Unit 1.2 Transport across Cell Membranes

Question 1

What does the cell membrane consist of

Answer 1

• Phospholipids and proteins
• It is selectively permeable

Question 2

What is passive transport

Answer 2

• It is the movement of molecules down the concentration gradient and does not require energy

Question 3

What are two examples of passive transport

Answer 3

• Diffusion and osmosis

Question 4

What is a concentration gradient

Answer 4

• A concentration gradient is the difference in concentration between one place and another

Question 5

What is diffusion

Answer 5

• Diffusion is the movement of molecules down the concentration gradient from a high concentration to a low concentration
• This is a passive process so does not require energy

Question 6

What is osmosis

Answer 6

• Osmosis is the movement of water molecules down the concentration gradient from a high water concentration to a low water concentration across a selectively permeable membrane
• This is a passive process so does not require energy

Question 7

What is active transport

Answer 7

• Active transport is the movement of membrane proteins up the concentration gradient from a low concentration to a high concentration, against the concentration gradient
• This requires energy

Question 8

How does active transport get energy

Answer 8

• Active transport requires energy in the form of ATP so that membrane proteins can move molecules against the concentration gradient

Question 9

What happens to animal cells in lower water concentrations solution compared to its cytoplasm

Answer 9

• The animal cell will lose water by osmosis and shrink

Question 10

What happens to animal cells in a higher water concentration solution compared to it’s cytoplasm

Answer 10

• The animal cell will gain water by osmosis, swell up and burst

Question 11

What happens to a plant cell when you put it in a higher water concentration compared to its cytoplasm

Answer 11

• The plant cell will gain water through osmosis and become turgid
• A turgid plant cell has a full vacuole and the cytoplasm and the cell membrane push up against the wall

Question 12

What happens to a plant cell when you put it in a lower water concentration compared to its cytoplasm

Answer 12

• The plant cell will lose water through osmosis and become plasmolysed
• A plasmolysed plant cell has a small vacuole and cytoplasm and the cell membrane pulls away from the cell wall