Cell Bio Exam 3 (Rea Fall 2022)

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 stabilizes 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?

a. mitotic progress facilitator

b. metaphase promoting factor

c. momma's powerful force

d. metaphysical procreation factor

e. maturation promoting factor

Maturation promoting factor

At the metaphase-anaphase checkpoint, anaphase promoting complex (APC) ubiquinates which of the following proteins to release separate 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 kinesis dimer along a microtubules, 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?

a. it promotes the aggregation of BH123 proteins in the outer membrane

b. it aggregate to form channels in the outer mitochondrial membrane

c. it directly activates executioner procaspases

d. By promoting the aggregation/recruitment of initiator procaspases

e. none of the above

By promoting the aggregation of initiator procaspases

Which of the following statements is TRUE regarding most kinesis motor proteins?

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

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

keratin

What is the source of 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?

a. it phosphorylates and activates the kinase

b. it blocks the active site of the kinase

c. it protects the kinase from ubiquitation

d. it is phosphatase

e. it determines the substrate specificity of the kinase

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, Bc12

During the 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?

a. TOR

b. cdh1

c. cdc20

d. p53

e. myc

TOR

Which of the following statements regarding cytoplasmic dyenins is TRUE?

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

Which of the following kinesis 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?

a. tropomodulin

b. troponin

c. tropomyosin

d. CapZ

e. none of the above

Cap Z

Which of the following kinases is responsible of representing 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 initiated 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 damages 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 cdk 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?

a. centrosome

b. centriole

c. spindle pole

d. basal body

e. all of the above are MOCs

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 restyle in "power stroke"?

Dissociation of Pi

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

Vertebrate cilia

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

cohesion

Which of the following proteins 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 restrictive 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-cdk complex to prevent a second round of DNA synthesis?

ORC

Which of the following proteins 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 results 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 plasm membrane by which of the following membrane associated molecules?

Phosphatidyl inositol 3,4,5-triphosphate

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

a. gatherin

b. compactin

c. cohesin

d. condensin

e. compressin

condensin

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 kinesis motor proteins binds directly to chromatin?

Kinesin 4,10

How does the anti-apoptic protein, Bc12, prevents apoptosis?

By preventing the aggregation of BH123 protein

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?

a. sarcophagus

b. sacroplasmic reticulum

c. sarcomere

d. sarcaster

e. myosome

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?

a. Wee1

b. MAP kinase

c. Akt kinase

d. S-cdk

e. cdc25

Wee1

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

Rb Protein

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

a. S cdk and cyclin B

b. G1-cdk and cyclin C

c. G1-cdk and cyclin A

d. G1-S Idk and cyclin E

e. all are matched correctly

G1-Cdk and Cyclin C

Which of the following compounds bind to actin filaments and is frequently used to as an affinity reagent for fluorescent labeling of the actin cytoskeleton?

a. colchicine

b. cytochalasin

c. taxol

d. phalloidin

e. vincristine

phalloidin

Which of the following intermediate filaments is found in all animal cells?

a. keratins

b. vimentin

c. neurofilaments

d. nuclear lamins

e. all of the above are found in animal cells

nucelar lamins

Which of the following intermediate filaments is the cytoskeletal components of desmosomes between epithelial cells?

a. keratin

b. vimentin

c. neruofilaments

d. nucelar lamins

e. all if the above

keratins

Which of the following statements is FALSE regarding microtubules?

a. microtubules are composed of 12 protofilamets

b. microtubules grow fastest from the minus (-) end

c. microtubules display the property of dynamic instability

d. microtubules undergo "catastrophe", during which they fray at the plus (+) end

e. all of the above are TRUE regarding microtubules

microtubules grow fastest from the minus (-) end

Which of the following protein complexes is capable of nucleating actin filaments?

a. formin dimers

b. gamma tubular ring complexes

c. centrioles

d. cofilin

e. none are capable of nucleating actin filaments

formin dimers

Removal of the centrioles from a eukaryotic cell would result in which of the following?

a. disruption of actin cytoskeleton

b. disruption of microtubule cytoskeleton

c. loss of cilia

d. necrosis

e. apoptosis

loss of cilia

Which small GTPase might be activated during remodeling of the actin cytoskeleton?

a. Rab

b. Rac

c. Ran

d. Ram

e. dynamin

Rac

Which of the following is TRUE regarding dynein Motor proteins?

