Cell Bio Exam 3 (Another one)

Which of the following protein 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

a) ARP complexes

Which of the following kinases is responsible for phosphorylation and inactivation of M-Cdk? a) Wee1 kinase b) MAP kinase c) Akt kinase d) S-Cdk e) cdc25

a) Wee1 kinase

Which process provides the force that propels the leading edge of a motile cell forward? a) actin polymerization b) microtubule polymerization c) myosin I motor activity d) myosin II motor activity e) kinesin motor activity

a) actin polymerization

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) phosphorylating p53 d) by binding to Cdk inhibitors like p21 e) RB protein promotes escape from G0

a) by binding to and inhibiting E2F transcription factor

Which of the following proteins is required to sustain G1 phase? a) cdh1 b) p53 c) cdc25 d) mTOR e) myc

a) cdh1

At the metaphase-anaphase transition, which of the following proteins is ubiquinated by APC? a) cyclin B b) cdc20 c) separase d) cohesins e) none of the above are ubiquinated by APC

a) cyclin B

Which of the following protein complexes is capable of nucleating actin filaments? a) formin dimers b) gamma tubulin c) centrioles d) cofilin e) none are capable of nucleating actin filaments

a) formin dimers

Which of the following intermediate filaments is the cytoskeletal component of desmosomes between epithelial cells? a) keratins b) vimentin c) neurofilaments d) nuclear lamins e) none of the above

a) keratins

Growth factors increase protein synthesis and decrease protein degradation by activating which of the following? a) mTOR b) cdh1 c) cdc20 d) p53 e) myc

a) mTOR

Which of the following events prevents a second round of DNA replication? a) phosphorylation of ORC b) phosphorylation of cdc25 c) ubiquination of cyclin B d) ubquination of cdc6 e) none of the above

a) phosphorylation of ORC

Complete the following sentence. "Most kinesins 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

a) plus (+) end directed microtubule motor proteins

Complete the following sentence: Caspases are... a) proteases b) phosphatases c) ubiquitin ligases d) scaffold proteins e) kinases

a) proteases

Which of the following serves as the minus (-) end capping protein of actin filaments in striated muscle? a) tropomodulin b) troponin c) tropomyosin d) CapZ e) none of the above

a) tropomodulin

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 source is not known

b) ATP hydrolysis

Which of the following kinase-cyclin pairs is correctly matched? a) S Cdk & cyclin B b) G1-S Cdk & cyclin E c) M Cdk & cyclin C d) G1-Cdk & cyclin A e) All are correctly matched

b) G1-S Cdk & cyclin E

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

b) M-Cdk complex

Which small GTPase might be activated during remodeling of the actin cytoskeleton? a) Rab b) Rac c) Ran d) Ram e) dynamin

b) Rac

Which of the following is phosphorylated by S-Cdk to initiate DNA synthesis? a) DNA polymerase b) cdc6 c) MPF d) ORC e) Helicase

b) cdc6

Which of the following is NOT a microtubule organizing center (MOC)? a) centrosome b) centriole c) spindle pole d) basal body e) all of the above are MOCs

b) centriole

Complete the following sentence. "Cytoplasmic dyneins 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

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

Which of the following events occurs during prometaphase? a) DNA replication b) disintegration of the nuclear envelope c) ubiquination of cyclin B d) inactivation of APC e) formation of the contractile ring

b) disintegration of the nuclear envelope

During apoptosis, how does cytochrome C get out of the mitochondrion? a) it leaves through channels formed by "BH3 only" proteins b) it leaves through channels 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

b) it leaves through channels formed by "BH123" proteins

What is the function of the "GTP Cap" on microtubules a) it is a binding site for kinesin 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

b) it prevents catastrophic shortening of the microtubule

Which of the following statements is FALSE regarding microtubules? a) microtubules are composed to 13 "protofilaments" 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

