Chapter 15

Question 1

What type of signaling is also known as hormones?

Answer 1

Endocrine Signaling

Question 2

Activation of this receptor by circulating adrenaline leads to glycogen breakdown in a liver cell and relaxation in a smooth muscle cell.

Answer 2

β2-adrenergic receptor

Question 3

Which of the following is an inherited disorder traced to defects in G Protein-couple Receptors (GPCR) that leads to progressive degeneration of the retina and eventual blindness?

Answer 3

Retina Pigmentosa

Question 4

The mutation that causes thyroid adenomas is found in the tumor tissue and was not inherited.

Answer 4

True

Question 5

What was the first acive GPCR to show x-ray crystal structure with it’s bound G protein?

Answer 5

Rhodopsin Receptor

Question 6

The second messenger, was identified by Earl Sutherland, and is said to be the beginning of the study of signal transduction.

Answer 6

cAMP

Question 7

When the neurotransmitter acetylcholine binds to the surface of a smooth muscle cell within the wall of the stomach, the muscle cell is stimulated to contract. When a foreign antigen binds to the surface of a mast cell, the cell is stimulated to secrete histamine, a substance that can trigger the symptoms of an allergy attack. Both of these responses, one leading to contraction and the other to secretion, are triggered by the same second messenger. Which second messenger is being discussed?

Answer 7

Phosphaidylinositol

Question 8

The cAMP response element is what particular nucleotide sequence?

Answer 8

TGACGTCA

Question 9

Absorption of a single photon of light induces a conformational change in the rhodopsin molecule, which transmits a signal to a heterotrimeric G protein which activates a coupled effector. The G protein is which of the following?

Answer 9

Transducin

Question 10

Taste receptor cells that elicit the taste of umami respond to the amino acids aspartate and glutamate and to purine nucleoides generating a perception that a food is __________?

Answer 10

Savory

Question 11

Which amino acids are known to be phosphorylated by protein kinases?

Answer 11

serine, threonine, tyrosine

Question 12

Which of the following is (are) not characteristics of the pathways activated by second messengers?

Answer 12

Each protein in the pathway typically acts by altering the conformation of the previous (upstream) protein in the series, an event that activates or inhibits the protein.

Question 13

Place the events below in the correct order.

1) G protein binds to activated receptor forming a receptor-G protein complex
2) Release of GDP by the G protein
3) Change in conformation of the cytoplasmic loops of the receptor
4) Binding of GTP by the G protein
5) Increase in the affinity of the receptor for a G protein on the cytoplasmic surface of the membrane.
6) Binding of a hormone or neurotransmitter to a G-protein coupled receptor
7) Conformational shift in the α-subunit of the G protein

Answer 13

6 – 3 – 5 – 1 – 7 – 2 – 4

Question 14

Cell signaling makes it possible for __________.
A. various cells to work together and coordinate their activities
B. cells to respond in an appropriate manner to a specific environmental stimulus
C. all of these answers are correct
D.cells to closely regulate their growth and division

Answer 14

All

Question 15

What allows cells to respond to an extracellular messenger molecule?

Answer 15

They must express receptors that specifically recognize and bind that particular messenger molecule.

Question 16

What is a second messenger?
A. A substance that reacts with a first messenger.
B. A substance released into the intracellular space.
C. A substance that reacts with a hormone or other ligand.
D. None of these is the correct answer.

Answer 16

None

Question 17

Which of the following is (are) characteristic of the pathways activated by second messengers?
A. Some pathway phosphatases and protein kinases have numerous proteins as their substrates; others act on only a single protein substrate or a single amino acid of a protein substrate.
B. Each signaling pathway consists of a series of distinct proteins that operate in sequence.
C. Alterations in signaling protein conformations are often accomplished by protein kinases and protein phosphatases that, respectively, add or remove phosphate groups from other proteins.
D. All of these answers are correct.

Answer 17

All

Question 18

Which of the following are natural ligands that bind to G-protein coupled receptors?
A. opium derivatives 
B. odorants and tastants 
C. all of these are correct answers 
D. photons

Answer 18

All

Question 19

What is the role of G proteins in a signaling pathway?
A. They act as a switch to turn activities on and off.
B. All of these answers are correct.
C. They interact with GTP.
D. They interact with receptors, and stimulate cellular activities.

Answer 19

All

Question 20

What happens to cells if the receptors are degraded once they are internalized?

Answer 20

The cells lose, at least temporarily, sensitivity for the ligand in question.