In which type of absorption does a carrier protein move a molecule without additional energy?

• A. Passive Diffusion.
• B. Facilitated Diffusion.
• C. Active Transport.
• D. Exocytosis.

Answer: (B)

Verified step by step guidance

1. Understand the types of absorption mechanisms: Passive Diffusion, Facilitated Diffusion, Active Transport, and Exocytosis. Each has distinct characteristics.
2. Passive Diffusion involves the movement of molecules across a membrane from a region of higher concentration to lower concentration without the need for energy or a carrier protein.
3. Facilitated Diffusion also moves molecules from higher to lower concentration, but it requires a carrier protein to assist in the process. Importantly, no additional energy (ATP) is required.
4. Active Transport moves molecules against their concentration gradient (from lower to higher concentration) and requires both a carrier protein and energy in the form of ATP.
5. Exocytosis is a process where cells expel materials using vesicles, which is unrelated to the movement of molecules across a membrane via carrier proteins. Based on this, the correct answer is Facilitated Diffusion.