Chapter 11- Cell Communication

Question 1

Binding of a signaling molecule to which type of receptor leads directly to a change in the distribution of ions on opposite sides of the membrane?
A. Intercellular receptor
B. G protein-coupled receptor
C. Phosphorylated receptor tyrosine kinase dimer
D. Ligand-gated ion channel

Answer 1

D. Ligand-gated ion channel

Question 2

The activation of receptor tyrosine kinases is characterized by
A. Dimerization and phosphorylation. 
B. Dimerization and IP3 binding. 
C. A phosphorylation cascade. 
D. GTP hydrolysis.

Answer 2

A. Dimerization and phosphorylation

Question 3

Lipid-soluble signaling molecules, such as aldosterone, cross the membranes of all cells but affect only target cells because
A. Only target cells retain the appropriate DNA segments.
B. Intracellular receptors are present only in target cells.
C. Only target cells retain have enzymes that break down aldosterone.
D. Only in target cells is aldosterone able to initiate the phosphorylation cascade that turns genes.

Answer 3

B. Intracellular receptors are present only in target cells.

Question 4

Consider this pathway: epinephrine-> G protein-> adenylyl cyclase-> cAMP. Identify the second messenger. 
A. cAMP
B. G protein
C. GTP
D. Adenylyl cyclase

Answer 4

A. cAMP

Question 5

Apoptosis involves all but which of the following
A. Fragmentation of the DNA
B. cell-signaling pathways
C. Lysis of the cell.
D. Digestion of cellular contents by scavenger cells.

Answer 5

C. Lysis of the cell.

Question 6

Which observation suggested to Sutherland the involvement of a second messenger in epinephrine’s effect on liver cells?
A. Enzymatic activity was proportional to the amount of calcium added to a cell-free extract.
B. Receptor studies indicated that epinephrine was a ligand.
C. Glycogen breakdown was observed only when epinephrine was administered to intact cells
D. Glycogen breakdown was observed when epinephrine and glycogen phosphorylase were combined.

Answer 6

C. Glycogen breakdown was observed only when epinephrine was administered to intact cells

Question 7

Protein phosphorylation is commonly involved with all of the following except
A. Activation of receptor tyrosine kinases.
B. Activation of protein kinase molecules.
C. Activation of G protein-coupled receptors.
D. Regulation of transcription by signaling molecules.

Answer 7

C. Activation of G protein-coupled receptors.