Cell Bio Exam 4
The nuclear lamina: A. Is made of intermediate filaments B. Supports and strengthens the nuclear envelope C. Is found under the nuclear envelope D. All of the above
D. All of the above
The process of homologous recombination: A. Has an intermediate called Holliday junctions B. Is initiated by double stranded DNA breaks C. Involves strand invasion D. All of the above
D. All of the above
Which of the following are functions of microtubules in cells? A. Movement of chromosomes during mitosis B. Positioning of the Golgi and ER C. Movement of vesicles D. All of the above
D. All of the above
p53 is known as the guardian of the genome. Which of the following are true of p53? A. It is a transcription factor B. p53 is stabilized in response to DNA damage C. p53 is phosphorylated after DNA damage D. All of the above
D. All of the above
p53: A. Is important for a cell cycle checkpoint in response to DNA damage B. Acts to activate transcription of a protein that inhibits the Cdk-cyclin complex C. Will prevent phosphorylation of Rb when active D. All of the above
D. All of the above
Myosin II: A. Is a single-headed motor B. Undergoes a power stroke when the head is bound to ATP C. "Walks" along an actin filament by repeated cycles of binding and releasing the actin filament D. All of the above
C. "Walks" along an actin filament by repeated cycles of binding and releasing the actin filament
A cell can rearrange its actin cytoskeleton in response to extracellular signals by: A. Activating small GTPases such as Cdc42 B. Decreasing the ATP concentration in the cytosol C. Increasing the activity of basal bodies D. All of the above
A. Activating small GTPases such as Cdc42
Desmosomes: A. Are a type of cell-cell interaction that provides mechanical strength B. Connect to actin filaments C. Link cells to collagen in the ECM D. All of the above
A. Are a type of cell-cell interaction that provides mechanical strength
Intermediate filaments: A. Are required for the mechanical strength of tissues B. Are always composed of the same protein C. Form thick filaments in the sarcomere D. All of the above
A. Are required for the mechanical strength of tissues
Which of the following statements about meiosis is true? A. During meiosis, the paternal chromosomes pair with the maternal chromosomes before lining up at the metaphase plate. B. Unicellular organisms that have a haploid state undergo meiosis instead of mitosis during cell division. C. Meiosis produces four genetically identical cells. D. In general, meiosis is faster than mitosis.
A. During meiosis, the paternal chromosomes pair with the maternal chromosomes before lining up at the metaphase plate.
Most cytoplasmic microtubules in interphase animal cells: A. Exhibit dynamic instability B. Have plus ends anchored at the centrosome C. Are organized with minus ends near the plasma membrane D. All of the above
A. Exhibit dynamic instability
Which type of cell-cell junction allows direct chemical and electrical communication? A. Gap Junction B. Tight Junction C. Adhesive Junction D. All of the above
A. Gap Junction
What effect does a MTOC like the centrosome have on the kinetics of microtubule assembly? A. It decreases the lag phase B. It decreases the elongation phase C. It eliminates the steady-state D. All of the above
A. It decreases the lag phase
What is the normal function of Rb? A. It regulates the activity of a transcription factor B. It binds to DNA C. It promotes DNA repair D. All of the above
A. It regulates the activity of a transcription factor
Mitogen signaling: A. Regulates the entry of a cell into S phase of the cell cycle B. Acts by inactivating Cyclin/Cdk complexes C. Activates Rb and promotes its binding to a transcriptional regulator (E2F) D. All of the above
A. Regulates the entry of a cell into S phase of the cell cycle
A type of cell-cell junction that allows epithelial cell sheets to serve as barriers to diffusion is called a: A. Tight junction B. Adherens junction C. Gap junction D. All of the above
A. Tight junction
Adherens junctions ______________________. A. can be used to bend epithelial sheets into tubes. B. are most often found at the basal surface of cells. C. are found only in adult tissues. D. involve fibronectin and integrin interactions.
