Cell Membrane & Transport, Receptors & Messengers

Question 1

What’s the difference between steady state and equilibrium?

Answer 1

Steady state requires energy of Na/K ATPase pump to offset the leak of Na in and K out of the cell.
Equilibrium does NOT require energy - passive distribution of ions/substances.

Question 2

What powers facilitated transport? Example?

Answer 2

DIFFUSION - no energy required. It’s the movement of a substance through a transmembrane protein down the substance’s gradient. Example - glucose

Question 3

On which side of the cell are Na/K ATPase proteins located?

Answer 3

RULE: Na/K ATPase is only on the basolateral membrane (the side away from the lumen).

Question 4

How long does it take for the total membrane of a cell to turn over? Why does it do this?

Answer 4

Takes about an hour - this rate accounts for the ability to reconfigure the type of proteins (channels, transporters, receptors, etc) in the membrane in relatively short order.

Question 5

What’s the most important second-messenger system?

Answer 5

cAMP

Question 6

How can cAMP have such diverse mechanisms of action within a cell?

Answer 6

cAMP diffuses throughout the cell to bind to cAMP-dependent kinases (PKA), and PKA phosphorylates a variety of enzymes throughout the cytosol

Question 7

What are two second messengers derived from plasma membrane phospholipids?

Answer 7

• -IP3, DAG (formed by action of phospholipase C on PIP2)

- -Arachidonic acid (formed by action of phospholipase A2 on membrane phospholipids)

Question 8

Name the second messenger and the kinase associated with:

adenylyl cyclase

Answer 8

cAMP

protein kinase A

Question 9

Name the second messenger and the kinase associated with:

guanylyl cyclase

Answer 9

cGMP

protein kinase G

Question 10

Name the second messenger and the kinase associated with:

phospholipase C

Answer 10

IP3 (regulating calcium), DAG

protein kinase C

Question 11

Name the second messenger and the kinase associated with:

phospholipase A2

Answer 11

arachidonic acid

cyclooxygenase, lipoxygenase

Question 12

Which of the following processes directly utilizes ATP?
A. facilitated diffusion
B. primary active transport
C. secondary active transport
D. all require ATP

Answer 12

B. only primary active transport utilizes ATP

Question 13

The fastest axonal conduction speeds are reserved for:
A. somatic efferents and afferents
B. autonomic efferents
C. visceral afferents

Answer 13

A. somatic efferents and afferents

Autonomic efferents are largely unmyelinated