Unit 1: Transport Across Cell Membranes Booklet LOs

Question 1

1: Describe the structure of the cell membrane

Answer 1

The cell membrane is made of two main parts: proteins and phospholipids. The phospholipids make the membrane fluid and able to move. The protein parts are found within the membrane and on each surface

Question 2

2: State what is meant by ‘selectively permeable’

Answer 2

Property of cell membrane which allows small soluble molecules to pass through but which prevents large insoluble molecules from crossing the membrane

Question 3

3: Describe how a concentration gradient is formed

Question 4

4: State what is meant by passive transport

Answer 4

The movement of any substance other than water from a region of higher concentration to lower concentration until evenly spaced. This does not require energy by the cell.

Question 5

5: Give examples of substances which move by passive transport

Answer 5

Cordial through water.
Dye in water.
Oxygen into the body.
Co2 out of the body

Question 6

6: Explain the importance of passive transport to cells

Answer 6

Substances required by a cell move into the cell from a higher concentration outside the cell to a lower concentration inside the cell.
Harmful substances leave the cell by diffusion from a higher concentration inside the cell to a lower concentration outside the cell.

Question 7

7: State what is meant by osmosis in terms of water concentration

Answer 7

Osmosis is the movement of water from an area of higher water concentration to a lower water concentration across a selectively permeable membrane.

Question 8

8: Explain the osmosis effects of water on animal cells

Answer 8

When animal cells are placed in a solution with a higher water concentration, the water moves in by osmosis and the cells burst. When animal cells are placed in a solution with a lower water concentration, the water moves out by osmosis and the cells shrink. The animal cells burst because they don’t have a cell wall.

Question 9

9: Explain the osmosis effects of water of plant cells

Answer 9

When plant cells are placed in a solution with a higher concentration, the water moves in by osmosis and the cells become turgid. The cells do not burst because they have a cell wall. When plant cells are placed in a solution with a lower water concentration, the water moves out by osmosis and the cells become plasmolysed.

Question 10

10: State what is meant by active transport

Answer 10

The movement of a substance across a cell membrane from a lower to a higher concentration. This requires use of energy by the cell

Question 11

11: Describe the process of active transport

Answer 11

Active transport is when a substance moves across a cell membrane against a concentration gradient from a lower concentration to a higher concentration. This process requires energy to transport the substance from a lower concentration to a higher concentration. Substances cross the membrane through a protein.

Question 12

12: Give examples of substances which move by active transport

Answer 12

Sodium and potassium

Question 13

13: State what factors limit the rate of active transport

Answer 13

Oxygen concentration
Glucose concentration
Temperature