Cell Bio Exam 3 Review

Agents that interfere with the dynamic instability of molecules, including taxol, colchicine, and vincristine, are effective anti-cancer chemotherapeutics. Why is taxol less toxic to normal cell?

Taxol actually stabilize microtubules

MPF refers to the substance present in the cytosol of Xenopus Oocytes that is capable of driving multiple cycles of M phase and S phase in vitro. What is MPF?

Maturation Promoting Factor

At the metaphase-anaphase checkpoint, anaphase promoting complex (APC) ubiquinates which of the following proteins to release separase from inhibition?

Securin

Where in a motile cell would you expect to find most ARP complex?

In the lamellipodium - Leading Edge

During the movement of kinesin dimer along a microtubule, which of the following events is responsible for the "power stroke"?

ATP exchange for bound ADP on the leading head

Which of the following proteins promotes the depolymerization of actin filaments near the lamellipodium of a motile cell?

Cofilin

How does cytochrome C promote apoptosis via the intrinsic pathway?

By promoting the aggregation of initiator procaspases

1. Which of the following statements is TRUE regarding most kinesin motor proteins?

They hydrolyze ATP and move towards the plus (+) end of the microtubules

Which of the following intermediate filament proteins that are exclusively expressed in epithelial cells?

Keratin

What is the source of the calcium that permits contraction of skeletal muscle?

Sarcoplasmic reticulum

What provides the force that drives chromosomal segregation during Anaphase A?

Catastrophic fraying of kinetochore microtubules

In addition to the activation of Cyclin-dependent protein kinases, what is the role of the cyclin subunit?

Determines the substrate specificity of the kinase

Which of the following proteins replaces cdc20 to maintain anaphase promoting complex (APC) activity during G1 phase?

Cdh1

How does the Akt kinase inhibit apoptosis?

By phosphorylating the BAD protein and releasing the anti-apoptotic protein, Bcl2

During movement of myosin motor proteins long actin filaments, which of the following events results in release of the motor head from the actin filament?

ATP binding

Growth factor signal through the AKT kinase, resulting in the phosphorylation and activation of which of the following?

TOR

Which of the following statements regarding cytoplasmic dyneins is TRUE?

They hydrolyze ATP and move towards the minus (-) end of microtubules

Which of the following kinesins promotes catastrophic depolymerization of microtubules?

Kinesin 13

Which of the following are intermediate filament proteins that are expressed in eukaryotic cells?

Nuclear lamins

Which of the following proteins serves as the plus (+) end capping protein of actin filaments in the sarcomere?

Cap Z

Which of the following kinases is responsible for preventing assembly of Ndc80 complexes on kinetochore microtubules?

Aurora-B Kinase

What are Caspases?

Proteases that cleave substrates at specific aspartate residue

How do activated T-cells initiate apoptosis via extrinsic pathway?

By activating the Fas Death Receptor on target cell

How does the Cytochrome C escape mitochondria promote apoptosis?

By leaving through channels in the outer membrane formed by BH123 proteins

When significant DNA damage is detected during G1 phase, P53 is release from inhibition and arrests cell cycle at the Start checkpoint to prevent replication of damaged DNA. How does P53 prevent entry into S phase?

By promoting the transcription of Cak inhibitors

Which of the following substrates is phosphorylated by the P13 kinase?

Phosphatidylinositol 4,5-biphosphate

Which of the following is NOT a microtubule organizing center?

Centriole

At the M-phase checkpoint, which of the following proteins is the phosphatase that removes the inhibitory phosphate group from M-Cdk complex?

Cdc25

During movement of myosin motor proteins along actin filaments, which of the following events results in "power stroke"?

Dissociation of Pi

Which of the following is NOT a substrate of M-Cdk complex?

Cohesion

Which of the following is NOT an actin-rich structure?

Vertebrate cilia

Which of the following protein determines the packing density of microtubules in axons?

Tau

At the leading edge of a motile cell, which of the following events provides the force that drives the lamellipodium forward?

