Practice Exam Questions

Front 1

the mammalian cell cycle, exit from mitosis depends upon the degradation of:
a. cohesin.
d. securin.
b. condensin.
e. separase.
c. cyclin B.

Back 1

Cyclin B

Front 2

Ras is a:
a. growth factor
d. transcription factor
b. kinase
e. a GTPase switch protein
c. phosphatase

Back 2

a GTPase switch protein

Front 3

What happens to proteins that are modified by the covalent addition of multiple ubiquitin molecules?
a. they are targeted to the lysosome
b. they are targeted to the mitochondria
c. they are targeted for exocytosis
d. they are targeted for proteasomes
e. they are targeted for chaperons

Back 3

They are targeted for proteasomes

Front 4

What is the function of CapZ and tropomodulin in the sarcomere?
a. to center myosin thick filaments
b. to attach actin thin filaments to the Z disk
c. to stabilize the myosin thick filaments
d. to make contraction sensitive to Ca2+
e. to maintain a constant actin thin filament length

Back 4

to maintain a constant actin thin filament length

Front 5

In cells, the (g)-tubulin ring complex is found

Back 5

at the microtubule (-) end

Front 6

Which of the following properties is characteristic of malignant tumors?
a. localized to tissue of origin
b. invasive
c. well differentiated
d. low proliferation rates
e. all of the these

Back 6

invasive

Front 7

. Growing microtubule ends are normally “stabilized” by
a. a GDP cap
b. a GTP cap
c. phosphorylation of tubulin subunits
d. (g)-tubulin
e. dephosphorylation of tubulin subunits

Back 7

a GTP cap

Front 8

Which region of myosin interacts with actin filaments?
a. the head domain
b. the rod domain
c. the light chains
d. the tail domain
e. the neck domain

Back 8

the head domain

Front 9

All of the following statements about actin assembly are correct except:
a. ATP-actin can assemble into filaments
b. actin subunits can treadmill through an actin filament
c. actin assembly can produce force for movement
d. actin (-) ends assemble more rapidly than actin (+) ends
e. actin assembly can be delayed by thymocin β4

Back 9

actin (-) ends assemble more rapidly than actin (+) ends

Front 10

Which of the following is a target of the APC?
a. Scc1
b. Mitotic cyclin
c. S-phase cyclin
d. Separase
e. a and c

Back 10

Mitotic cyclin

Front 11

NF-κβ signaling is important in
a. development.
b. immunity.
c. inflammation.
d. cell division
e. all of these

Back 11

inflammation.

Front 12

All of the following statements about actin assembly are correct except
a. ATP-actin can assemble into filaments.
b. Actin subunits can treadmill through an actin filament.
c. Actin assembly can produce force for movement.
d. Actin (−) ends assemble more rapidly than actin (+) ends.
e. G-actin only occurs as monomers

Back 12

Actin (−) ends assemble more rapidly than actin (+) ends

Front 13

A stem cell is capable of
a. symmetric cell division
b. asymmetric cell division
c. pluripotency
d. self-renewal
e. all of these

Back 13

All of the above

Front 14

Separase initiates sister chromatid segregation at anaphase by cleaving:
a. APC
b. Cdc20
c. cyclin B
d. Scc1
e. securin

Back 14

Scc1

Front 15

A microtubule protofilament is formed by the
a. lateral association of only -tubulin subunits
b. head-to-tail association of only (g)-tubulin subunits
c. lateral association of tubulin dimers
d. head-to-tail association of tubulin dimers
e. head to tail association of actin monomers

Back 15

head-to-tail association of tubulin dimers

Front 16

Which of the following is not a common intracellular second messenger
a. inositol 1,4,5-trisphosphate (IP3)
b. 1,2 diacylglycerol (DAG)
c. adenosine triphosphate (ATP)
d. 3´-5´ cyclic guanine monophosphate (cGMP)
e. Ca2+

Back 16

adenosine triphosphate (ATP)

