Question 1

Addison's disease is a disorder that results from a reduction in production of glucocorticoids and mineralocorticoids.Individuals with Addison's disease suffer from a variety of systemic symptoms including: muscle weakness, fever, issues with the gastrointestinal tract, and increased tanning.Considering this information, what type of signaling do you think that glucocorticoids and mineralocorticoids stimulate?

Accepted Answer

A)  Direct contact
B)  Paracrine
C)  Endocrine
D)  SynapticE) A) and D)
F) All of the above

Question 2

You are planning to perform some protein-protein interaction studies to identify a receptor for a steroid hormone you have been working on.You start by fractionating the cell.What cell fraction would you want to work with to identify the steroid hormone receptor of interest?

Accepted Answer

A)  The plasma membrane fraction
B)  The extracellular fraction
C)  The cytoplasmic fraction
D)  The mitochondrial fractionE) All of the above
F) A) and D)

Question 3

How are receptor tyrosine kinases and steroid hormone receptors similar?

Accepted Answer

A)  Both are activated by autophosphorylation
B)  Both are transmembrane proteins with a single transmembrane domain
C)  Both have a DNA-binding domain
D)  Both have a site for binding ligandE) A) and B)
F) A) and C)

Question 4

These molecules can directly convert extracellular signals into intracellular signals.

Accepted Answer

A)  Second messengers
B)  Scaffolds
C)  Membrane receptors
D)  Adapter proteinsE) None of the above
F) B) and C) C

Question 5

Many receptor tyrosine kinase (RTK)  pathways lead to the activation of Ras.To activate Ras, it is necessary to recruit a guanine nucleotide exchange factor to the plasma membrane, because Ras is a membrane associated protein.Guanine nucleotide exchange factors, such as SOS, stimulate the exchange of GDP for GTP.However, SOS cannot bind directly to most RTKs.The protein Grb2 has a domain that can bind to phosphorylated tyrosines, and another domain that can bind to SOS.Therefore, Grb2 can bind to active RTKs and recruit SOS to the plasma membrane.Grb2 is an example of what kind of signaling molecule?

Accepted Answer

A)  Scaffold
B)  Adapter protein
C)  Second messenger
D)  EnzymeE) C) and D)
F) B) and D) B

Question 6

You are performing an experiment to assay phosphorylation of a substrate by a protein kinase.Based on the data in the table below, what do these experimental results suggest?

Accepted Answer

A)  GTP is not required for phosphorylation.
B)  The substrate can undergo autophosphorylation.
C)  The substrate is not required for phosphorylation.
D)  The protein kinase is required for phosphorylation.E) A) and B)
F) B) and C)

Question 7

You are having lunch with an elderly friend when suddenly he begins to experience chest pain and tightness.He reaches into his pocket, gets out one of his nitroglycerin tablets and quickly takes it.After the episode passes, your friend asks you how the nitroglycerin helps his angina.You explain that nitroglycerin gets converted by cells to nitric oxide (NO)  causing the smooth muscle cells of the blood vessel to relax and increase blood flow to the heart.He pushes you for a more detailed explanation, so you explain further that:

Accepted Answer

A)  NO activates guanylyl cyclase, which catalyzes the synthesis of cGMP, which acts as an intracellular messenger in a pathway leading to smooth muscle relaxation.
B)  NO activates a protein kinase which catalyzes the synthesis of cGMP, which acts as an intracellular messenger in a pathway leading to smooth muscle relaxation.
C)  NO inhibits guanylyl cyclase, which allows the build up of cGMP, which acts as an intracellular messenger in a pathway leading to smooth muscle relaxation.
D)  NO activates cGMP, which catalyzes the synthesis of guanylyl cyclase, which acts as an intracellular messenger in a pathway leading to smooth muscle relaxation.E) All of the above
F) A) and C)

Question 8

Ste5 binds to MAPKKK, MAPKK, and MAPK to organize the kinase cascade.What type of signaling molecule is Ste5?