Actin polymerization

You have isolated a temperature sensitive yeast mutant. When maintained at the resitritve temperature, all of the yeast cells are arrested at the Metaphase-Anaphase Checkpoint due to lost of function mutation of a single cell. Which of the following protein complexes is most likely to be responsible for this?

APC/C

During S-phase which of the following is phosphorylated by S-Ck complex to prevent a second round of DNA synthesis?

ORC

Which of the following protein complexes can nucleate actin polymerization in the absence of existing actin filament?

Formin Dimers

Failure of anaphase promoting complex (APC) to ubiquinates this protein would result in arrest of cell cycle at anaphase. Which of the following is this protein?

Cyclin B

Un-capped actin filaments "grow" - polymerize at the plus (+) end. What happens at the minus end?

Depolymerization

The AKT kinase is recruited to the plasma membrane by which of the following membrane associated molecules?

Phosphatidyl inositol 3,4,5-triphosphate

What is the term for the SMC protein complexes that gather and pack newly replicated DNA into chromosomes?

Condensins

Prolactin and some cytokines alter gene expression through which of the following signal transduction pathways?

JAK-STAT pathway

Disintegration of the nuclear lamina and the nuclear envelope occurs during which phase of mitosis?

Prometaphase

Which of the following kinesin motor proteins binds directly to chromatin?

Kinesin 4,10

How does the anti-apoptotic protein, Bcl2, prevents apoptosis?

By preventing the aggregation of BH123 proteins

Which of the following statements about microtubules is FALSE?

They are found only in soft bodied organism

What is the term for the smallest contractile unit of skeletal muscle?

Sarcomere

At which phase of the cell cycle do the SMC protein complexes that prevent premature separation of sister chromatids first assemble around DNA?

G1 phase

Which of the following proteins is responsible for phosphorylation and activation of M-Cdk?

Wee1

Which of the following is the inhibitory binding partner for transcription factor E2F?

Rb protein

Which of the following Cdk complex / cyclin matches is incorrect?

G1-Cdk and Cyclin C

In the lab, you have cultured cells that express a trimeric G protein of the Gi family. Which of the following best describes the expected result of pertussis toxin treatment on these cells?

cAMP levels go up

The effect of pertussis toxin treatment on trimeric G-protein signaling is due to which of the following covalent modifications?

ADP ribosylation of the alpha subunit

Which of the following G proteins signals through cMP phosphodiesterase in retinal rod & cone cells?

Gt

Which of the following best describes the events that occur after photoisomerization of 11-cis retinal in rod cells?

cGMP levels decrease, Nat channels close, the cell hyperpolarizes and glutamate release decreases

Which of the following small GTPases plays a key role in the mitogen activated protein (MAP) kinase pathway?

Ras

An extracellular messenger molecule that increases intracellular calcium levels in target cells, AND is blocked by pertussis toxin, probably signals through which of the following trimeric G-proteins?

Go

The PI3 kinase signaling pathway results in the activation of which of the following protein kinases?

Akt kinase

Janus kinases phosphorylate which of the following signal transduction proteins?

STATs

Phospholipase Cß activation leads to the production of (at least) two signaling molecules; inositol 1,4,5-trisphosphate (IP3) and diacylglycerol. What is the function of IP3?

it promotes the release of Ca2+ from the ER

Which of the following is an intermediate filament that is found in ALL eukaryotic cells?

Nuclear lamins

Which of the following statements is FALSE regarding microtubules?

microtubules grow fastest from the minus (-) end

What is the function of gamma tubulin ring complexes?

they nucleate polymerization of microtubules

Many anti-cancer drugs target the microtubule cytoskeleton. Which of the following best describes this class of anti-cancer drugs?

drugs that disrupt the dynamic instability of microtubules

What is the function of the centriole?

it is required for production of cilia

Which of the following is TRUE regarding most kinesin motor proteins?

they hydrolyze ATP and move toward the plus (+) end of the microtubule

Which small TPase is often activated during remodeling of the actin cytoskeleton?

