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Exam 9: Cell Communication

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Question 21

Multiple Choice

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You have identified a novel cytoplasmic protein.Through sequence analysis you are able to identify the presence of a number of serine/threonine phosphorylation motifs.Based on these data, you hypothesize that this protein may be a substrate for what kind of enzyme?

A) A protein kinase
B) A receptor tyrosine kinase
C) A G protein-coupled receptor
D) A tyrosine phosphatase

E) C) and D)
F) A) and B)

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Question 22

Multiple Choice

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Growth of new blood vessels is stimulated by vascular endothelial growth factor (VEGF) .This ligand binds to the VEGF receptor, which leads to the dimerization and autophosphorylation of this receptor on cytoplasmic tyrosines.What type of receptor is the VEGF receptor?

A) Channel-linked receptor
B) Enzymatic receptor
C) G protein-coupled receptor
D) Steroid hormone receptor

E) A) and B)
F) A) and C)

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Question 23

Multiple Choice

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If the effector protein phospholipase C failed to cleave phosphatidylinositol-4,5-bisphosphate (PIP₂) , the action of what enzyme would be affected?

What enzyme phosphorylates MAP kinase kinase?

Vasopressin is a hormone that is primarily released when the body is low on water.Release of vasopressin causes the kidneys to conserve water by concentrating urine and decreasing urine output.However, vasopressin also has additional functions in other tissues such as the brain and blood vessels, which are not directly involved in urine production.How could it be possible for vasopressin to trigger different responses in different tissues?

The function of adenylyl cyclase is to:

What signaling pathway commonly makes use of a G protein to transduce the signal?

Leptin is a circulating hormone that is produced by fat cells and plays a role in body metabolism and obesity.It normally binds to receptors in the brain and inhibits appetite.Studies have demonstrated that when obese mice that are leptin deficient are injected with leptin they quickly lose their excess weight.Interestingly, however, many overweight people have high levels of leptin in their bloodstream.Why do you think that the high levels of leptin in obese individuals are insufficient to curb their appetite?

In the nitric oxide signaling pathway, nitric oxide activates an enzyme that can convert many molecules of GTP into molecules of cGMP.cGMP is a small molecule that can diffuse through the cytoplasm and bind to an enzyme called protein kinase G (PKG) .Binding of cGMP to PKG leads to a change in the confirmation of PKG that leads to its activation.What type of signaling molecule is cGMP?

The cell surface receptors that can act only indirectly on plasma membrane-bound enzymes or ion channels are called:

Using a specific chemical, a cell biologist has blocked one type of channel-linked receptor in a lab rat's liver tissue.What was the likely mechanism of the chemical she used?

When bound to ligand, this type of receptor changes conformation to allow ions to move down their concentration gradient across the membrane:

What is similar about G protein-coupled receptors (GPCRs) and receptor tyrosine kinases (RTKs) ?

What type of receptor is not an enzyme, but is directly associated with an enzyme that can hydrolyze GTP?

What property defines most ligands for intracellular receptors?

You are interested in developing an inhibitor for the estrogen receptor.You have identified a molecule that is small and hydrophilic.In a test tube, this inhibitor binds tightly to the estrogen receptor, and inhibits the interaction of the receptor with estrogen.Do you think that this molecule will be an effective inhibitor of the estrogen receptor in cells?

Your research project involves the characterization of a particular signal transduction pathway.Specifically, you have been studying a receptor tyrosine kinase and protein X, which initiates downstream events.You are certain that protein X is part of the signal transduction pathway, but have been unable to identify a direct protein-protein interaction between the receptor tyrosine kinase and the protein X.What should you do next in your attempt to identify a link between the receptor tyrosine kinase and protein X?

A researcher is working to generate a new cancer drug.Thus far, he has identified a compound that can reduce the size of tumors in the lung.However, in order for the drug to work, the lung tumor has to be small.In addition, the tumor cannot have metastasized (spread to other areas of the body) .Furthermore, he knows that the drug acts to prohibit the signaling from one tumor cell to another tumor cell.Given the above information, this new drug prohibits:

In synaptic signaling, neurotransmitters are released into a space that is referred to as a:

One cell sends second messengers to another cell through gap junctions.What type of signaling would this be considered?