A. can be used to bend epithelial sheets into tubes.
A cell can crawl through a tissue because of the transmembrane _________ proteins that can bind to fibronectin outside of the cell. A. integrin B. collagen C. gap junction D. claudin
A. integrin
A diploid cell containing 32 chromosomes will make a haploid cell containing ___ chromosomes. A. 8 B. 16 C. 30 D. 64
B. 16
Cell cycle checkpoints: A. Keeps the cell cycle moving when problems such as DNA damage are detected B. Act by inhibiting cyclin-Cdk complexes C. Function only during S phase D. All of the above
B. Act by inhibiting cyclin-Cdk complexes
What is a similarity between desmosomes and hemidesmosomes? A. Both contain integrins B. Both link to intermediate filaments such as keratin filaments C. Both are connections between a cell and the ECM D. All of the above
B. Both link to intermediate filaments such as keratin filaments
The sarcomere: A. Is the organization of the T tubules B. Contains thick and thin filaments C. Extends from one the I band to the H band D. All of the above
B. Contains thick and thin filaments
Fibronectin is an ECM protein that: A. Functions to make the tissue more elastic B. Links integrins to ECM molecules C. Is cleaved into an active form after secretion from the cell D. All of the above
B. Links integrins to ECM molecules
Fibronectin is an ECM protein that: A. Functions to make the tissue more elastic B. Links integrins to ECM molecules C. Is cleaved into an active form after secretion from the cell D. All of the above
B. Links integrins to ECM molecules
Which of the following statements about animal connective tissues is true? A. Enzymes embedded in the plasma membrane synthesize the collagen in the extracellular matrix extracellularly. B. Proteoglycans can resist compression in the extracellular matrix. C. Cells can attach to a collagen matrix by using fibronectin, an integral membrane protein. D. All of the above
B. Proteoglycans can resist compression in the extracellular matrix.
What is the effect of inhibiting the APC? A. Kinetochores cannot attach to microtubules B. Sister chromatids cannot separate C. Astral microtubules cannot form D. All of the above
B. Sister chromatids cannot separate
How do chromosomes move toward the poles in anaphase A? A. The motor dynein at the kinetochore walks toward the pole B. The action of a kinesin that acts at the poles and/or kinetochore to depolymerize microtubules C. The astral microtubules are pulled toward the cortex D. All of the above
B. The action of a kinesin that acts at the poles and/or kinetochore to depolymerize microtubules
Proteoglycans in the extracellular matrix of animal tissues ________________. A. chiefly provide tensile strength. B. allow cartilage to resist compression. C. are linked to microtubules through the plasma membrane. D. are polysaccharides composed of glucose subunits.
B. allow cartilage to resist compression.
Condensins: A. are degraded when cells enter M-phase B. assemble into complexes on the DNA when phosphorylated by M-Cdk C. bind to DNA before DNA replication begins D. All of the above
B. assemble into complexes on the DNA when phosphorylated by M-Cdk
During recombination __________________. A. sister chromatids undergo crossing-over with each other. B. chiasmata hold chromosomes together. C. one crossover event occurs for each pair of human chromosomes. D. the synaptonemal complex keeps the sister chromatids together until anaphase II.