Rac

During dynamic instability of microtubules, when does the "catastrophic" shortening of microtubules occur?

when the microtubule looses it's "GTP cap"

During kinesin movement along a microtubule, which event causes the neck linker to "zipper onto the head domain" (i.e., the "Power Stroke")?

exchange of ADP for ATP

What process provides the force that propels the leading edge of a motile cell forward?

actin polymerization

After release of the myosin head from an actin filament, which of the following events "cocks" the myosin head into the active conformation.

ATP hydrolysis

During myosin movement along an actin filament, which event causes release of the head domain from the actin filament.

binding of ATP

In a motile cell, where would you expect to find the highest concentration of the ARP complex?

in the lamellipodium

What is the smallest contractile unit in striated muscle cells?

sarcomere

Which of the following serves as the plus (+) end capping protein of actin filaments in sarcomeres?

CapZ

Which of the following proteins releases calcium from the sarcoplasmic reticulum in response to muscle depolarization?

a calcium-gated calcium channel

What is the role of tropomyosin in striated muscle contraction?

It blocks myosin binding sites on actin filaments

You have isolated a temperature sensitive yeast mutant. When maintained at the restrictive temperature, all of the yeast cells are arrested at the "start" checkpoint (G1-S transition) due to a loss-of-function mutation of a single gene. Below are listed five proteins. Which one is most likely to be the protein responsible for the observed phenotype (i.e., arrest at G1-S transition)?

Cyclin A

MPF refers to the substance(s) present in the cytosol of unfertilized Xenopus oocytes that is capable of driving multiple cycles of M phase and S phase in vitro. What is MPF?

Maturation Promoting Factor

Which of the following kinase-cyclin pairs is incorrectly matched?

G1 Cdk & cyclin C

Which of the following kinases is responsible for phosphorylation and inactivation of M-Cdk?

Wee1

Which of the following is phosphorylated by S-Cdk to initiate DNA synthesis?

Cdc6

Which of the following refers to the protein complex that gathers and organizes newly replicated DNA into chromosomes?

Condensin

Which of the following refers to the phosphatase that activates M-Cdk to initiate M-phase?

cdc25

What is the role of the cyclin component of Cdk complexes (e.g., M-Cdk)?

determines the substrate specificity of the kinase

Which of the following events occurs during prometaphase?

all of the above occur during prometaphase

Which of the following refers to the proteins that are cleaved by separase to release sister chromatids at anaphase?

Cohesins

At the metaphase-anaphase transition, which of the following proteins is ubiquinated by APC?

cyclin B

What is the energy source that drives chromosomal segregation during anaphase A?

kinetochore microtubule catastrophe

At the anaphase checkpoint, which of the following events must occur for mitosis to proceed?

ubiquination of cyclin B

What is the role of Hetl in the cell cycle?

it binds to APC to promote G1

How does P53 activation prevent entry into S-Phase?

by promoting the synthesis of Cdk inhibitors

How does RB protein prevent escape from G0?

by binding to and inhibiting E2F transcription factor

During G1 phase, which of the following prevents entry into S-phase when DNA damage is present!

P53

Complete the following sentence: Caspases are ...

proteases

Apoptosis can be induced by which of the following?

1. pro-caspase activation

2. expression of some Bcl-2 family genes

3. suppression of other Bcl-2 family genes

4. release of cytochrome C from mitochondria

How does cytochrome C initiate apoptosis?

it promotes the aggregation of initiator procaspases

Complete the following sentence: The anti-apoptotic protein, Bcl2, prevents apoptosis by...

preventing the aggregation of "BH123" proteins

Which of the following best describes the apical-to-basolateral order of occurrence of cell-cell junctions in an epithelial cell?

• tight junctions - desmosomes - adherens junctions - gap junctions

• tight junctions - adherens junctions - desmosomes - gap junctions

Which of the following cell-cell junctions is responsible for preventing the diffusion of solutes between apical and basolateral extracellular compartments in epithelial tissues?

Tight junctions

Which of the following cell-cell junctions is formed by cell adhesion molecules that are associated with actin filaments?

adherens junctions