a. they hydrolyze GTP and move towards the minus (-) end of microtubule

b. they hydrolyze GTP and move toward the plus (+) end of microtubules

c. they hydrolyze ATP and move toward the plus (+) end of actin filament

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

e. they hydrolyze ATP and move toward the minus (-) end of microtubule

they hydrolyze ATP and move toward the minus (-) end of microtubule

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

a. actin polymerization

b. microtubule polymerization

c. myosin | motor activity

d. myosin || motor activity

e. kinesin motor activity

actin polymerization

After a myosin motor head has been "cocked" and is bound to the actin filament, which of the following events triggers the "power stroke"?

a. ATP hydrolysis

b. GTP hydrolysis

c. binding of ATP

d. binding of GTP

e. dissociation of Pi

dissociation of Pi

What is the function of the "GTP Cap" on microtubules

a. it is a binding site for kinesis motors

b. it prevents catastrophic shortening of the microtubule

c. it prevents the hydrolysis of GTP by the alpha subunit

d. it prevents the hydrolysis of GTP by the beta subunit

e. it is of no consequence

it prevents catastrophic shortening of the microtubules

During kinesis movement along a microtubule, what happens immediately after nucleotide exchange?

a. the motor head releases the microtubules

b. the neck liner "zippers" onto the leading head

c. the trailing head dissociates

d. the leading head binds tightly

e. the leading head is thrust forward

the neck linker "zippers" onto the leading head

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

a. hydrolysis of ATP

b. hydrolysis of GTP

c. binding of ATP

d. dissociation of ADP

e. dissociation of Pi

binding of ATP

Potential anticancer drugs might include agents that do which of the following?

a. prevent the polymerization of microtubules

b. prevent the depolymerization of microtubules

c. promote the depolymerization of microtubules

d. inhibit GTP hydrolysis at the plus (+) end of microtubules

e. drugs that have any of the above actions should be considered potential anticancer agents

drugs that have any of the above action should be considered potential anticancer agents

Complete the following sentence. "Most kinesis are..."

a. plus (+) end directed microtubule motor proteins

b. minus (-) end directed microtubule motor proteins

c. plus (+) end directed actin motor proteins

d. minus (-) end directed actin motor proteins

e. inactive structural proteins

plus (+) end directed microtubule motor proteins

Complete the following sentence. "Cytoplasmic dyenins are ..."

a. dimeric, plus (+) end directed microtubule motor proteins

b. dimeric, minus (-) end directed microtubule motor proteins

c. trimeric, plus(+) end directed microtubule motor proteins

d. trimeric, minus (-) end directed microtubule motor proteins

e. components of the nuclear envelope

dimeric, minus (-) end directed microtubule motor proteins

Which of the following best describes the micro tubular structure of the toneme of spermatozoa?

a. nine sets of single microtubules surrounding two doublet microtubules

b. nine sets of doublet microtubules surrounding one singlet microtubules

c. nine sets of doublet microtubules surrounding two singlet microtubules

d. nine sets of triplet microtubules surrounding one singlet microtubules

e. nine sets of triplet microtubules surrounding two singlet microtubules

nine set of doublet microtubules surrounding two singlet microtubules

Which of the following is NOT composed of actin filaments?

a. microvilli of epithelial cells

b. contractile ring

c. neuronal axon

d. lamellipodia

e. stress fibers

neuronal axon

Which of the following proteins complexes is responsible for the nucleation of actin polymerization at the leading edge of motile cells?

a. ARP complexes

b. Akt complexes

c. Bax complexes

d. APC complexes

e. none of the above

ARP complexes

What is the role of tropomyosin in striated muscle contraction?

a. it is the minus (-) end capping protein in striated muscle

b. it transmit action potentials to myofibrils

c. it opens calcium channels on the sarcoplasmic reticulum

d. it blocks myosin binding sites on actin filaments

e. it binds calcium and exposes myosin binding sites on actin filaments

it blocks myosin binding sites on actin filaments

Which of the following serves as the minus (-) end capping proteins of actin filaments in striated muscle?

a. tropomodulin

b. troponin

c. tropomyosin

d. CapZ

e. none of the above

tropomodulin

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

a. S cdk and cyclin B

b. G1-S cdk and cyclin E

c. M cdk and cylin C

d. G1-cdk and cyclin A

e. All are correctly matched

G1-S cdk and cyclin E

Which of the following events occurs during prometaphase?