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

During kinesin movement along a microtubule, what happens immediately after nucleotide exchange? a) the motor head releases the microtubule b) the neck linker "zippers" onto the leading head c) the trailing head dissocates d) the leading head binds tightly e) the leading head is thrust forward

b) the neck linker "zippers" onto the leading head

Which of following binds calcium ions and promotes skeletal muscle contraction? a) tropomodulin b) troponin complex c) tropomyosin d) calmodulin e) contractin

b) troponin complex

Mitogens promote entry into cell cycle by inactivating which of the following proteins? a) cdc20 b) p53 c) Rb d) cyclin D e) APC

c) Rb

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

c) binding of ATP

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

c) loss of cilia

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

c) neuronal axon

Which of the following best describes the microtubular structure of the axoneme of spermatozoa? a) nine sets of singlet microtubules surrounding two doublet microtubules b) nine sets of doublet microtubules surrounding one singlet microtubule c) nine sets of doublet microtubules surrounding two singlet microtubules d) nine sets of triplet microtubules surrounding one singlet microtubule e) nine sets of triplet microtubules surrounding two singlet microtubules

c) nine sets of double microtubules surrounding two singlet microtubules

Which of the following is phosphorylated by the M-Cdk complex? a) p53 b) securin c) nuclear lamin B d) p21 e) all of the above are substrates for M-Cdk

c) nuclear lamin B

What is smallest contractile unit in striated muscle cells? a) sarcophagus b) sarcoplasmic reticulum c) sarcomere d) sarcaster e) myosome

c) sarcomere

Which of the following refers to the SMC protein complex that gathers and organizes newly replicated DNA into chromosomes? a) gatherin b) compactin c) cohesin d) condensin e) compressin

d) condensin

What is the role of tropomyosin in striated muscle contraction? a) it is the minus (-) and capping protein in striated muscle b) it transmits 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 sies on actin filaments

d) it blocks myosin binding sites on actin filaments

How does cytochrome C initiate apoptosis? a) it promotes the aggregation of BH123 proteins in the outer membrane b) it aggregates to form channels in the outer mitochondrial membrane c) it directly activates executioner procaspases d) it promotes the recruitment of initiator procaspases e) none of the above

d) it promotes the recruitment of initiator procaspases

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 all animal cells

d) nuclear lamins

During G1 phase, which of the following prevents entry into S-phase when DNA damage is present? a) mTOR b) cdh1 c) cc20 d) p53 e) myc

d) p53

Which of the following compounds binds to actin filaments and s frequently used to as an affinity reagent for fluorescent labeling of the actin cytoskeleton? a) colchicine b) cytochalasin c) taxol d) phalloidin e) vincristine

d) phalloidin

What is the ultimate fate of apoptic cells? a) they aggregate in tissue to form scars b) they are processed to simple compounds by their own enzymes c) they remain 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

d) they are consumed by macrophages

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

e) Akt kinase

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? a) Mitotic Progress Facilitator b) Metaphase Promoting Factor c) Momma's Powerful Force d) Metaphysical Procreation Factor e) Maturation Promoting Factor

e) Maturation Promoting Factor

Complete the following sentence: the anti-apoptic protein, Bcl2, prevents apoptosis by... a) returning cytochome 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) a mechanism that is not listed above

e) a mechanism that is not listed above (preventing the aggregation of BH123 proteins)

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) cdc 20 e) cdc25

e) cdc25

Which of the following refers to the proteins that are cleaved by separase to release sister chromatids at anaphase? a) anaphase promoting complex (APC) b) cyclin B c) condensins d) separins e) cohesins

e) cohesins

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

e) dissociation of Pi

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

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

What is the role of the cyclin component of a cyclin-dependent protein kinase complex? a) it phosphorylates and activates the kinase b) it blocks the active site of the kinase c) it protects the kinase from ubiquination d) it is a phosphatase e) it determines the substrate specificity of the kinase

e) it determines the substrate specificity of the kinase

During cytokinesis, which of the following motor proteins closes the contractile ring? a) dynein b) kinesin c) dynamin d) myosin I e) myosin II

e) myosin II

Which of the following is TRUE regarding dynein motor proteins? a) they hydrolyze GTP and move toward the minus (-) end of the microtubule b) they hydrolyze GTP and move toward the plus (+) end of the microtubule c) they hydrolyze ATP and move toward the plus (+) end of the 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 the microtubule

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