Front 17

Which of the following occurs during anaphase?
a. The spindle elongates.
b. Kinetochores remain attached to shortening kinetochore microtubules.
c. Chromosomes move to the spindle equator.
d. The spindle poles move closer together.
e. The MTOCs depolymerize the (-) end of the kinetochore microtubules

Back 17

Kinetochores remain attached to shortening kinetochore microtubules

Front 18

Many actin cross-linking proteins contain
a. an ATP-binding cleft
b. a head domain
c. a CH-domain
d. only one actin-binding site
e. a profilin-binding site

Back 18

a CH-domain

Front 19

Capture of microtubule (+) ends by chromosomes occurs during
a. metaphase.
b. prometaphase.
c. anaphase.
d. telophase
e. S-phase

Back 19

prometaphase

Front 20

All the following statement(s) about destruction of cyclins is (are) true except
a. Destruction is carried out by proteasomes.
b. Destruction is preceded by polyubiquitination.
c. Ubiquitination occurs at specific sites on target molecules.
d. Ubiquitin targets Cdks.
e. Destruction by polyubiquitination is nonreversible.

Back 20

Ubiquitin targets Cdks.

Front 21

Which of the following proteins promotes actin assembly and is involved in signal pathways controlling actin assembly at the plasma membrane?
a. myosin
b. profilin
c. thymosin (B)4
d. filamin
e. Rio-kinase

Back 21

profilin

Front 22

During which stage of the cell cycle is the chromosome content of a mammalian liver cell 1n?
a. G1
b. S
c. G2
d. M
e. none of these

Back 22

none of these

Front 23

In vertebrates the releases of caspases
a. stimulates cell proliferation
b. inhibits the growth of neurons
c. promotes differentiation
d. triggers apoptotic pathways
e. triggers DNA repair pathways

Back 23

triggers apoptotic pathways

Front 24

In paracrine signaling, the signaling molecule
a. acts on cells in close proximity to the secreting cell.
b. acts on target cells far away from the secreting cell.
c. acts on the same cells that secreted the signaling molecule.
d. is carried to the target cells by the blood.
e. is generally hormone based

Back 24

acts on cells in close proximity to the secreting cell

Front 25

The first line of defense against point mutations is:
a. BRCA1
b. cytochrome P-450
c. DNA polymerase
d. topoisomerase
e. Rad53

Back 25

BRCA1

Front 26

In the mitotic spindle, astral microtubules function to
a. connect the spindle poles
b. attach chromosomes to the spindle
c. carry out cytokinesis
d. allow the spindle to interact with the plasma membrane
e. align the kinetochore microtubules

Back 26

allow the spindle to interact with the plasma membrane

Front 27

Exit from mitosis depends upon the degradation of
a. cohesion.
b. condensin.
c. cyclin B.
d. securin
e. separase

Back 27

Cyclin B

Front 28

Which of the following classes of genes are implicated in the onset of cancer?
a. proto-oncogene
b. caretaker genes
c. tumor-suppressor genes
d. apoptotic genes
e. all of these

Back 28

proto-oncogene
caretaker genes
tumor-suppressor genes
apoptotic genes

Front 29

Which of the following is not a cell surface receptor?
a. Nuclear receptors
b. cytokine receptors
c. G-protein-coupled receptors
d. TGFβ receptors
e. receptor tyrosine kinases

Back 29

Nuclear receptors

Front 30

The class of coat proteins associated with retrograde transport from later to earlier Golgi cisternae and Golgi-to-ER transport is:
a) COPI
b) COPII
c) clathrin and adapter proteins
d) SCAP
e) uncharacterized

Back 30

COPI

Front 31

Sar1 and ARF proteins are involved in
a) cargo protein recruitment
b) vesicle fusion
c) coat assembly
d) vesicle targeting
e) vesicle pinching off

