Question

within the fluid mosaic of a plasma membrane, what is the role of transport and channel proteins?they are cell - surface connection sites.they identify the cell.they prevent the passage of amino acids.they may set off cellular changes such as cell division or hormone secretion.they permit ions and water molecules to move through the plasma membrane.

Explanation:

Transport and channel proteins are integral membrane proteins. Channel proteins form pores or channels in the membrane, allowing specific ions (e.g., \(Na^{+}\), \(K^{+}\)) and water molecules (in the case of aquaporins, a type of channel protein) to pass through via facilitated diffusion. Transport proteins (carrier proteins) bind to specific molecules (such as glucose) and undergo a conformational change to transport them across the membrane. The other options are incorrect: cell - surface connection sites are usually related to junctional proteins (not transport/channel proteins); cell - identity is often due to glycoproteins (like MHC markers); transport proteins do not prevent amino acid passage (some transport amino acids); and setting off cellular changes like division or hormone secretion is more the role of receptor proteins (e.g., hormone receptors) rather than transport/channel proteins.

Answer:

They permit ions and water molecules to move through the plasma membrane.