1. Why would enzymes have different optimums

2. Plenary Write a conclusion for the following results
Temp (oC)
Gas produced (cm3) 10 5 20 17 30 23 40 55 50 45
Write a conclusion for the following results
What is the trend?
What science explains the trend

3. Starter Organise these sentences to give a definition for diffusion.
(Use page 9 of the book to help if needed)
from an area of higher concentration
Net movement of particles
until equilibrium is reached
to an area of lower concentration

4. Why do we need diffusion?
What process occurs in all cells and is essential to life?
Respiration (aerobic)
A B C
What substances need to enter the cell for respiration to occur?
Oxygen and food (glucose)
What products of respiration need to leave the cell?
Carbon dioxide and (excess) water
Oxygen, carbon dioxide and glucose move by diffusion, they diffuse across the .

5. Examples of where diffusion is important
Between air in alveoli to blood
(oxygen and carbon dioxide)
From the small intestine into the blood
(digested food)
From the mothers blood into an unborn childs across the placenta
What factors affect the rate of diffusion?
How can we make it faster/slower?

6. So how can we make diffusion faster?
Fick’s law
All organisms need to exchange substances such as food, waste, gases and heat with their surroundings.
These substances must diffuse between the organism and the surroundings.
The rate at which a substance can diffuse is given by Fick's law:
Rate of diffusion = surface area x concentration difference
Distance
So how can we make diffusion faster?

7. Increase surface area of the tissue
Increase the concentration gradient (bigger difference between the concentrations)
Decrease the distance it has to travel through (less cells)
We need to look at how particular substances manage to do this
Alveoli
Small intestine
Placenta

8. Way(s) that this is achieved
Increasing diffusion rate in the lungs Use pages to complete the table
Way(s) that this is achieved
Large surface area
Shape of the alveoli – folded surface
Maintenance of steep concentration gradient
Constant replacement of air in lungs to keep oxygen concentration high
Constant removal of oxygenated blood and delivery of deoxygenated blood
Short diffusion pathway
Alveolus and capillary are only one cell thick (few membranes to cross)
Thin cells

9. What other adaptations do the alveoli have?
Moist – maintains permeability
Permeability of cells – allow gases through easily

10. Way(s) that this is achieved
Increasing diffusion rate in the small intestine Use pages to complete the table
Way(s) that this is achieved
Large surface area
Villi and microvilli
Maintenance of steep concentration gradient
Constant removal of nutrient rich blood and delivery of nutrient deficient blood
Short diffusion pathway
Blood vessels protrude up the villi
Villi have one cell between the intestine and the blood vessels collecting food

11. Way(s) that this is achieved
Increasing diffusion rate at the placenta Use pages to complete the table
Way(s) that this is achieved
Large surface area
Many folds
Maintenance of steep concentration gradient
Constant replacement of mother and foetal bloods
Short diffusion pathway
Mothers blood and foetus blood come very close together without mixing, they are separated by thin walls of tissue

12. Plenary Complete the sheet from what you have done today in the lesson
Glue in
Hand in your books for marking