Cell signaling (Questions practice)

Question 1

Which of the following is not involved in the specificity of signal transduction?

A) Interactions between receptor and signal molecules
B) Location of receptor molecules
C) Structure of receptor molecules
D) Structure of signal molecules
E) Transmembrane transport of signal molecules by receptor molecules

Answer 1

E) Transmembrane transport of signal molecules by receptor molecules

Question 2

Which of the following is not a feature of signal transduction?

A) Integration of multiple pathways toward the same downstream response
B) Signal amplification
C) Covalent binding between the ligand and the receptor
D) Desensitization or adaptation of the receptor
E) Variable affinity for different signaling components

Answer 2

C) Covalent binding between the ligand and the receptor

Question 3

Scatchard analysis can provide information on:

A) enzyme cascades.
B) enzyme mechanisms.
C) gated ion channels.
D) protein phosphorylation.
E) receptor-ligand interactions.

Answer 3

E) receptor-ligand interactions.

Question 4

Which of the following statements concerning receptor enzymes is correct?

A) They are not usually membrane-associated proteins.
B) They contain an enzyme activity that acts on a cytosolic substrate.
C) They contain an enzyme activity that acts on the extracellular ligand.
D) They have a ligand-binding site on the cytosolic side of the membrane.
E) They have an active site on the extracellular side of the membrane.

Answer 4

B) They contain an enzyme activity that acts on a cytosolic substrate.

Question 5

Which of the following is not one of the general types of signaling mechanisms found in multicellular organisms?

A) Gated ion channels
B) Receptor tyrosine kinases
C) G protein-coupled receptors
D) Receptor cAMP cyclases
E) Adhesion receptors

Answer 5

D) Receptor cAMP cyclases

Question 6

Which of the following is not true for G protein-coupled receptors (GPCRs)?

A) Agonists mimic the effect of the natural ligand.
B) Antagonists block the normal effect of the natural ligand.
C) GPCRs interact with heterodimeric G proteins.
D) GPCRs are have seven transmembrane helices.
E) There exist >100 orphan GPCRs in the human genome with no known ligand.

Answer 6

C) GPCRs interact with heterodimeric G proteins.

Question 7

Cholera and pertussis toxins are:

A) enzyme inhibitors.
B) enzyme modifiers.
C) enzymes.
D) G protein signal transduction disrupters.
E) All of the above

Answer 7

E) All of the above

Question 8

Protein kinase A (PKA) is:

A) activated by covalent binding of cyclic AMP.
B) affected by cyclic AMP only under unusual circumstances.
C) allosterically activated by cyclic AMP.
D) competitively inhibited by cyclic AMP.
E) noncompetitively inhibited by cyclic AMP.

Answer 8

C) allosterically activated by cyclic AMP.

Question 9

Which of the following is not involved in signal transduction by the beta-adrenergic receptor pathway?

A) ATP
B) Cyclic AMP
C) Cyclic GMP
D) GTP
E) All of the above are involved

Answer 9

C) Cyclic GMP

Question 10

Which of the following is not involved in signal transduction by the beta-adrenergic receptor pathway?

A) Cyclic AMP synthesis
B) GTP hydrolysis
C) GTP-binding protein
D) Protein kinase
E) All of the above are involved.

Answer 10

E) All of the above are involved.

Question 11

Which of the following does not bind to heterotrimeric G proteins?

A) GTP-GDP exchange factors (GEFs)
B) GTPase activating proteins (GAPs)
C) GPCRs
D) cGMP
E) GDP

Answer 11

D) cGMP

Question 12

Which of the following are involved in desensitization of the beta-adrenergic receptor?

A) beta-adrenergic receptor kinase
B) Arrestin
C) GTPase activating proteins (GAPs)
D) A and B above
E) A, B, and C above

Answer 12

D) A and B above

Question 13

Which of the following does not use a cAMP-dependent signaling pathway?

A) Insulin
B) Epinephrine
C) Odorants
D) Spicy tastes
E) Growth factors

Answer 13

A) Insulin

Question 14

• Hormone-activated phospholipase C can convert phosphatidylinositol 4,5-bisphosphate to:

A) diacylglycerol + inositol triphosphate.
B) diacylglycerol + inositol+ phosphate.
C) glycerol + inositol + phosphate.
D) glycerol + phosphoserine.
E) phosphatidyl glycerol + inositol + phosphate.

Answer 14

A) diacylglycerol + inositol triphosphate.

Question 15

Calmodulin is a(n):

A) allosteric activator of calcium-dependent enzymes.
B) allosteric inhibitor of calcium-dependent enzymes.
C) calcium-dependent enzyme.
D) cell surface calcium receptor.
E) regulatory subunit of calcium-dependent enzymes.

Answer 15

E) regulatory subunit of calcium-dependent enzymes.

Question 16

Autophosphorylation of receptor tyrosine kinases depends on which of the following?

A) Dimerization of the receptor
B) ATP
C) Ligand binding
D) Transmission of conformational changes through the membrane
E) All of the above

Answer 16

E) All of the above

Question 17

Which of the following statements concerning signal transduction by the insulin receptor is not correct?