B. chiasmata hold chromosomes together.
The influx of Ca++ into the cytosol of the muscle cell results in: A. Binding of Ca++ to actin filaments B. A physical block that prevents myosin from binding to the actin filament C. A conformational change that changes the position of tropomyosin on the thin filament D. All of the above
C. A conformational change that changes the position of tropomyosin on the thin filament
Which of the following are proteins that are phosphorylated by active M-Cdk? A. Microtubules B. Helicase C. Cdc25 D. All of the above
C. Cdc25
Which step in the myosin cycle is driven by ATP hydrolysis? A. Binding of the myosin head to the actin filament (cross-bridge formation) B. Power stroke C. Cocking of myosin head D. All of the above
C. Cocking of myosin head
During cell crawling, the function of myosin is to: A. Provide force for protrusion B. Attach to the ECM C. Contract the rear of the cell D. All of the above
C. Contract the rear of the cell
Which of the following are true of cyclins? A. The level of cyclin proteins is stable during the cell cycle B. Cyclins are the catalytic subunit of the cyclin-CDK complex C. Cyclins are targeted for degradation by the proteasome D. All of the above
C. Cyclins are targeted for degradation by the proteasome
The enzymatic activity of a cyclin-dependent kinase (CDK) is positively regulated by: A. Destruction of a cyclin protein B. Phosphorylation of CDK at inactivating sites C. Dephosphorylation of CDK at inactivating sites D. All of the above
C. Dephosphorylation of CDK at inactivating sites
Dynamic instability of MTs describes: A. Addition and loss of subunits with no net growth B. Coordinated polymerization of multiple microtubules C. Growth and shortening of individual microtubules in cells D. All of the above
C. Growth and shortening of individual microtubules in cells
A difference between cilia and flagella is that cilia: A. Are typically limited to one or two per cell B. Are longer C. Have an oar-like power stroke D. None of the above
C. Have an oar-like power stroke
Which of the following statements is true? A. Anaphase A must be completed before anaphase B can take place. B. In cells in which anaphase B predominates, the spindle will elongate much less than in cells in which anaphase A dominates. C. In anaphase B, microtubules associated with the cell cortex shorten. D. All of the above
C. In anaphase B, microtubules associated with the cell cortex shorten.
The Dam1 complex: A. Is found at centrosomes B. Acts as a clamp that slides along DNA during replication C. Keeps chromosomes attached to dynamic microtubules D. All of the above
C. Keeps chromosomes attached to dynamic microtubules
According to the GTP cap model, if a microtubule undergoes depolymerization, then growth, what has occurred? A. No change in the GTP cap B. Loss of the GTP cap C. Loss of the GTP cap, followed by regaining the GTP cap D. GTP cap is present, then lost
C. Loss of the GTP cap, followed by regaining the GTP cap
Which of the following are true about M phase cyclins? A. Cyclin levels fall slowly at the end of mitosis B. Levels of M-cyclin peak during interphase C. M-cyclin is tagged with ubiquitin for degradation by the proteasome D. All of the above
C. M-cyclin is tagged with ubiquitin for degradation by the proteasome
A difference between mitosis and meiosis is that: A. Meiosis does not require S phase first B. Mitosis produces 2 identical cells, while meiosis produces 2 different cells C. Meiosis has two divisions, one between homologs and one between sister chromatids D. All of the above
C. Meiosis has two divisions, one between homologs and one between sister chromatids
According to the "search and capture" model of chromosome attachment to the spindle: A. Kinetochores move until they find microtubules B. Microtubule dynamic instability is not important C. Microtubules probe until attached to kinetochores D. All of the above
C. Microtubules probe until attached to kinetochores
If an M phase and G1 cell are fused: A. The M phase nucleus enters G1 B. Both nuclei remain in their original cell cycle stage C. The G1 nucleus enters M D. Both nuclei enter Go
C. The G1 nucleus enters M
If the crosslinks between the outer doublets of a cilium are removed, then the: A. Cilium would bend normally B. The motor would not function C. The doublets would slide relative to each other D. All of the above
C. The doublets would slide relative to each other
Which of the following is true about Bcl family proteins? A. Some Bcl family members promote apoptosis, while others inhibit apoptosis. B. Bax and Bak are death-promoting members of the Bcl2 family that induce the release of cytochrome c from mitochondria into the cytosol. C. p53 can increase transcription of death-promoting Bcl2 family members D. All of the above
D. All of the above
Formation of a bipolar mitotic spindle always requires: A. Growth of microtubules from centrosomes B. The motor dynein to provide tension linking the poles to the cortex C. The motor kinesin to push the two poles apart D. All of the above
C. The motor kinesin to push the two poles apart
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.
