G2 cyclin concentration d. a decrease in mitotic cyclin concentration e. a decrease in G1 cyclin concentration

d. a decrease in mitotic cyclin concentration

With respect to the cell cycle, which of the following would be an accurate description of the types of cells that one sees in vivo (in an organism)? a. highly specialized cells that lack the ability to divide b. cells that normally do not divide but can be induced to synthesize DNA and divide after an appropriate stimulus c. cells that normally possess a relatively high level of mitotic activity d. a, b and c

d. a, b and c

What external stimulation is required by mammalian cells to progress through S-phase after passing the Start checkpoint? a. presence of steroid hormones in their culture medium b. presence of Na+ ions in their culture medium c. presence of growth factors in their culture medium d. no external stimulation is required e. presence of vitamins in their culture medium

d. no external stimulation is required

Which of the following statements is false: a DNA damage checkpoints can stall progression through the cell cycle b Spindle checkpoints can stall progression through the cell cycle c Checkpoints are negative feedback mechanisms that block cell cycle progression d Checkpoints allow time for DNA repair and proper spindle positioning e None; all are true

e None; all are true

Which of the following signaling processes control cell growth: a protein phosphorylation by PI3K b lipid phosphorylation by PI3K c receptor binding by PI3K d a,b, & c e b & c

e b & c

A purpose of cell adhesions is to: a) Allow cells to adhere to other cells b) Allow cells to adhere to the ECM c) Allow communication between cells d) Allow cells to sense their environment e) All are true

e) All are true

Which of the following statements is false a) Some adhesions are the result of protein-protein interactions b) Some adhesions are the result of protein-carbohydrate interactions c) Some adhesion proteins are linked to intermediate filaments d) Some adhesion proteins are linked indirectly to actin filaments e) All are true

e) All are true

As concentrations of cyclin increase in a cell, _____________. a) CDK binds the cyclin subunit and is inactivated b) cyclin phosphorylates the CDK to activate it c) cyclin de-phosphorylates the CDK to activate it d) cyclin independently signals the cell to progress in the cell cycle e) CDK binds the cyclin subunit and is activated

e) CDK binds the cyclin subunit and is activated

Communication between cells of a multicellular organism involve all except a) Secreted protein ligands that bind to plasma membrane receptors b) Intermediate filaments linked to desmosome junctions c) Mechanical signals among cells attached to the same extracellular matrix d) Small molecules moving through pores between cells e) Microtubule motors transporting molecules between cells

e) Microtubule motors transporting molecules between cells

If you made a temperature sensitive mutation in Cdk2, what would happen to the cells when you shift to the restrictive temperature? a) They would accumulate at G2/M transition with replicated DNA b) They would accumulate at the G2/S transition with replicated DNA c) They would accumulate in G1 with replicated DNA d) They would accumulate in G2 with replicated DNA e) They would be stuck in G1 or S phase

e) They would be stuck in G1 or S phase

In addition to binding cyclin, what else contributes to CDK activation? a) Phosphorylation at an activating site on the Cdk b) Degradation of Cyclin Activating Kinase c) Removal of an inhibitory phosphate group from Cdk d) Phosphorylation of an activating site on cyclin e) a and c

e) a and c

What circumstances lead to a halt in the progress of the cell cycle? a) When chromosomal DNA is damaged. b) When chromosomal DNA is not damaged. c) When DNA replication is not completed. d) When the proteasome is activated. e) a and c.

e) a and c.

The catalytic subunit of maturation-promoting factor ____________. a) produces ATP b) transfers a phosphate group from ATP to certain amino acids of specific protein substrates c) transfers a phosphate group from ATP to all serine residues of specific protein substrates d) converts ATP to ADP e) b and d

e) b and d

You isolate a new species of budding yeast, sequence the genome, and find that it only has one cyclin gene, one CDK gene, a START checkpoint, and a mitotic checkpoint, that allow normal progression through the cell cycle. Your advisor suggests that you do a temperature sensitive screen for cell cycle mutants to show that cyclin and CDK work like they do in other organisms. In designing the experiment, you are thinking about the phenotype(s) that you would look for in the mutants. What would you expect to see in a population of cyclin mutant cells, which were at various points of the cell cycle at the beginning of the experiment, after exposing them to the restrictive (high) temperature? (Bonus: If there were 2 cyclin genes and you found mutants with no buds, what type of cyclin was mutated?) a. A mixture of cells with various bud sizes b. Cells with large buds c. Cells with small buds d. Cells with no buds e. A mixture of cells with no buds and cells with large buds

e. A mixture of cells with no buds and cells with large buds

How do actin filaments cause the front cell edge to protrude during cell movement? a. Severing actin filaments at the front cell edge causes a local weakening in the actin cortex that causes the cell membrane to protrude. b. Polymerization of actin filaments occurs throughout the cell causing it to expand outwards. c. Increased actin polymerization within the central cell body pushes bundles of actin filaments outwards at the front causing it to protrude. d. An increase in cytoskeletal contractility at the rear of the cell causes a protrusion to form at the front. e. Addition of G-actin to the plus ends of filaments at the leading edge forces the membrane to protrude.

e. Addition of G-actin to the plus ends of filaments at the leading edge forces the membrane to protrude.

