Question

Which of the following statements is TRUE?

1) Gap junctions are large pores that connect the cytosol to the extracellular space.
2) Aquaporin channels are found in the plasma membrane, allowing the rapid passage of water molecules and small ions in and out of cells.
3) The ion selectivity of a channel completely depends solely on the charge of the amino acids lining the pore inside the channel.

Answer 1

The true statement is the second one, which says aquaporin channels in the plasma membrane allow for the rapid passage of water molecules. Gap junctions connect adjacent animal cells, not the cytoplasm to extracellular space, and ion selectivity depends on multiple factors.

Step-by-step explanation:

The correct statement among the ones provided is the second one, stating that aquaporin channels are found in the plasma membrane and allow rapid passage of water molecules. These channel proteins facilitate water movement across cell membranes but do not typically allow ions to pass through. The first statement is incorrect because gap junctions are protein-lined pores that connect the cytoplasm of adjacent animal cells, not the cytoplasm to extracellular space.

Lastly, the third statement is also untrue; the ion selectivity of a channel depends on more factors than just the charge of the amino acids lining the pore. This may include the size and shape of the ion, as well as the specific properties of the channel protein.