3. Movement into and out of cells

Question 1

Define

Diffusion

Answer 1

The net movement
of particles from a region of their higher
concentration to a region of their lower
concentration (down a concentration
gradient), as a result of their random movement

Question 2

Where does the energy for diffusion come from?

Answer 2

The kinetic energy of random movement of
molecules and ions

Question 3

Factors affecting diffusion?

Answer 3

• surface area increses, rate of diffusion increases
• temperature increases, rate of diffusion increases
• concentration gradient increase, rate of diffusin increases
• distance increases, rate of diffusion decreases

surface area to volume ratio

Question 4

Function of water in the body?

Answer 4

As a solvent in
organisms, in homeostasis

Question 5

Define

Osmosis

Answer 5

The net movement of
water molecules from a region of higher water
potential (dilute solution) to a region of lower
water potential (concentrated solution), through
a partially permeable membrane

Question 6

4-6 marks

Describe the importance of osmosis for plant support.

Answer 6

If the water potential is higher outside the plant, water moves into the cell, by osmosis. This causes the vacuole become Turgid to swell and push against the cell wall, to maintain the shape. This is Turgor Pressure
If the water potential is lower outside the plant, water is lost by the cells due to osmosis and the vacuole becomes Flaccid, and the cell can no longer maintain its shape. if this continues further, the cell membrane will separate from the cell wall and the cell is said to be Plasmolysed.

Question 7

Define

Active transport

Answer 7

The movement of
particles through a cell membrane from a region
of lower concentration to a region of higher
concentration (i.e. against a concentration
gradient), using energy from respiration.

Question 8

Examples of Active transport

Answer 8

Uptake of mineral ions by the root hair cells and protein carriers