Mr Harrison diffusion and osmosis

1. Diffusion, osmosis and active
transport
LO: To learn how substances get into and out of cells.
Thinking question:
How are oxygen and carbon dioxide transported in your
body?
Oxygen is transported by the red blood cells and carbon
dioxide is transported in your blood plasma.

2. Learning outcomes
• Describe the meaning of the term diffusion, osmosis
and active transport.
• Explain examples of where diffusion and osmosis
occur in the human body
• Suggest reasons why active transport is different to
diffusion and osmosis.
• Stretch: Create model answers to past exam style
questions.

3. Diffusion
• This is a process that is vital to all living organisms.
• Diffusion is when molecules move from an area of
high concentration to a lower concentration until
equalibrium is reached.
• We say the molecules diffuse along a concentration
gradient.

4. Diffusion

5. Diffusion example

6. Diffusion in your body
• Task: On your paper, write down how oxygen moves
from the lungs into the cells in the body that need it
(e.g. brain cells).
• Thinking prompts:
• Where does it enter your body?
• Where will the concentration of oxygen be highest?
• Keywords: oxygen, concentration, red blood cells,
diffuse, high, low, brain cells.

7. Your idea time
On your paper write down
what you think the term
active transport means.

8. Active transport
• Active transport is when cells move molecules in the
opposite direction, against the concentration
gradient.
• This process requires energy.
• If you are asked for an example in your exam, glucose
is absorbed from the small intestine into the blood by
active transport.

9. Learning check
• Have a go at the two learning check questions to make
sure you understand diffusion and active transport.
• What is diffusion?
• Diffusion is when molecules move from an area of
high concentration to a lower concentration until
equalibrium is reached.
• What is active transport?
• Active transport is when cells move molecules in the
opposite direction, against the concentration
gradient.

10. Osmosis
• Osmosis is when water diffuses through a partially
permeable membrane so that the concentration on
each side becomes more equal.
• So, the movement of water is from a dilute to more
concentrated solution.

11. Lets look at it in detail
A

12. What happens next?
• A chip is placed into the following beakers. What will
happen to the size of the potato chip? Explain your
answer.

15. Gill and Jon

16. What have you learned today?
• Describe the meaning of the term diffusion, osmosis
and active transport.
• Explain examples of where diffusion and osmosis
occur in the human body
• Suggest reasons why active transport is different to
diffusion and osmosis.
• Stretch: Create model answers to past exam style
questions.

17. Extension
• The cells in your body are surrounded by a liquid
called tissue fluid, which contains dissolved
substances.
• If the tissue fluid is more dilute than the fluid inside
the cells, what will happen?