What is mediated transport in the context of membrane transport?

• A. The active transport of ions using energy from ATP.
• B. The movement of molecules across a membrane without the aid of proteins.
• C. The movement of molecules across a membrane with the help of transport proteins.
• D. The passive diffusion of water molecules through a semipermeable membrane.

Answer: (C)

Verified step by step guidance

1. Understand the concept of mediated transport: Mediated transport refers to the movement of molecules across a cell membrane with the assistance of transport proteins. These proteins facilitate the transport of substances that cannot pass through the lipid bilayer directly.
2. Differentiate between types of transport: Recognize that mediated transport can be either active or passive. Active transport requires energy, often from ATP, to move molecules against their concentration gradient, while passive transport does not require energy and moves molecules along their concentration gradient.
3. Identify the role of transport proteins: Transport proteins are integral membrane proteins that assist in the movement of substances across the cell membrane. They can be channels, carriers, or pumps, each serving specific functions in transporting molecules.
4. Consider examples of mediated transport: Examples include facilitated diffusion, where transport proteins help move substances passively, and active transport, where proteins like pumps use energy to transport ions or molecules.
5. Clarify misconceptions: Ensure understanding that mediated transport involves proteins, distinguishing it from simple diffusion, which does not involve proteins, and osmosis, which specifically refers to the passive diffusion of water.