Part 1: Diffusion And Factors Affecting Diffusion

Question 1

State the definition of diffusion

Answer 1

The net movement of particles of a gas or solute from an area of higher concentration to an area of lower concentration down a concentration gradient

Question 2

Name 3 substances that diffuse into animal cells

Answer 2

1. Oxygen
2. Glucose
3. Fatty acids and glycerol

Question 3

Name 4 substances that diffuse out of cells

Answer 3

1. Carbon dioxide
2. Water
3. Amino acids
4. Urea

Question 4

An experiment takes place.
1. Collect two pieces of beetroot
2. Fill two boiling tubes with the same volume of water- one with cold water and the other with warm water
3. At exactly the same time, place knew beetroot piece into each boiling tube
4. Record your observations every minute either in the form of a table or a diagram
5. Continue for at least 5 minutes

(i) What can you conclude from this experiment?
(ii) Why might your results be subjective?
(iii) Evaluate the experiment design of the experiment

Answer 4

(i) The warmer the water, the faster the rate of diffusion
(ii) Because the experiment was performed only once, therefore the result achieved may be an outlier. Also, the way we view colours is subjective.
(iii) The ice kept the beetroot at the top of the boiling tube

Question 5

Name factors that will increase the rate of diffusion into the cell (7)

Answer 5

• Increased temperature
• Increased concentration gradient
• Decreased amount of substance inside cell
• Having lots of infolding of the cell membrane
• Adding more water inside the cell (i.e. diluting inside)
• Increase the amount of substance outside the cell
• Increased surface area

Question 6

Name the factors decreasing the rate of diffusion into the cell (6)

Answer 6

• Decreased temperature
• Decreased concentration gradient
• Decreased amount of substance outside the cell
• Increases amount of substance inside cell
• Adding more water outside the cell (i.e. diluting outside)
• Decreased surface area

Question 7

Define osmosis

Answer 7

A special case of diffusion, including water
Osmosis is the diffusion of water from an area of higher water potential (i.e., a dilute solution with higher water concentration) to an area lower water potential (i.e., a concentrated solution with a lower water concentration) through a partially permeable membrane