Movement of Substances

Question 1

What is diffusion?

Answer 1

Diffusion is the net movement of ions or molecules from a region of higher concentration to a region of lower concentration, down a concentration gradient.

Question 2

What is osmosis?

Answer 2

Osmosis is the net movement of water molecules from a solution of higher water potential to a solution of lower water potential, through a partially permeable membrane.

Question 3

What happens to a plant cell in a solution with higher water potential?

Answer 3

The cell sap has a lower water potential than the solution. Water enters the cell via osmosis through the partially permeable cell membrane. The cell expands and becomes turgid. The vacuole increases in size and pushes the cytoplasm against the cell wall.

Question 4

What happens to an animal cell in a solution with higher water potential?

Answer 4

The cytoplasm has a lower water potential than the solution. Water enters the cell via osmosis through the partially permeable cell membrane. The cell expands in size and bursts.

Question 5

What happens to a plant cell in a solution with lower water potential?

Answer 5

The cell sap has a higher water potential than the solution. Water from the vacuole and cytoplasm leaves the cell through the partially permeable cell membrane. The cell decreases in size and becomes flaccid. The vacuole decreases in size as the cytoplasm shrinks away from the cell wall. The cell becomes plasmolysed.

Question 6

What happens to an animal cell in a solution with lower water potential?

Answer 6

The cytoplasm has a higher water potential than the solution. Water from the cytoplasm leaves the cell through the partially permeable cell membrane. The cell decreases in size and becomes crenated.

Question 7

What is active transport?

Answer 7

Active transport is the process in which energy is used to move particles of a substance across a membrane against its concentration gradient.