Active transport requires respiratory energy

Steps:

• Respiration produces ATP, the energy source for active transport against concentration gradients.
• Evaluate each option: passive processes like diffusion and osmosis need no energy.
• Identify active transport: glucose uptake in villi uses carrier proteins to move glucose against its gradient.
• Confirm: only option C matches active transport needing ATP from respiration.

Why C is correct:

• Glucose uptake by villi cells is active transport, defined as movement against a concentration gradient using ATP from cellular respiration.

Why the others are wrong:

• A: Carbon dioxide movement into alveoli is passive diffusion down its partial pressure gradient.
• B: Oxygen entry into red blood cells is passive diffusion across the membrane.
• D: Water uptake by root cells is osmosis, a passive process following the water potential gradient.

Final answer: C