Which of the following is not a role of integrins? a. Contact between intracellular structures to the extracellular matrices. b. Anchor cells to substrates in ECM. c. Transmit signals to the extracellular environment. d. Participate in specialized cell-to-cell adhesion structures. e. All are roles of integrins.

e. All are roles of integrins.

Which of the following is a likely function of the basal lamina? a. Generates signals that maintain cell survival. b. Serves as a substratum for cell migration and determines cell migration path. c. Separates adjacent tissues. d. Acts as a barrier to passage of cancer cells. e. All of the above are correct.

e. All of the above are correct.

How are traction forces produced by moving cells? a. From the binding of actin bundling proteins to the substratum. b. From the force generated by actin polymerization at the front cell edge. c. From the interaction between desmosomes and the extracellular matrix. d. From gravitational forces between the front and rear of the cell. e. From transmission of contractile forces produced by the cytoskeleton and adhesions to the substratum.

e. From transmission of contractile forces produced by the cytoskeleton and adhesions to the substratum.

The first transition point in yeast cells that commits the cells to entering S phase occurs just before the end of ___ and is called _______. a. G2, START b. G1, MPF c. G2, VAMANOS d. G1, BEGIN e. G1, START

e. G1, START

Fibronectin contains a. binding sites for other extracellular matrix components b. binding sites for cell surface receptors c. binding sites for cytoplasmic receptors d. binding sites for nuclei e. a and b

e. a and b

Research on yeast cells and many different mammalian cells has demonstrated that the progression through the cell cycle is regulated at distinct stages or points in the cell cycle where the cell becomes committed to starting a crucial event, like ___________. a. initiating DNA replication near the end of G1 b. entering mitosis near the end of G2 c. initiating DNA replication near the end of G2 d. entering mitosis near the end of G1 e. a and b

e. a and b

When a cyclin binds to a Cdk, what happens? a. a change in that catalytic subunit's conformation exposing its T-loop b. a change in that regulatory subunit's conformation exposing its T-loop c. activation of the catalytic subunit after phosphorylation by CAK d. activation of the regulatory subunit phosphorylation by CAK e. a and c

e. a and c

Cell cycle regulation requires a class of multi-subunit complexes called _____ that function as _______. a. SCF complexes, ubiquitin ligases b. ubiquitin complexes, RNA ligases c. anaphase-promoting complexes, DNA ligases d. anaphase-promoting complexes, ubiquitin ligases e. a and d

e. a and d

How do cells regulate the concentrations of cyclins and other key cell cycle proteins? a. They adjust the synthesis rates of these molecules at different points in the cell cycle. b. They adjust the destruction rates of these molecules at different points in the cell cycle. c. They direct these molecules into the ubiquitin-proteasome pathway at appropriate times. d. They direct these molecules into the glycolysis and Krebs cycle pathways. e. a, b and c

e. a, b and c

The proteasome a. removes misfolded or damaged proteins b. controls the amount of cyclin proteins c. degrades ubiquitinated proteins d. a & c e. a, b, & c

e. a, b, & c

Which of the following factors regulate cyclin-dependent kinases by operating in combination to brake or accelerate processes that influence a cell's progress through the cell cycle? a. cyclin concentration b. phospohorylation of the Cdk c. Cdk inhibitors d. controlled proteolysis e. all of the above

e. all of the above

Which of the following events does not occur during cell motility: a. focal adhesion assembly b. focal adhesion disassembly c. integrin-associated tyrosine kinase signaling pathways d. activation of Rho-family GTPases e. anterograde F-actin flow

e. anterograde F-actin flow

When cyclin concentrations are high, _____________. a. the kinase of MPF binds the cyclin subunit and is thus inactivated b. the kinase of MPF binds the cyclin subunit and is thus activated c. MPF activity is high and the cell enters M phase d. MPF activity is low and the cell stays in G2 phase e. b and c

e. b and c

What activates Cdks? a. association with steroid hormones b. phosphorylation at critical residues c. association with a regulatory subunit d. association with a cyclin e. b, c and d

e. b, c and d

The stage(s) of the cell cycle in which chromosomes are at least partially doubled a. G1 b. G2 c. S d. M e. b, c, & d

e. b, c, & d

The stage(s) of the cell cycle included in interphase is/are a. G0 b. G1 c. S d. G2 e. b, c, and d

e. b, c, and d

Which of the following molecules is/are likely to act as a ligand for an integrin? a. fibronectin b. laminin c. microtubules d. nuclear lamin e. both a and b could

e. both a and b could

MPF-like enzymes have been found in yeast and mammalian cells and have been shown to be involved in M phase regulation. They are the key agents orchestrating cell cycle activities. They are called _____. a. cyclin-dependent kinases b. cyclinases c. MPFases d. cdks e. cyclin-cdk complexes

e. cyclin-cdk complexes

A graduate student has identified a new extracellular matrix protein that binds to cells using a short arginine-glycine-aspartate peptide. This new protein is functionally related to the ECM protein ____ and likely binds to receptors called ____. a. collagen, catenins b. collagen, cadherins c. collagen, integrins d. fibronectin, cadherins e. fibronectin, integrins

e. fibronectin, integrins