Accepted Answer

A)  Scaffold
B)  Adapter protein
C)  Second messenger
D)  EnzymeE) A) and C)
F) None of the above

Question 9

A mutation that affects Ca++ binding to calmodulin is most likely to interfere with what aspect of a signal transduction pathway?

Accepted Answer

A)  The flow of Ca++ ions through ion channel receptors
B)  The cellular response to the second messenger
C)  The MAP kinase cascade
D)  G protein activityE) None of the above
F) B) and C) B

Question 10

What is the difference between Ras and the G proteins bound to G protein coupled receptors (GPCRs) ?

Accepted Answer

A)  Ras is an enzyme and the G proteins bound to GPCRs are not enzymes.
B)  Ras is a second messenger and the G proteins bound to GPCRs are not second messengers.
C)  Ras is a small G protein and the G proteins bound to GPCRs are not small G proteins.
D)  Ras can activate different effector molecules and the G proteins bound to GPCRs cannot activate different effector molecules.E) A) and B)
F) A) and D)

Question 11

Tamoxifen is a drug that is used to treat breast cancer.It inhibits the activities of the estrogen receptor in breast epithelial cells, which are the cells that are relevant to breast cancer.One of the concerns that scientists had during the development of Tamoxifen as a therapy for breast cancer was that other cell types require estrogen signaling for their function.For example, it is known that cells in bone tissue require estrogen signaling.As a result, there was a concern that use of Tamoxifen would lead to bone loss in patients.In reality, however, researchers were surprised to find that Tamoxifen actually led to an increase in bone density in breast cancer patients.At the same time, Tamoxifen did inhibit the activity of the estrogen receptor in breast epithelial cells in these patients.What is the best explanation for this finding?

Accepted Answer

A)  Tamoxifen binds different parts of the estrogen receptor in different tissues.
B)  The estrogen receptor is bound to different coactivators in different tissues.
C)  Tamoxifen can only enter certain cell types.
D)  Bone cells make use of a different type of estrogen receptor that does not bind to Tamoxifen.E) B) and C)
F) A) and D)

Question 12

A mutation in the DNA-binding domain of a steroid hormone receptor is most likely to affect what aspect of receptor function?

Accepted Answer

A)  The conformational change of the receptor
B)  The binding of the hormone to the receptor
C)  The translocation of the receptor to the nucleus
D)  The cellular response to the hormoneE) All of the above
F) C) and D)

Question 13

G protein-coupled receptors are the largest family of cell surface receptors.Each receptor passes through the plasma membrane how many times?

Accepted Answer

A)  Once
B)  Three times
C)  Five times
D)  Seven timesE) A) and B)
F) B) and C)

Question 14

The protein SOS is a guanine nucleotide exchange factor for Ras.SOS helps facilitate the exchange of GDP for GTP.What would be the effect of a mutation that inhibits the interaction between SOS and Ras?

Accepted Answer

A)  GTP would remain bound to Ras, thereby keeping Ras constitutively active.
B)  GDP would remain bound to Ras, thereby preventing Ras activation.
C)  Ras would be more likely to hydrolyze GTP to GDP.
D)  There would be no effect.E) A) and B)
F) A) and C)

Question 15

You have identified a molecule, molecule X, that can bind to the ATP binding site of a specific protein kinase, and prevent ATP binding.You are conducting a kinase assay using this protein kinase and a known substrate of this kinase, and have set up the reaction using the proper conditions and co-factors to allow for optimal protein kinase activity.If you add molecule X to the reaction, what do you predict will be the outcome?

Accepted Answer

A)  The substrate will be phosphorylated normally in the presence of molecule X.
B)  Less phosphorylation of the substrate will be seen in the presence of molecule X.
C)  More phosphorylation of the substrate will be seen in the presence of molecule X.D) A) and C)
E) None of the above

Question 16

In response to injury, cell fragments called platelets get activated to induce clotting.Activated platelets release factors that can in turn bind to specific membrane receptors on nearby cells.What type of signaling would this be considered?

