Question

What are the aquaporins in the facilitated diffusion process?
A. Membrane proteins
B. Carrier proteins
C. Channel proteins
D. Carrier lipids

Answer 1

Hint: Aquaporins are found in the cell membrane. These are channels that allow the movement of water rapidly across the membrane. They prevent solutes from penetrating the membrane and also prevent the passage of certain ions.

Complete answer: Aquaporins are channels that allow the movement of water molecules across the cell membrane at a very fast rate, they are the integral membranes of the pore proteins and selectively conduct water molecules in and out of the cell. It also prevents the passage of ions and other solutes during the time of diffusion. The facilitated diffusion is a diffusion of the solutes which is transported through proteins in the plasma membrane. It is a passive transport as the solute moves down the concentration gradient. The small nonpolar diffuse easily across the cell membranes but the polar molecules cannot diffuse through the cell membrane as the cell membrane are made up of the lipids which are hydrophobic in nature. These polar molecules are then transported with the help of the transport protein which allows these molecules to diffuse across the cell membranes. The channel proteins which are a type of transport protein which acts as a pore in the membrane which allows the polar ions to pass. These water channels proteins are aquaporins which allow the diffusion of the water molecules at a very fast rate.
Hence, the correct answer is option C.

Note: Aquaporins are channel proteins from a larger family of major intrinsic proteins. Peter Agre won the 2003 “Nobel prize” for the discovery of aquaporins. Genetic defects involving aquaporin genes have been associated with several human diseases including nephrogenic diabetes insipidus and neuromyelitis optica.