Key Area 1.2 - Transport Across Cell Membranes

Question 1

What are protein molecules

Answer 1

Channel
Anchored protein
Integral protein

The cell membrane controls the speed that substances pass through
Large molecules such as glucose require transport proteins to pass through

Question 2

What do the transport proteins determine

Answer 2

The transport proteins in a cell membrane determine which substances the membrane is permeable to

Question 3

What is diffusion

Answer 3

The passive movement of molecules from an area of high concentration to an area of low concentration across a selectively permeable membrane
Diffusion stops when the concentration of a substance is equal in both areas (no overall net movement)

Question 4

Why is diffusion important

Answer 4

Diffusion is important to cells because it allows them to gain useful substances they require to obtain energy and to grow. It also lets them get rid of waste products

Question 5

What is osmosis

Answer 5

The passive movement of water molecules from an area of high water concentration to an area of low water concentration across a selectively permeable membrane

Question 6

What happens to animal cells in a hypotonic solution

Answer 6

RBCs placed in a solution with a higher water concentration on the outside will gain water, swell up and burst
This is irreversible

Question 7

What happens to animals cells in a hypertonic solution

Answer 7

RBCs placed in a solution with a lower water concentration on the outside will lose water and shrink
This is reversible

Question 8

What happens to plant cells in a hypotonic solution

Answer 8

Plant cells placed in a solution with a higher water concentration on the outside will gain water and their cytoplasm and membrane pushing against the cell wall.
Turgid

Question 9

What happens to plant cells in a hypertonic solution

Answer 9

Plant cells placed in a solution with a lower water concentration on the outside will lose water and their cell membranes will pull away from the cell wall
Plasmolysed

Question 10

What is an isotonic solution

Answer 10

There is an equal concentration of water inside and outside the cell.
No overall net movement

Question 11

What is active transport

Answer 11

Then movement of molecules from an area of low concentration to an area of high concentration against a concentration gradient across a selectively permeable membrane
Sodium potassium pump

Question 12

What are lipid molecules

Answer 12

Lipid molecules are able to move around within the layers and give the cell membrane flexibility

Lipid inner (hydrophobic)
phosphohead (hydrophilic)
Water moves through quickly

Small molecules such as water, oxygen and carbon dioxide can pass through the lipids