Which of the following processes includes all of the others?

• A. Osmosis
• B. Facilitated diffusion
• C. Passive transport
• D. Transport of an ion down its electrochemical gradient

Answer: (C)

Verified step by step guidance

1. Begin by understanding the concept of passive transport. Passive transport is a type of cellular transport where substances move across cell membranes without the need for energy input. It relies on the concentration gradient of the substances.
2. Identify the processes listed: osmosis, facilitated diffusion, and transport of an ion down its electrochemical gradient. All these processes are types of passive transport.
3. Osmosis is the movement of water molecules through a selectively permeable membrane from an area of higher water concentration to an area of lower water concentration. It is a specific type of passive transport.
4. Facilitated diffusion involves the movement of molecules across cell membranes through protein channels or carriers. It allows substances that cannot directly diffuse through the lipid bilayer to move down their concentration gradient.
5. Transport of an ion down its electrochemical gradient refers to the movement of ions across a membrane driven by both concentration and electrical gradients. This is also a form of passive transport, as it does not require energy input.