Biology

The correct answer is D.Proteins.

Explanation:

The channels and pumps in the cell membrane are made of proteins. These proteins are embedded in the lipid bilayer of the membrane and facilitate the movement of materials, such as ions, nutrients, and waste products, across the membrane.

1.Channel proteins form pores that allow certain molecules or ions to pass through the membrane passively (e.g., through facilitated diffusion).

2.Pump proteins use energy (usually ATP) to move substances actively against their concentration gradients (e.g., the sodium-potassium pump).

Why the other options are incorrect:

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