Accepted Answer

A)  Direct contact
B)  Paracrine
C)  Endocrine
D)  SynapticE) A) and D)
F) B) and D)

Question 17

Some cancers are caused by the overexpression of receptor tyrosine kinases (RTKs) .It is known that RTK signaling pathways commonly stimulate cell division.Why would the overexpression of receptor tyrosine kinases lead to cancer development?

Accepted Answer

A)  RTKs are activated by dimerization, caused by ligand binding.If there are too many receptors on the cell surface, it is possible that these receptors dimerize in the absence of ligand binding, thus stimulating cell division at inappropriate times.
B)  If there are too many RTKs on the cell surface, this will tend to allow cells to adhere to each other.Once they adhere, RTKs from one cell can bind to RTKs from another cell, and they can activate each other leading to activation of downstream signaling pathways in both cells.
C)  If there are too many RTKs on the cell surface, it is less likely that inhibitors will bind to all of the available RTKs and block their ability to enter the nucleus.As a result, some of the RTKs will be able to enter the nucleus to stimulate transcription.
D)  If there are too many RTKs on the cell surface, this will promote the inhibition of autophosphorylation.In the absence of autophosphorylation, it is more likely that the RTK downstream signaling pathway will be active.E) A) and B)
F) None of the above

Question 18

Some enzymatic receptors and most G protein-coupled receptors transmit the signal into the cytoplasm by utilizing other substances within the cytoplasm that are referred to as:

Accepted Answer

A)  genes.
B)  intracellular receptors.
C)  second messengers.
D)  first messengers.E) A) and D)
F) B) and D)

Question 19

Many receptor tyrosine kinase pathways have MAPK as a downstream signaling component.MAPK can phosphorylate target proteins.What type of signaling molecule is MAPK?

Accepted Answer

A)  Scaffold
B)  Adapter protein
C)  Second messenger
D)  EnzymeE) A) and D)
F) None of the above

Question 20

Why are phosphorylation and dephosphorylation reactions commonly used to regulate signal transduction pathways?

Accepted Answer

A)  Phosphate groups are efficient second messengers
B)  Protein kinases and phosphatases are abundant in most cells
C)  The hydrolysis of bound GTP generates GDP, which can change the activity of proteins bound to GDP
D)  The addition or removal of a phosphate group can expose or hide potential binding sites in proteins or change protein activityE) None of the above
F) A) and B)

Exam 9: Cell Communication

Correct Answer
verified

You are planning to perform some protein-protein interaction studies to identify a receptor for a steroid hormone you have been working on.You start by fractionating the cell.What cell fraction would you want to work with to identify the steroid hormone receptor of interest?

Correct Answer
verified

How are receptor tyrosine kinases and steroid hormone receptors similar?

Correct Answer
verified

These molecules can directly convert extracellular signals into intracellular signals.

Correct Answer
verified
C

Correct Answer
verified
B

You are performing an experiment to assay phosphorylation of a substrate by a protein kinase.Based on the data in the table below, what do these experimental results suggest?

Correct Answer
verified

Correct Answer
verified

Ste5 binds to MAPKKK, MAPKK, and MAPK to organize the kinase cascade.What type of signaling molecule is Ste5?

Correct Answer
verified

A mutation that affects Ca⁺⁺ binding to calmodulin is most likely to interfere with what aspect of a signal transduction pathway?

Correct Answer
verified
B

What is the difference between Ras and the G proteins bound to G protein coupled receptors (GPCRs) ?

Correct Answer
verified

Correct Answer
verified

A mutation in the DNA-binding domain of a steroid hormone receptor is most likely to affect what aspect of receptor function?

Correct Answer
verified

G protein-coupled receptors are the largest family of cell surface receptors.Each receptor passes through the plasma membrane how many times?

Correct Answer
verified

The protein SOS is a guanine nucleotide exchange factor for Ras.SOS helps facilitate the exchange of GDP for GTP.What would be the effect of a mutation that inhibits the interaction between SOS and Ras?

