Biology

The correct answer is: B.To facilitate the movement of substances across the membrane

Transport proteins in the cell membrane play a critical role in moving molecules and ions into and out of the cell. These proteins help regulate the movement of substances that cannot pass directly through the lipid bilayer, such as polar molecules, ions, and larger molecules, either through active or passive transport mechanisms.

Here's a breakdown of the options:

A.To provide structural support: This is generally the role of other proteins (like cytoskeletal proteins) and lipid components, not transport proteins.

B.To facilitate the movement of substances across the membrane: This...