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

• A. Active transport proteins
• B. Water molecules
• C. A difference in solute concentration across the membrane
• D. A semipermeable membrane

Answer: (A)

Verified step by step guidance

1. Step 1: Understand the definition of osmosis. Osmosis is the movement of water molecules across a semipermeable membrane from a region of lower solute concentration to a region of higher solute concentration.
2. Step 2: Identify the essential components for osmosis: (a) water molecules must be present to move, (b) there must be a difference in solute concentration across the membrane to create a concentration gradient, and (c) a semipermeable membrane is required to allow only water molecules (not solutes) to pass through.
3. Step 3: Recognize that osmosis is a passive process driven by concentration gradients and does not require energy input or active transport proteins.
4. Step 4: Analyze the options given: Active transport proteins are involved in moving substances against their concentration gradient using energy, which is not necessary for osmosis.
5. Step 5: Conclude that the component NOT required for osmosis to occur is active transport proteins, since osmosis relies solely on passive movement of water through a semipermeable membrane driven by solute concentration differences.