Which statement best describes the difference between active transport and passive transport?

• A. Active transport requires energy, while passive transport does not.
• B. Passive transport requires ATP, while active transport does not.
• C. Active transport only occurs in animal cells, while passive transport occurs in plant cells.
• D. Passive transport moves substances against their concentration gradient, while active transport moves them along the gradient.

Answer: (A)

Verified step by step guidance

1. Understand the basic definitions: Active transport is the movement of molecules across a cell membrane from a region of lower concentration to a region of higher concentration, requiring energy, usually in the form of ATP. Passive transport is the movement of molecules across a cell membrane from a region of higher concentration to a region of lower concentration, without the use of energy.
2. Identify the role of energy: Active transport requires energy because it moves substances against their concentration gradient, which is from low to high concentration. In contrast, passive transport does not require energy as it moves substances along their concentration gradient, from high to low concentration.
3. Consider the types of cells involved: Both active and passive transport can occur in various types of cells, including both animal and plant cells. Therefore, the statement that active transport only occurs in animal cells and passive transport in plant cells is incorrect.
4. Examine the direction of movement: Passive transport moves substances along the concentration gradient (high to low), while active transport moves substances against the concentration gradient (low to high).
5. Evaluate the statements: The correct statement is that active transport requires energy, while passive transport does not. This is because active transport moves substances against their concentration gradient, necessitating energy input, whereas passive transport moves substances along the gradient without energy.