UNIT 1 - Transport Across Membranes

Question 1

the cell membrane contains:

Answer 1

• phospholipid molecules (double layer)

* patchy mosaic of protein molecules

Question 2

how can substances move in or out of a cell?

Answer 2

• diffusion
• osmosis
• active transport

Question 3

name two types of passive transport.

Answer 3

diffusion and osmosis.

Question 4

describe passive transport.

Answer 4

passive transport is the movement of a substance down a concentration gradient. this does not require energy.

Question 5

why do cells use diffusion?

Answer 5

so they can move useful substance into the cell and waste products out.

Question 6

name useful substances needed by cells. (3)

Answer 6

• glucose
• oxygen
• amino acids

Question 7

name waste products removed from cells. (2)

Answer 7

• carbon dioxide

* urea

Question 8

describe osmosis.

Answer 8

the diffusion of water. does not require energy.

Question 9

what affects whether the cell loses or gains water?

Answer 9

the water concentration of the solution outside of the cell.

Question 10

osmotic effects on animal cells - normal red blood cell - pure water

Answer 10

water goes into cell, cell bursts.

Question 11

osmotic effects on animal cells - normal red blood cell - weak salt solution.

Answer 11

cells are the same, no movement, so no change.

Question 12

osmotic effects on animal cells - normal red blood cell - strong salt solution

Answer 12

water goes out of cell - so cell shrinks.

Question 13

osmotic effects on plant cells - normal plant cell - pure water.

Answer 13

water passes into cell, cell becomes turgid (filled).

Question 14

osmotic effects on plant cells - normal plant cell - weak sugar solution

Answer 14

concentration in and out cell are the same, no movement.

Question 15

osmotic effects on plant cells - normal plant cell - strong sugar solution.

Answer 15

water passes out of cell becomes plasmolysed.

Question 16

describe active transport.

Answer 16

the movement of molecules or ions from a lower to higher concentration against a concentration gradient. requires energy.