PRACTICE QUESTIONS

1. Increasing the extracellular K^- concentration will:

a. Have no effect on the resting membrane potential.

b. Cause the resting membrane potential to decrease (i.e., cause the inside to become less negative with respect to the outside).

c. Cause the resting membrane potential to increase (i.e., cause the inside to become more negative with respect to the outside).

d. Increase the concentration potential for K^t across the plasma membrane.

e. Require the Na,K^, pump to work harder to pump K^t.

2. G proteins are similar to receptors in that both:

a. Bind extracellular signaling molecules.

b. Interact directly with adenylyl cyclase catalytic sub­units.

c. Have activated and inactivated states dependent on ligand binding.

d. Are extracellular protein molecules.

e. Directly activate a protein kinase activity.

3. Which of the following statements concerning intra­cellular Ca^2, is false?

a. It is a second messenger for hormones and neuro­transmitters.

b. It is responsible for excitation-contraction coupling in smooth muscle.

c. An increase in its concentration in a nerve terminal stimulates the release of a neurotransmitter.

d. It activates protein kinase A.

e. Its concentration is increased in the presence ofIP_i.

4. If, in a particular capillary bed, the plasma oncotic pres­sure were to increase and hydrostatic pressure remained constant:

a. More blood plasma would filter from the capil­laries.

b. The transport effect would be similar to decreasing hydrostatic pressure.

c. One would suspect a deficiency in blood protein levels.

d. One would suspect an increase in extracellular fluid protein concentrations.

e. Fluid reabsorption on the venous side of the capillary bed would decline.

5. Substance X is found to be at a much higher concen­tration on the outside of a cell than in the cytoplasm, but no transport of X from the extracellular fluid to the cytoplasm occurs. Which of the following statements is inconsistent with this situation?

a. Substance X has the same electrochemical potential outside and inside the cell.

b. Substance X is large, is poorly soluble in oil, and has no transport proteins in the membrane.

c. Substance X is an ion, and the measured membrane potential is the equilibrium potential calculated by the Nernst equation.

d. Substance X is a steroid molecule.

e. Substance X is actively transported from the cell to the extracellular fluid.