Chapter 11 Multiple Choice Questions

Question 1

Phosphorylation cascades involving a series of protein kinases are useful for cellular signal transduction because
A) They are always species specific
B) They always lead to the same cellular response
C) They amplify the original signal many-fold
D) The counter the harmful effects of phosphates

Answer 1

C) The amplify the original signal manyfold

Question 2

Binding of a signal molecule to which type of receptor leads directly to a change in the distribution of anions and/or cations on opposite sides of the membrane?
A) Receptor tyrosine kinase
B) G-Protein-linked receptor
C) Phosphorylated receptor tyrosine kinase dimer
D) Ligand- gated ion channel
E) Intracellular receptor

Answer 2

D) Ligand- gated ion channel

Question 3

The activation of receptor tyrosine kinases is always characterized by
A) Dimerization and phosphorylation
B) IP3 binding
C) A phosphorylation cascade
D) GTP hydrolysis
E) Channel protein conformational change

Answer 3

A) Dimerization and phosphorylation

Question 4

Which of the following provides the best evidence that cell-signaling pathways evolved early in the history of life?
A) They are seen in “primitive” cells such as yeast cells
B) Yeast cells signal each other for mating
C) Signal transduction molecules found in distantly related organisms are similar
D) Signals can be sent long distances
E) Most signals are recieved by cell surface receptors

Answer 4

C) Signal transduction molecules found in distantly related organisms are similar

Question 5

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
E) Epinephrine was known to have different effectss on different types of cells

Answer 5

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

Question 6

Protein phosphorylation is commonly involved with all of the following except
A) Regulation of transcription by extra-cellular signal molecules
B) Enzyme activation
C) Activation of G-protein lined receptors
D) Activation of receptor tyrosine kinases
E) Activation of protein kinase molecules

Answer 6

C) Activation of G-protein lined receptors

Question 7

Amplification of a chemical signal occurs when
A) A receptor in the plasma membrane activates several G-protein molecules while a signal is bound to it.
B) A cAMP molecule activates one protein kinase molecule before being converted to AMP
C) Phosphorylase and phosphatase activities are balanced
D) Receptor tyrosine kinases dimerize upon ligan bonding
E) both A and D occur

Answer 7

A) A receptor in the plasma membrane activates several G-protein molecules while a signal is bound to it.

Question 8

Lipid soluble signal molecules, such as testosterone, cross the membranes of all cells but only affect target cells because
A) Only target cells retain the appropriate DNA segments
B) Intracellular receptors are present only in target cells
C) Most cells lack the Y chromosome required
D) Only target cells possess the cytosolic enzymes that transduce the testosterone
E) Only in target cells is testosterone able to initiate the phosphorylation cascade leading to the activated tracscription factor

Answer 8

B) Intracellular receptors are present only in target cells