Unit 1.2

Question 1

What does the cell membrane consist of

Answer 1

Phospholipids and proteins and is selectively permeable

Question 2

What does selectively permeable mean

Answer 2

The membrane only allows certain types of molecules to pass through it

Question 3

Define passive transport

Answer 3

Down the concentration gradient and does not require energy

Question 4

What are two examples of passive transport

Answer 4

1. Diffusion
2. Osmosis

Question 5

Define diffusion

Answer 5

Diffusion is the movement of molecules down a concentration gradient from a higher to a lower concentration

Question 6

Define osmosis

Answer 6

The movement of water molecules from a higher water concentration to a lower water concentration through a selectively permeable membrane

Question 7

What happens to animal cells in low water concentrations and explain why

Answer 7

The cell will lose water by osmosis and shrink
This is because water moves from a high water concentration inside the cell to a low water concentration outside the cell through osmosis

Question 8

What happens to animal cells in high water concentrations

Answer 8

The cell will gain water by osmosis and swell up and burst
This is because water moves from a high water concentration outside the cell to a low water concentration inside the cell through osmosis it bursts because it does not have a cell wall to give it more structure

Question 9

What happens to plant cells in high water concentrations

Answer 9

The cell becomes turgid (enlarged and swollen with water)
Water will move from a high water concentration outside the cell to a low water concentration inside the cell through osmosis. The presence of the plant cell wall prevents plant cells from bursting

Question 10

What happens to plant cells in low water concentration

Answer 10

The cell will become plasmolysed (vacuole has shrunk and the membrane has pulled away from the wall due to water loss)
Water moves from a high water concentration inside the cell to a low water concentration outside of the cell through osmosis. The cell becomes plasmolysed because the vacuole has shrunk and the cell membrane has pulled away from the wall

Question 11

Define active transport

Answer 11

Active transport is the movement of molecule from a low concentration to a high concentration against the concentration gradient

Question 12

What does active transport require

Answer 12

Active transport requires energy for membrane proteins to move molecules and ions against the concentration gradient