K–12 Biology Practice Questions — Part 2
Questions 21–40
21. Which process allows water molecules to move across a selectively permeable
membrane?
A. Diffusion
B. Osmosis
C. Active transport
D. Endocytosis
Answer: B. Osmosis
Explanation: Osmosis is the movement of water molecules across a selectively permeable
membrane from an area of higher water concentration to an area of lower water concentration.
22. A cell is placed in a solution with a higher solute concentration than the cell. What will
most likely happen?
A. Water enters the cell
B. Water leaves the cell
C. Solute leaves the cell
D. The cell immediately divides
Answer: B. Water leaves the cell
Explanation: The surrounding solution is hypertonic relative to the cell. Water moves out of the
cell by osmosis toward the area with the higher solute concentration.
23. Which type of transport requires cellular energy in the form of ATP?
A. Simple diffusion
B. Osmosis
C. Active transport
D. Facilitated diffusion
Answer: C. Active transport
Explanation: Active transport requires energy because substances are moved against their
concentration gradient, usually from an area of lower concentration to an area of higher
concentration.
24. Which structure controls what enters and leaves a cell?
A. Cell wall
B. Cytoplasm
, C. Cell membrane
D. Nucleus
Answer: C. Cell membrane
Explanation: The cell membrane is selectively permeable. It regulates the movement of
substances into and out of the cell.
25. Which process moves molecules from an area of high concentration to an area of low
concentration without requiring ATP?
A. Active transport
B. Diffusion
C. Endocytosis
D. Exocytosis
Answer: B. Diffusion
Explanation: Diffusion is the passive movement of particles down their concentration gradient.
Because the movement does not require cellular energy, it is considered passive transport.
26. Facilitated diffusion differs from simple diffusion because facilitated diffusion:
A. Requires ATP
B. Moves substances against the concentration gradient
C. Uses membrane proteins
D. Occurs only in plant cells
Answer: C. Uses membrane proteins
Explanation: Facilitated diffusion is passive transport, but substances move through specific
membrane proteins such as channels or carrier proteins.
27. A plant cell placed in a hypotonic solution will most likely:
A. Lose water and shrink
B. Gain water and become firm
C. Lose its cell wall
D. Stop using energy
Answer: B. Gain water and become firm
Explanation: Water enters the plant cell through osmosis. The cell wall prevents excessive
expansion, producing a firm or turgid cell.
Questions 21–40
21. Which process allows water molecules to move across a selectively permeable
membrane?
A. Diffusion
B. Osmosis
C. Active transport
D. Endocytosis
Answer: B. Osmosis
Explanation: Osmosis is the movement of water molecules across a selectively permeable
membrane from an area of higher water concentration to an area of lower water concentration.
22. A cell is placed in a solution with a higher solute concentration than the cell. What will
most likely happen?
A. Water enters the cell
B. Water leaves the cell
C. Solute leaves the cell
D. The cell immediately divides
Answer: B. Water leaves the cell
Explanation: The surrounding solution is hypertonic relative to the cell. Water moves out of the
cell by osmosis toward the area with the higher solute concentration.
23. Which type of transport requires cellular energy in the form of ATP?
A. Simple diffusion
B. Osmosis
C. Active transport
D. Facilitated diffusion
Answer: C. Active transport
Explanation: Active transport requires energy because substances are moved against their
concentration gradient, usually from an area of lower concentration to an area of higher
concentration.
24. Which structure controls what enters and leaves a cell?
A. Cell wall
B. Cytoplasm
, C. Cell membrane
D. Nucleus
Answer: C. Cell membrane
Explanation: The cell membrane is selectively permeable. It regulates the movement of
substances into and out of the cell.
25. Which process moves molecules from an area of high concentration to an area of low
concentration without requiring ATP?
A. Active transport
B. Diffusion
C. Endocytosis
D. Exocytosis
Answer: B. Diffusion
Explanation: Diffusion is the passive movement of particles down their concentration gradient.
Because the movement does not require cellular energy, it is considered passive transport.
26. Facilitated diffusion differs from simple diffusion because facilitated diffusion:
A. Requires ATP
B. Moves substances against the concentration gradient
C. Uses membrane proteins
D. Occurs only in plant cells
Answer: C. Uses membrane proteins
Explanation: Facilitated diffusion is passive transport, but substances move through specific
membrane proteins such as channels or carrier proteins.
27. A plant cell placed in a hypotonic solution will most likely:
A. Lose water and shrink
B. Gain water and become firm
C. Lose its cell wall
D. Stop using energy
Answer: B. Gain water and become firm
Explanation: Water enters the plant cell through osmosis. The cell wall prevents excessive
expansion, producing a firm or turgid cell.
