Question

what is an aquaporin?
a membrane protein that is linked to an enzyme
a protein network that blocks fluid movement
a membrane protein that contains a channel for water movement
a glycoprotein that identifies the cell

Explanation:

Aquaporins are membrane - spanning proteins that form channels in the membrane, specifically allowing water molecules to pass through. They are not linked to enzymes, do not block fluid movement, and are not glycoproteins for cell - identification.

Answer:

a membrane protein that contains a channel for water movement