Back 31

coat assembly

Front 32

What happens to proteins that are modified by the covalent addition of multiple ubiquitin
molecules?
a) they are targeted to the lysosome
b) they are targeted to the mitochondria
c) they are targeted for exocytosis
d) they are targeted for proteasomes
e) they are targeted for chaperons

Back 32

they are targeted for proteasomes

Front 33

Mitogens are added to the medium of cultured human cells that are synchronized in mitosis. The mitogen is washed way after these cells have passed the restriction point in the cell cycle. These
cells will progress through the cell cycle then arrest in which phase?
a) S-phase
b) G2
c) mitosis
d) Go/G1
e) the cells will not arrest

Back 33

Go/G1

Front 34

Ras is a:
a) growth factor
b) kinase
c) phosphatase
d) transcription factor
e) a GTPase switch protein

Back 34

A GTPase Switch protein

Front 35

Which of the followin properties is not shared by all stem cells?
a) self renewal
b) symmetrical cell division
c) asymmetrical cell division
d) totipotency
e) undifferentiation

Back 35

totipotency

Front 36

Which ofthe following are characteristics common to all three cytoskeletal systems
(microfilaments, intermediate filaments, and microtubules)?
a) they are reorganized during mitosis
b) they bind nucleotides
c) they have attached sites for motor proteins
d) they possess inherent polarity
e) their composition is very homogeneous biochemically

Back 36

They are reorganized during mitosis

Front 37

Which of the following mutations to the G protein could render a G protein coupled receptor signaling pathway constitutively active?
a) G(a) cannot bind G(by)
b) G(a) cannot bind GTP
c) G(a) cannot bind GDP
d) G(a) cannot hydrolyze GTP
e) G(a) cannot release GDP

Back 37

G(a) cannot hydrolyze GTP

Front 38

Which of the following features would target soluble proteins to late endosomes and lysosomes?
a) A KDEL signal
b) mannose 6-phosphate M6P signal
c) a GPI anchor
d) an N-Acetylglucosoamine label
e) a Lyy-Lys-X-X COPI signal

Back 38

mannose 6-phosphate M6P signal

Front 39

Put the following steps in vesicular transport in the correct order:
1. assembly of the SNARE complex;
2. disassembly of the SNARE complex;
3. assembly of vesicular coats;
4. association of Rab with Rab effector
5. disassembly of vesicular coats

Back 39

assembly of vesicular coats

disassembly of vesicular coats

association of Rab with Rab effector

assembly of the SNARE complex

disassembly of the SNARE complex

Front 40

ln most cells, where do all microtubules originate?

Back 40

MOTC

Front 41

What factors account for the observed age-related increase in cancer?

Back 41

With ageing, there is a longer exposure to carceinogenes, thereby increasing the likely hood of cancer. Most cancers require both genetic predisposition, and an outside effect. Also, as systems age they begin to degrade, as in the decrease in telomere length

Front 42

What is a 2nd messenger

Back 42

A second messanger is a additional signal in the pathway that will also or continue the signal transduction. Ca2+ is a common second messanger

Front 43

Explain the differences between endocrine, paracrine, and autocrine signaling

Back 43

In endocrine signaling, signaling molecules are synthesized by one organ and act on distant target cells. In animals the signaling molecule is carried to target cells by the blood or other extracellular fluids. In paracrine signaling, the signaling molecules are released and affect only target cells in close proximity. In autocrine signaling, the cell that releases the signaling molecule is also affected by the released signaling molecule.

Front 44

Why are LOF (loss of function) mutations normally recessive?

Back 44

In loss of function mutations there is still a functioning copy of the gene

Front 45

What are some of the major similarities and differences between TGF(B) receptors, Receptor Tyrosine Kinase and Cytokine receptors?

Back 45

Similarites:
They each dimerize as a signal ligand binds to them. they each act as kinase upon activation and each function with a GTP switch protein.

Differences:
Tyrosine Kinase phosphorylate tyrosine residues, while cytokine receptors phosphorylate serine and the threonine