Which of the following is true for BOTH meiosis and mitosis: A. formation of a bivalent B. genetically identical products C. condensation of chromosomes D. segregation of all paternal chromosomes to one cell
C. condensation of chromosomes
External signals can stimulate apoptosis by activating a set of cell-surface receptors known as: A. suicide receptors B. caspase receptors C. death receptors D. Bcl2 receptors
C. death receptors
Which type of junction contributes the most to the polarization of epithelial cells? A. adherens junctions B. desmosomes C. tight junctions D. gap junctions
C. tight junctions
The cell cortex is: A. The region just under the plasma membrane B. Enriched in actin filaments C. Important for cell shape D. All of the above
D. All of the above
The nuclear lamina: A. Is composed of intermediate filaments B. Is phosphorylated by M-cdk C. Disassembles at the onset of mitosis D. All of the above
D. All of the above
A cell cycle checkpoint: A. Allows the cell to arrest the cell cycle when something is wrong B. Monitors attachment of kinetochores to microtubules C. Acts at the G1 to S transition, or start, to make sure conditions are right for cell growth D. All of the above
D. All of the above
ARP complex (Arp2/3) functions in the formation of lamellipodia by: A. Binding to the side of existing actin filaments B. Nucleating growth of new actin filaments C. Reducing the lag phase of filament assembly by mimicking an actin dimer D. All of the above
D. All of the above
Actin filaments in the lamellipodium of a motile cell: A. Are organized in branched networks B. Are nucleated by the ARP complex C. Need capping proteins to keep filaments from becoming too long D. All of the above
D. All of the above
Both kinesin and dynein: A. Are two headed molecular motors B. Move along microtubules C. Bind to cargo through the tail domain D. All of the above
D. All of the above
Cadherins are molecules that: A. Are regulated by Ca++ B. Attach cells to one another at desmosomes C. Link to the actin cytoskeleton at adherens junctions D. All of the above
D. All of the above
Collagen: A. Is one of the most abundant proteins in vertebrates B. Has great mechanical strength C. Is a triple helix organized into fibrils, then fibers D. All of the above
D. All of the above
Cytokinesis in animal cells: A. Is the physical separation of cells after mitosis B. Occurs by a contractile ring C. Requires actin and myosin D. All of the above
D. All of the above
If a cell contains no cadherins: A. It will not stick to other cells B. It cannot form adherens junctions C. It can still adhere to the ECM D. All of the above
D. All of the above
Mad2: A. Inhibits the APC B. Is a kinetochore component C. Changes localization in response to microtubule attachment D. All of the above
D. All of the above
Mitogens provide a signal that allows cells to pass the G1 checkpoint. This type of signal transduction pathway results in: A. Activation of G1-Cdk B. Phosphorylation of Rb C. Transcription of genes needed for S phase D. All of the above
D. All of the above
Rho leads to formation of lamellipodia: A. When Rho is activated by a signaling pathway and binds GTP B. Since activated Rho stimulates a nucleating protein C. Because Arp2/3 becomes activated to nucleate actin filaments D. All of the above
D. All of the above
The T tubules: A. Are depolarized in response to a signal from the nerve terminal B. Are invaginations of the muscle cell plasma membrane C. Are located very close to the sarcoplasmic reticulum membrane D. All of the above
D. All of the above
During sexual reproduction, novel mixtures of alleles are generated. This is because ______. A. in all diploid species, two alleles exist for every gene. B. a diploid individual has two different alleles for every gene. C. every gamete produced by a diploid individual has several different alleles of a single gene. D. during meiosis, the segregation of homologs is random such that different gametes end up with different alleles of each gene.
D. during meiosis, the segregation of homologs is random such that different gametes end up with different alleles of each gene.
Fibroblasts organize the collagen of the extracellular matrix by ______________. A. cutting and rejoining the fibrils. B. processing procollagen into collagen. C. twisting fibrils together to make ropelike fibers. D. pulling the collagen into sheets or cables after it has been secreted.
D. pulling the collagen into sheets or cables after it has been secreted.
A single nondisjunction event during meiosis ____________. A. will block recombination. B. will occur only during meiosis II. C. cannot occur with sex chromosomes. D. will involve the production of two normal gametes and two abnormal gametes if it occurs during meiosis II
D. will involve the production of two normal gametes and two abnormal gametes if it occurs during meiosis II
T or F: According to the sliding filament model of muscle contraction, the thick filaments contract, or shorten, as myosin walks along the thin filaments
False
T or F: All cells in an adult organism are actively cycling.
