Which of the following is not required for osmosis to occur?

• A. Water molecules
• B. A semipermeable membrane
• C. Energy input
• D. A concentration gradient

Answer: (C)

Verified step by step guidance

1. Understand the concept of osmosis: Osmosis is the movement of water molecules through a semipermeable membrane from a region of lower solute concentration to a region of higher solute concentration.
2. Identify the components necessary for osmosis: Water molecules are essential as they are the ones moving. A semipermeable membrane is required to allow only certain molecules to pass through, and a concentration gradient is needed to drive the movement of water.
3. Recognize that osmosis is a passive process: It does not require an external energy input. Instead, it relies on the natural kinetic energy of water molecules and the concentration gradient.
4. Evaluate the options given: Water molecules, a semipermeable membrane, and a concentration gradient are all necessary for osmosis to occur.
5. Conclude that energy input is not required for osmosis: Since osmosis is a passive process, it does not need additional energy to take place.