Question

1) In contrast to transporters, channel proteins in cellular membranes …

interact strongly with the solute(s) that they transport.

undergo a conformational change every time they transport a solute.

can only mediate passive transport.

form pores that are always open.

are always controlled by voltage

2) A neuron’s repetitive firing rate is limited by an absolute refractory period, during which a new action potential cannot be generated. Which event is chiefly responsible for this limit?

Opening of K+ leak channels.

Opening of voltage-gated Na+ channels.

Opening of transmitter-gated cation channels.

Inactivation of voltage-gated K+ channels.

Inactivation of voltage-gated Na+ channels.

Answer 1

Answer

1) In contrast to transporters, channel proteins in cellular membranes

• can only mediate passive transport.

- Channel proteins carry solutes along their concentration gradient and are always passive.
- They can always remain open or may open and close depending on the needs of the cell.

Option C

2) A neuron’s repetitive firing rate is limited by an absolute refractory period, during which a new action potential cannot be generated. The event chiefly responsible for this limit is :

• Inactivation of voltage-gated Na+ channels

- Neuron cannot generate new action potentia because Na+ channels are innactive.

Option E