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(a) What is diffusion?
(b) How do the following factors affect the rate of diffusion?
(i) Diffusion gradient
(ii) Surface area to volume ratio.
(iii) Temperature
(c) Outline three roles of active transport?

Answer Text:
a)- Is the movement of molecules from a region of high concentration to a region of low concentration.
b)i)- The higher the diffusion gradient (difference in concentration between two points/regions) the higher the rate of diffusion while the lower the diffusion gradient the lower the rate of diffusion.
ii)- The higher the surface area to volume ratio, the faster the rate of diffusion while the lower ratio the slower the rate of diffusion.
iii)- Increasing in temperature increases energy content in a molecule hence faster rate of diffusion.
c)- Reabsorption of glucose, amino acids, salts in the kidney tubules back into the blood circulation.
- Absorption digested food from the alimentary canal.
- Excretion of waste products of metabolism
from body cells into the blood.