quiz 11/12

K+ leak channels are found in the plasma membrane. These channels open and close in an unregulated, random fashion. What do they accomplish in a resting cell? a.They set the K+ concentration gradient to zero. b.They keep the electrochemical gradient for K+ at zero. c.They set the membrane potential to zero. d.They disrupt the resting membrane potential.

b.They keep the electrochemical gradient for K+ at zero.

If Na+ channels are opened in a cell that was previously at rest, how will the resting membrane potential be affected?

it becomes more positive

Proteins that are associated with the membrane by noncovalent interactions with other membrane proteins are called ___________ proteins.

peripheral membrane

Lipid bilayers are highly impermeable to which molecule(s)?

Na+ and Cl-

The movement of an ion against its concentration gradient is called what?

active transport

Which term correctly describes the entire phospholipid molecule?

amphipathic

In a lipid bilayer, where do lipids rapidly diffuse? a. back and forth from one monolayer to the other in the bilayer b. within the plane of their own monolayer c. within the plane of one monolayer and back and forth between the monolayers d. in and out of the bilayer e. not at all, because they remain in place within the bilayer

b. within the plane of their own monolayer

Which of the following would yield the most highly mobile phospholipid (listed as number of carbons and number of double bonds, respectively)? a.16 carbons with no double bonds b.15 carbons with two double bonds c.20 carbons with two double bonds d.24 carbons with one double bond

b.15 carbons with two double bonds

In the α helices of single-pass transmembrane proteins, the hydrophobic side chains face which direction? a. the external or lumenal side of the membrane b. the inside of the membrane-spanning helix c. the outside of the membrane-spanning helix d. the cytosolic side of the membrane

c. the outside of the membrane-spanning helix

Which of the following is most likely to occur after the lipid bilayer is pierced? a.The membrane collapses. b.The membrane expands. c.The membrane reseals. d.A tear is formed.

c.The membrane reseals.

Transporters, in contrast to channels, work by a.filtering solutes by charge. b.a gating mechanism. c.specific recognition of transport substrates. d.filtering solutes by size.

c.specific recognition of transport substrates.

Plasma membrane proteins that move ions in and out of cells using passive transport are called

channels

Which of the following substances is most commonly used to help purify a membrane protein?

detergent