Correct Answer
verified

Correct Answer
verified

In response to injury, cell fragments called platelets get activated to induce clotting.Activated platelets release factors that can in turn bind to specific membrane receptors on nearby cells.What type of signaling would this be considered?

Correct Answer
verified

Some cancers are caused by the overexpression of receptor tyrosine kinases (RTKs) .It is known that RTK signaling pathways commonly stimulate cell division.Why would the overexpression of receptor tyrosine kinases lead to cancer development?

Correct Answer
verified

Some enzymatic receptors and most G protein-coupled receptors transmit the signal into the cytoplasm by utilizing other substances within the cytoplasm that are referred to as:

Correct Answer
verified

Many receptor tyrosine kinase pathways have MAPK as a downstream signaling component.MAPK can phosphorylate target proteins.What type of signaling molecule is MAPK?

Correct Answer
verified

Why are phosphorylation and dephosphorylation reactions commonly used to regulate signal transduction pathways?

Correct Answer
verified

Exam 9: Cell Communication

Correct AnswerverifiedShow Answer

You are planning to perform some protein-protein interaction studies to identify a receptor for a steroid hormone you have been working on.You start by fractionating the cell.What cell fraction would you want to work with to identify the steroid hormone receptor of interest?

Correct AnswerverifiedShow Answer

How are receptor tyrosine kinases and steroid hormone receptors similar?

Correct AnswerverifiedShow Answer

These molecules can directly convert extracellular signals into intracellular signals.

Correct AnswerverifiedC

Correct AnswerverifiedB

You are performing an experiment to assay phosphorylation of a substrate by a protein kinase.Based on the data in the table below, what do these experimental results suggest?

Correct AnswerverifiedShow Answer

Correct AnswerverifiedShow Answer

Ste5 binds to MAPKKK, MAPKK, and MAPK to organize the kinase cascade.What type of signaling molecule is Ste5?

Correct AnswerverifiedShow Answer

A mutation that affects Ca++ binding to calmodulin is most likely to interfere with what aspect of a signal transduction pathway?

Correct AnswerverifiedB

What is the difference between Ras and the G proteins bound to G protein coupled receptors (GPCRs) ?

Correct AnswerverifiedShow Answer

Correct AnswerverifiedShow Answer

A mutation in the DNA-binding domain of a steroid hormone receptor is most likely to affect what aspect of receptor function?

Correct AnswerverifiedShow Answer

G protein-coupled receptors are the largest family of cell surface receptors.Each receptor passes through the plasma membrane how many times?

Correct AnswerverifiedShow Answer

The protein SOS is a guanine nucleotide exchange factor for Ras.SOS helps facilitate the exchange of GDP for GTP.What would be the effect of a mutation that inhibits the interaction between SOS and Ras?

Correct AnswerverifiedShow Answer

Correct AnswerverifiedShow Answer

In response to injury, cell fragments called platelets get activated to induce clotting.Activated platelets release factors that can in turn bind to specific membrane receptors on nearby cells.What type of signaling would this be considered?

Correct AnswerverifiedShow Answer

Some cancers are caused by the overexpression of receptor tyrosine kinases (RTKs) .It is known that RTK signaling pathways commonly stimulate cell division.Why would the overexpression of receptor tyrosine kinases lead to cancer development?

Correct AnswerverifiedShow Answer

Some enzymatic receptors and most G protein-coupled receptors transmit the signal into the cytoplasm by utilizing other substances within the cytoplasm that are referred to as:

Correct AnswerverifiedShow Answer

Many receptor tyrosine kinase pathways have MAPK as a downstream signaling component.MAPK can phosphorylate target proteins.What type of signaling molecule is MAPK?

Correct AnswerverifiedShow Answer

Why are phosphorylation and dephosphorylation reactions commonly used to regulate signal transduction pathways?

Correct AnswerverifiedShow Answer

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C

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B

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A mutation that affects Ca⁺⁺ binding to calmodulin is most likely to interfere with what aspect of a signal transduction pathway?

Correct Answer
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B

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Correct Answer
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