A) Activation of the receptor protein kinase activity results in the activation of additional protein kinases.
B) Binding of insulin to the receptor activates a protein kinase.
C) Binding of insulin to the receptor results in a change in its quaternary structure.
D) The receptor protein kinase activity is specific for tyrosine residues on the substrate proteins.
E) The substrates of the receptor protein kinase activity are mainly proteins that regulate transcription.

Answer 17

E) The substrates of the receptor protein kinase activity are mainly proteins that regulate transcription.

Question 18

What is the correct order for the following members of the MAP Kinase cascade?
1) MEK
2) ERK
3) Raf
4) RTK

Answer 18

C) 4, 3, 1, 2

Question 19

Guanyl cyclase receptor enzymes:

A) are all membrane-spanning proteins.
B) are examples of ligand-gated ion channels.
C) catalyze synthesis of a phosphate ester.
D) catalyze synthesis of a phosphoric acid anhydride
E) require hydrolysis of ATP in addition to GTP.

Answer 19

C) catalyze synthesis of a phosphate ester.

Question 20

The ion channel that opens in response to acetylcholine is an example of a ____________ signal transduction system.

A) G-protein
B) ligand-gated
C) receptor-enzyme
D) serpentine receptor
E) voltage-gated

Answer 20

B) ligand-gated

Question 21

Steroid hormones are carried on specific carrier proteins because the hormones:

A) are too unstable to survive in the blood on their own.
B) cannot dissolve readily in the blood because they are too hydrophobic.
C) cannot find their target cells without them.
D) need them in order to pass through the plasma membrane.
E) require subsequent binding to specific receptor proteins in the nucleus.

Answer 21

B) cannot dissolve readily in the blood because they are too hydrophobic.

Question 22

Steriod hormone response elements (HREs) are __________ , which, when bound to _____________, alter gene expession at the level of ________________.

Answer 22

E) sequences in DNA; receptor-hormone complex; transcription

Question 23

Most transduction systems for hormones and sensory stimuli that involve trimeric G proteins have in common all of the following except:

A) cyclic nucleotides.
B) nuclear receptors.
C) receptors that interact with a G protein.
D) receptors with multiple transmembrane segments.
E) self-inactivation.

Answer 23

B) nuclear receptors.

Question 24

The G protein involved in visual signal transduction is:

A) a leukotriene.
B) transducin.
C) arrestin.
D) rhodopsin.
E) a GTP receptor.

Answer 24

B) transducin.

Question 25

Which of the following is not a shared feature of signaling by mammalian vision and gustatory receptor pathways?

A) Changes in cAMP levels
B) GDP/GTP exchange
C) Heterotrimeric G proteins
D) Open/closing of ion channels
E) Transmembrane receptors

Answer 25

A) Changes in cAMP levels

Question 26

Which of the following statements concerning cyclin-dependent protein kinases is not correct?

A) Each type of cell contains one specific form (isozyme).
B) Their activity fluctuates during the cell cycle.
C) Their activity is regulated by changes in gene expression, protein phosphorylation, and proteolysis.
D) Their activity is regulated by cyclins.
E) They can alter the activity of proteins involved in the progression of cells through the cell cycle.

Answer 26

A) Each type of cell contains one specific form (isozyme).

Question 27

Which of the following statements concerning cyclins is not correct?

A) They are activated and degraded during the cell cycle.
B) They are regulatory subunits for enzymes that catalyze the phosphorylation of proteins.
C) They can become linked to ubiquitin.
D) They catalyze the phosphorylation of proteins.
E) They contain specific amino acid sequences that target them for proteolysis.

Answer 27

D) They catalyze the phosphorylation of proteins.

Question 28

Ubiquitin is a:

A) component of the electron transport system.
B) protease.
C) protein kinase.
D) protein phosphorylase.
E) protein that tags another protein for proteolysis.

Answer 28

E) protein that tags another protein for proteolysis.

Question 29

Cyclin-dependent protein kinases can regulate the progression of cells through the cell cycle by phosphorylation of proteins such as:

A) insulin.
B) myoglobin.
C) myosin.
D) retinal rod and cone proteins.
E) All of the above

Answer 29

C) myosin.

Question 30

Proto-oncogenes can be transformed to oncogenes by all of the following mechanisms except:

A) chemically induced mutagenesis.
B) chromosomal rearrangements.
C) during a viral infection cycle.
D) elimination of their start signals for translation.
E) radiation-induced mutation.

Answer 30

D) elimination of their start signals for translation.

Question 31

Oncogenes are known that encode all of the following except:

A) cytoplasmic G proteins and protein kinases.
B) DNA-dependent RNA polymerases.
C) growth factors.
D) secreted proteins.
E) transmembrane protein receptors.

Answer 31

B) DNA-dependent RNA polymerases.

Question 32

Mutations in which of the following are not part of the progression from normal to cancerous cells in colorectal cancer?

A) Abl involved in cellular signaling
B) KRAS and BRAF kinases involved in cellular signaling
C) PI3K and PTEN involved in cellular signaling
D) MMR involved in DNA repair
E) CDC4 involved in ubiquitination

Answer 32

A) Abl involved in cellular signaling