Exam (elaborations) BIOCHEM CHAPTER 12

BIOCHEM CH. 12 EXAM 12
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 - CORRECT
ANSWER-Transmembrane transport of signal molecules by receptor molecules

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 - CORRECT ANSWER-C)
Covalent binding between the ligand and the receptor

Scatchard analysis can provide information on:

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

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

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 - CORRECT ANSWER-D) Receptor cAMP cyclases

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. -
CORRECT ANSWER-C) GPCRs interact with heterodimeric G proteins.

Cholera and pertussis toxins are:

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

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. - CORRECT ANSWER-C) allosterically
activated by cyclic AMP.

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. - CORRECT ANSWER-C) Cyclic GMP

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

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