Cell Biology Exam 3 HW Questions Flashcards
(19 cards)
Kinesin is a motor molecule that is characterized by
a) activation of sliding in flagellar microtubules
b) sliding along actin in sarcomeres
c) motion toward the “positive” end of the microtubule
d) motion along actin filaments
e) motion toward the “minus” end of the microtubule
c) motion toward the “positive” end of the microtubule
The phase of the cell cycle associated with the doubling of the amount of DNA i the cell is
a) S phase
b) G1 phase
c) M phase
d) G2 phase
a) S phase
Cyclins modulate the progression of cells through the cell cycle by
a) directly activating G proteins
b) inducing synthesis of consitutively active forms of growth cell receptors
c) degradin ghistones
d) activating protein kinases that are critical regulators of cell division
e) increasing the production of DNA polymerases
d) activating protein kinases that are critical regulators of cell division
At the end of DNA replication, the sister chromatids are held together by the _____
a) kinetochores
b) cohesion proteins
c) securin proteins
d) histone proteins
e) condensin proteins
b) cohesion proteins
Which of the following statements about apoptosis is true?
a) Cells that consitiutively express Bcl2 will be more prone to undergo apoptosis
b) The prodomaion of procaspases contains the catalytic activity necessary for procaspase activation
c) Bax and Bak promote apoptosis by bining to procaspases in teh apoptosome.
d) Apoptosis is promoted by the releases of cytochrome c into the cytosol from the mitochondira.
D) apoptosis is promoted by release of cytochrome c into the cytosol from the mitochondira
Tight junctions _____
a) are formed from caudins and occludins
b) allow small water-soluble molecules to pass from cell to cell
c) interact with the intermediate filaments inside the cell
d) are found in cells in connective tissue
a) are formed from caudins and occludins
Which type of junction involves a connection to the actin cytoskeleton?
a) desmosomes
b) gap junctions
c) tight junctions
d) adherens junctions
d) adherens junctions
Which type of junctions are composed of connexin proteins?
a) Tight junctions
b) gap junctions
c) adherens junctions
d) all of the above.
b) gap junctions
Which of the following statements about the cytoskeleton is false?
a) They can stay intact in cells treated with concentrated salt solutions.
b) They can be found in the cytoplasm and the nucleus.
c) They can be anchored to the plasma membrane at a cell–cell junction.
d) Each filament is about 500 nm in diameter.
d) Each filament is about 500 nm in diameter.
Which of the following statements about the structure of microtubules is false?
a) Microtubules are built from protofilaments that come together to make a hollow structure.
b) α-Tubulin and β-tubulin are covalently bound to make the tubulin dimer that then assembles into protofilaments.
c) Within a microtubule, all protofilaments are arranged in the same orientation, giving the microtubule structural polarity.
d) The two ends of a protofilament are chemically distinct, with α-tubulin exposed at one end and β-tubulin exposed at the other end.
b) α-Tubulin and β-tubulin are covalently bound to make the tubulin dimer that then assembles into protofilaments.
The hydrolysis of GTP to GDP carried out by tubulin molecules ________________.
a) provides the energy needed for tubulin to polymerize.
b) occurs because the pool of free GDP has run out.
c) tips the balance in favor of microtubule assembly.
d) allows the behavior of microtubules called dynamic instability.
d) allows the behavior of microtubules called dynamic instability.
Which of the following statements about actin is true?
a) ATP hydrolysis decreases actin filament stability.
b) Actin at the cell cortex helps govern the shape of the plasma membrane.
c) Actin filaments are nucleated at the side of existing actin filaments in lamellipodia.
d) All of the above are true.
d) all
Which of the following events does not usually occur during interphase?
a) Cells grow in size.
b) The nuclear envelope breaks down.
c) DNA is replicated.
d) DNA is checked for mutations.
b)The nuclear envelope breaks down.
Levels of Cdk activity change during the cell cycle, in part because ________________.
a) the Cdks phosphorylate each other.
b) the Cdks activate the cyclins.
c) Cdk degradation precedes entry into the next phase of the cell cycle.
d) cyclin levels change during the cycle.
d) cyclin levels change during the cycle
The Retinoblastoma (Rb) protein blocks cells from entering the cell cycle by ______.
a) phosphorylating Cdk.
b) marking cyclins for destruction by proteolysis.
c) inhibiting E2F from acting as a transcription factor.
d) activating apoptosis.
c)inhibiting E2F from acting as a transcription factor.
Apoptosis differs from necrosis in that necrosis ________________.
a) requires the reception of an extracellular signal.
b) causes DNA to fragment.
c) causes cells to swell and burst, whereas apoptotic cells shrink and condense
d) involves a caspase cascade.
c) causes cells to swell and burst, whereas apoptotic cells shrink and condense
A malignant tumor is more dangerous than a benign tumor because
a) its cells are proliferating faster.
b) it causes neighboring cells to mutate.
c) its cells attack and phagocytose neighboring normal tissue cells.
d) its cells invade other tissues.
d) its cells invade other tissues.
Which of the following statements about tumor suppressor genes is false?
a) Gene amplification of a tumor suppressor gene is less dangerous than gene amplification of a proto-oncogene.
b) Cells with one functional copy of a tumor suppressor gene will usually proliferate faster than normal cells.
c) Inactivation of tumor suppressor genes leads to enhanced cell survival and proliferation.
d) Individuals with only one functional copy of a tumor suppressor gene are more prone to cancer than individuals with two functional copies of a tumor suppressor gene.
b) Cells with one functional copy of a tumor suppressor gene will usually proliferate faster than normal cells.
A pluripotent cell _________.
a) can only be produced in the laboratory.
b) can give rise to all the tissues and cell types in the body.
c) can only give rise to stem cells.
d) is considered to be terminally differentiated.
b) can give rise to all the tissues and cell types in the body.
