Active transport requires cellular energy

Steps:

• Identify processes involving molecule movement across membranes.
• Distinguish between passive (no energy) and active (energy needed) transport.
• Recall respiration provides ATP for active transport.
• Match options to transport types: diffusion is passive, uptake against gradient is active.

Why C is correct:

• Uptake of glucose by cells often uses active transport (e.g., via GLUT transporters with sodium-glucose symporters), requiring ATP from respiration per the definition of active transport as movement against concentration gradients.

Why the others are wrong:

• A: Carbon dioxide diffusion into alveoli is passive, following its concentration gradient without energy.
• B: Oxygen binding to hemoglobin in red blood cells is passive dissolution, not requiring respiration energy.
• D: Water uptake by root cells via osmosis is passive, driven by water potential differences.

Final answer: C