False
T or F: All of the cells in an adult animal undergo meiosis.
False
T or F: An ECM with a large amount of proteoglycans and GAGs will be stiff, rigid, and lack water.
False
T or F: Cells in an epithelial sheet stick only to each other, not to the ECM.
False
T or F: Cilia and flagella have the same internal structure, but cilia are usually longer than flagella.
False
T or F: Connective tissue contains a high density of cells and little ECM.
False
T or F: Cytokinesis in plant cells is similar to cytokinesis in animal cells.
False
T or F: During S phase, the nuclear DNA is replicated, and chromosomes become highly condensed.
False
T or F: Intermediate filaments, actin filaments, and microtubules are all non-polar and relatively stable.
False
T or F: Interphase is the part of the cell cycle when nuclear and cytoplasmic division occur.
False
T or F: Kinetochore proteins bind to the tubulin molecules at the minus end of microtubules.
False
T or F: Microtubules are the smallest of the three cytoskeletal filaments.
False
T or F: Microvilli move due to myosin acting on actin filaments
False
T or F: Proteoglycans and GAGs are hydrophobic.
False
T or F: The cell cycle control system is very different between different eukaryotes such as yeast and humans.
False
T or F: The centromere nucleates a radial array of microtubules called an aster, and its duplication is triggered by S-Cdk.
False
T or F: The levels of CDK protein change during the cell cycle.
False
T or F: The motor protein required for movement of cilia and flagella is called ciliary kinesin.
False
T or F: When the myosin head is bound to ATP it is tightly bound to the actin in the thin filament.
False
T or F: p53 is degraded in response to DNA damage.
False
T or F: Kinesin motors generally move toward the plus ends of microtubules, while dynein is a minus end directed microtubule motor.
True
T or F: Actin polymerization provides force that drives membrane protrusion during formation of a lamellipodium.
True
T or F: Active M-Cdk leads to activation of more M-Cdk in a positive feedback loop.
True
T or F: Animal connective tissues consist largely of extracellular matrix.
True
T or F: Apoptosis is mediated by intracellular proteases, one of which is called the initiator since it activates other caspases.
True
T or F: Bone is an example of a tissue that is high in ECM
True
T or F: Both microtubule dynamics and microtubule motors play a role in chromosome movements during mitosis.
True
T or F: CDK/cyclin complexes are the "engine" of the cell cycle because they are required for cells to move through the stages of the cell cycle.
True
T or F: Cells regulate actin organization and dynamics through different types of actin binding proteins.
True
T or F: Defects in Rb lead to an eye tumor known as retinoblastoma.
True
T or F: Each cell cycle phase is regulated by a particular combination of cyclins bound to Cdks.
True
T or F: Integrins are heterodimers that have extracellular regions that bind to ECM components.
True
T or F: Integrins are involved in attachment of cells to the ECM and in signal transduction.
True
T or F: Integrins are transmembrane proteins that are linked to actin filaments.
True
T or F: Interphase consists of G1, S, and G2.
True
T or F: Kinesin is a processive motor that keeps one head bound while "walking" along the filament.
True
T or F: Movement of vesicles from ER to Golgi to plasma membrane occurs primarily along microtubules.
True
T or F: Proteins in the ECM are typically glycosylated.
True
T or F: S-Cdk initiates DNA replication by phosphorylating proteins at the replication origin.
True
T or F: The basal lamina is a special type of ECM to which epithelial cells attach.
True
T or F: The contraction of skeletal muscle in response to a signal from a neuron requires Ca++ channels in the T tubule and ER membranes.
True
T or F: The microtubule subunit is a heterodimer of α and β tubulin, both of which bind GTP.
True
T or F: The rate-limiting step of actin nucleation is trimer formation.
True
T or F: The sarcoplasmic reticulum is a specialized ER in muscle cells that stores and releases Ca++.
True
T or F: The three types of microtubules in the mitotic spindle are kinetochore, astral, and interpolar.
True