a. DNA replication

b. disintegration of the nuclear envelope

c. ubiquitation of cyclin B

d. inactivation of APC

e. formation of the contractile ring

disintegration of the nuclear envelope

Which of the following binds calcium ions and promotes skeletal muscle contraction?

a. tropomodulin

b. troponin complex

c. tropomyosin

d. calmodulin

e. contractin

troponin complex

Which of the following proteins serves as the minus (-) end actin capping protein in the sarcomere?

a. tropomodulin

b. troponin complex

c. tropomyosin

d. calmodulin

tropomodulin

Which of the following proteins is the calcium sensor that triggers contraction in the sacromere?

a. tropomodulin

b. troponin complex

c. tropomyosin

d. troponin

troponin

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

a. mTOR

b. cdh1

c. cdc20

d. p53

e. myc

p53

Which of the following events prevents a second round of DNA replication?

a. phosphorylation of ORC

b. phosphorylation of cdc25

c. ubiquitation of cyclin B

d. ubiquination of cdc6

e. none of the above

phosphorylation of ORC

Which of the following phosphorylates and inactivates the Wee1 kinase at the onset of M-phase?

a. p53

b. M-cdk complex

c. S-cdk complex

d. APC

e. cdc25

M-cdk complex

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

a. DNA polymerase

b. cdc6

c. MPF

d. ORC

e. helicase

cdc6

Mitoges promotes entry into cell cycle by inactivating which of the following proteins?

a. cdc20

b. p53

c. Rb

d. cyclin D

e. APC

Rb

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

a. anaphase promoting complex (APC)

b. cyclin B

c. condensin

d. separins

e. cohesins

cohesins

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

a. phosphatase B

b. M phosphatase

c. cdc6

d. cdc20

e. cdc25

cdc25

Which of the following is phosphorylated by the M-cdk complex?

a. p53

b. securin

c. nucelar lamin B

d. p21

e. all of the above are substrates of M-cdk

nucelar lamin B

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

a. cyclin B

b. cdc 20

c. separase

d. cohesins

e. none of the above

cyclin B

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

a. the electrochemical gradient across the plasma membrane

b. ATP hydrolysis

c. GTP hydrolysis

d. catastrophic shortening of kinetochore microtubules

e. the energy is not known

ATP hydrolysis

During cytokinesis, which of the following motor proteins close the contractile ring?

a. dynein

b. kinesin

c. dynamin

d. myosin |

e. myosin ||

myosin ||

Which of the following proteins is required to sustain G1 phase?

a. cdc 1

b. p53

c. cdc25

d. mTOR

e. myc

cdh1

Some of the effects of growth factors are mediated through which of the following kinases?

a. protein kinase A

b. protein kinase C

c. CAK

d. Wee1 kinase

e. Akt kinase

Akt Kinase

How does RB protein prevent escape from G0?

a. by binding to and inhibiting E2F transcription factor

b. by binding to and inhibiting p53

c. by phosphorylating p53

d. by binding to cdc inhibitors like p21

e. RB protein promotes escape from G0

by binding to and inhibiting E2F transcription factor

Growth factor increase protein synthesis and decrease protein degradation by activating which of the following?

a. mTOR

b. cdh1

c. cdc20

d. p53

e. myc

mTOR

What is the ultimate fate of apoptotic cells?

a. they aggregate in tissue to form scars

b. they are processed to simple compounds by their own enzyme

c. they remind quiescent until activation of G1-S cdk

d. they are consumed by macrophages

e. they emerge in a parallel universe as components of anti-creatures

they are consumed by macrophages

Complete the following sentence: Caspases are....

a. proteases

b. phosphatases

c. ubiquitin ligases

d. scaffold proteins

e. kinases

proteases

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

a. returning cytochrome C to the mitochondrion

b. promoting the aggregation of "BH123" proteins

c. promoting the aggregation of "BH3 only" proteins

d. preventing the aggregation of "BH3 only" proteins

e. the mechanism is not listed

e. the mechanism is not listed

During apoptosis, how does cytochrome C get out of the mitcohindrion?

a. it leaves through channels formed by " BH3 only" protein

b. it leaves through channel formed by "BH123" proteins

c. it aggregates to form clusters that are membrane permeable

d. it binds to BH123 proteins and enters the cytosol

e. it binds to Bcl2

it leaves through channel formed by "BH123" proteins