Unlike passive transport mechanisms, active transport requires the input of cellular:

• A. oxygen
• B. energy (usually in the form of ATP)
• C. carbon dioxide
• D. water

Answer: (B)

Verified step by step guidance

1. Step 1: Understand the difference between passive and active transport. Passive transport does not require energy and relies on the concentration gradient, while active transport requires energy to move substances against their concentration gradient.
2. Step 2: Recall that active transport mechanisms use energy, typically in the form of ATP (adenosine triphosphate), to power the movement of molecules or ions across the cell membrane.
3. Step 3: Eliminate incorrect options based on the requirements of active transport. Oxygen, carbon dioxide, and water are not directly involved in providing energy for active transport.
4. Step 4: Focus on the correct answer, which is energy (usually in the form of ATP). ATP is the primary energy currency of the cell and is hydrolyzed to provide the necessary energy for active transport processes.
5. Step 5: Relate this concept to biological examples, such as the sodium-potassium pump, which uses ATP to transport sodium ions out of the cell and potassium ions into the cell against their concentration gradients.