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Cell Biology Exam 4 (OLD)
Terms in this set (49)
Which of the following statements about the cytoskeleton is FALSE?
Covalent bonds between protein monomers hold together cytoskeletal filaments
Which intermediate filament is inappropriately mismatched to its location?
Vimentins - Nucleus
Intermediate filaments help protect animal cells from mechanical stress because _____
filaments in each cell are indirectly connected to the filaments of a neighboring cell through the desmosome, creating a continuous mechanical link between cells
Which of the following statements is correct?
Kinesins and dynesins _______.
often move in opposite directions to each other
________ stabilize intermediate filaments (IFs) and link them to other IFs, microtubules, and microfilaments
Which of the following statements about actin is true?
Important for formation of the contractile ring during cytokinesis
This figure shows the leading edge of a limellipodium. Which of the following statements is false?
Capping proteins bind to the minus end of actin filaments
The following proteins are important for cell movement. Which of the following protein and its function is mismatched?
ARP - Regulation of the availability of actin monomers
Which of the following structures shorten during muscle contraction?
In the case of actin cytoskeleton, activation of different members of the Rho family affects the organization of actin filaments in different ways. For example, activation of ______ promotes lamellipodia
The following reactions are all common parts of a muscle contraction:
A. The muscle depolarizes and triggers an actions potential
B. Ca2+ ions cause the actin and myosin filaments to slide past each other.
C. Electrical excitation spreads into a series of membranous tubes called transverse tubules
D. The neurotransmitter released from the nerve terminal on to the muscle cell
E. The sarcoplasmic reticulum releases Ca2+ ions
D --> A --> C --> E --> B
Cell movement involves the coordination of many events in the cell. Which of the following phenomena is not required for cell motility?
Release of Ca2+ from the sarcoplasmic reticulum
In which phase of the cell cycle do cells check to determine whether the DNA is fully and correctly replicated?
At the end of G2
Progression through the cell cycle requires a cyclin to bind to a Cdk because ______
the binding of a cyclin to Cdk si required for Cdk enzymatic activity
Mitogens are _____
extracellular signals that stimulate cell division
How does S-Cdk help guarantee that replication occurs only once during each cell cycle?
It phosphorylates the Cdc6 protein, marking it for destruction
A safety device that operates in mammlian cels to restrain them from entering S phase with damaged DNA depends on a protein called _____, which accumulates in the cell in response to DNA damage and halts the cell-cycle control system in G1
The principle microtubule-organizing center in animal cells is the ____
Which of the following statements about the anaphase-promoting complex (APC) is false?
It is continuously active throughout the cell cycle
Which organelle fragments during mitosis?
A metastasis is _____.
A secondary tumor in a different part of the body that arises from a cell from the primary tumor
Which of the following descriptions of M-Cdk is FALSE?
It helps launch S phase
Which of the following statements about cancer cells is TRUE?
They show reduced dependence on signals from surrounding cells
The proliferate indefinitely
Multiple mutations are required to convert a normal cell into a cancerous cell
They are able to survive in foreign tissues but most normal cells die when misplaced
Which of the following genetic changes cannot convert a proto-oncogene into an oncogene?
A mutation that introduces a stop codon immediately after the codon for the initiator methionine
Adenomatous polyposis coli (APC) is a tumor suppressor and acts in the Wnt signaling parthway to prevent the TCF complex from turning on Wnt-responsive genes. Which of the following statements is FALSE?
When Wnt transmits its signal, APC prevents Beta-catenin from activating TCF in cells
A malignant tumor is more dangerous than a benign tumor because ______
Its cells invade other tissues
Which of the following does not occur during M phase in animal cells?
At the end of DNA replication, the sister chromatids are held together by the _____
Which of the following statements about microtubules is TRUE?
The dynamic instability of microtubules is critical for microtubule function
The poleward movement of chromosomes and concomitant shortng of kinetochore microtubules is known as A. _________; the separation of the poles themselves accompanied by elongation of the polar microtubules is known as B.________
A. Anaphase A
B. Anaphase B
Disassembly of the nuclear envelope ______
must occur for kinetochore microtubules to form in animal cells
Apoptosis differs from necrosis in that necrosis ________
causes cells to swell and burst, whereas apoptotic cells shrink and condense
Which of the following statements about apoptosis is TRUE?
Apoptosis is promoted by the release of cytochrome c into the cytosol from mitochondria
Which of the following statements is TRUE?
Cells can respond to the local mediators that they themselves produce. This is called autocrine signalling
Which of the following is likely to occur more rapidly in response to an extracellular signal?
Changes in protein phosphorylation
Which of the following statements about G-protein-coupled receptors (GPCRs) is FALSE?
GPCRs all have a similar structure with different numbers of transmembrane domains
For both actin and microtubule polymerization, nucleotide hydrolysis is important for _______
decreasing the binding strength between subunits on filaments
Which of the following statements about cyclic AMP is FALSE?
cAMP is formed by a cyclization reaction that removes one phosphate groups and joins two phosphate groups to the sugar parts of the AMP
Receptor tyrosine kinases (RTKs)
are activated by ligand-induced dimerization
Which of the following statements about the actions or targets of the second messengers of the phosphoinositide cascade is FALSE?
IP3 remains in the plasma membrane and DAG diffuses through the cytosol
Which of the following statements about the calmodulin-regulated kinase (CaM-Kinase II) is FALSE?
Becomes inactivated quickly after Ca+ levels have dropped
Intracellular signaling molecule activated by RTKs is
activates a G protein by locking it in the on state
Acetylcholine acts at a GPCR on heart muscle to make the heart beat more slowly. It does so by ultimately opening _______ channels in the plasma membrane, which decreases the cell's excitability by making it harder to depolarize the plasma membrane
The activation of ther serine/threonin protein kinase Akt requires phosphoinositide 3-kinase (PI 3-kinase) to ______.
create phosphorylated lipids that serve as docking sites that localize Akt to the plasma membrane
Akt promotes the survival of many cells by affecting the activity of Bad and Bc12, as diagrammed in this Figure....
In the absence of a survival signal, Bad is phosphorylated
Which of the following statements of this figure is TRUE?
gamma-tubulin rings are important for their nucleation
Gene mutations that disrupt intermediate filaments cause some rare human genetic diseases. Which of the following diseases is caused by mutation in a keratin?
Epidermolysis bullosa simplex
Phosphorylation by Akt indirectly activates ______, a kinase, which promotes cell growth. The anticancer drug rapamycin slows cell growth by inhibiting ______.
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