Active Transport Characteristics

Steps:

• Recall active transport moves ions/molecules against their concentration gradient using carrier proteins.
• Confirm it requires ATP energy input, unlike passive processes.
• Note it occurs across cell membranes via specific channels or pumps.
• Compare options: identify the row with ✓ for against gradient, through membrane, and energy; × for down gradient.

Why D is correct:

• Matches definition: active transport goes against gradient (✓), not down (×), crosses membrane (✓), and needs energy (✓).

Why the others are wrong:

• A: All × ignores energy requirement and against-gradient movement.
• B: × for against gradient and energy; active transport isn't passive.
• C: ✓ only for down gradient; active transport opposes this.

Final answer: D