2. Movement in and out of cells

Question 1

What is diffusion?

Answer 1

Net movement of molecules from a region of higher concentration to a region of lower concentration.

Question 2

Diffusion in living organisms

Answer 2

1. CO2 diffuses from the air into the leaves, through the stomata.
2. O2 diffuses out of the leaf into the air after photosynthesis.
3. Gas exchange for respiration in animals and plants. Cell membranes are freely permeable to O2 and CO2

Question 3

What is osmosis?

Answer 3

Net movement of water molecules from a region of higher water potential to a region of lower water potential.

Question 4

Osmosis and animal cells

Answer 4

1. Hypertonic (concentrated)
   - Cytoplasm shrinks
   - The cell shrivels up
2. Hypotonic (dilute)
   - Stretches and swells
   - Eventually bursts
3. Isotonic

Question 5

Osmosis and plant cells

Answer 5

1. Plasmolysed
   - Vacuole and cytoplasm shrinks
   - Cell membrane tears away from the cell wall
2. Turgid
   - Cytoplasm and vacuole swell
   - Cell wall keeps it from bursting
   - Cytoplasm presses out against the cell wall. The cell wall resists and presses back
   - Keeps the plant to stay upright and leaves firm
3. Flaccid
   - Cytoplasm shrinks and does not push outwards
   - Plant loses firmness and began to wilt

Question 6

What is active transport?

Answer 6

Net movement of molecules from a region of lower concentration to a region of higher concentration.