Differentiate between the following pairs on the basis of what is mentioned in brackets:
Active Transport and Diffusion [significance in plants]
Topic: Active transport and diffusion
Answer
ACTIVE TRANSPORT: mineral ions such as nitrates, sulphates, potassium and zinc are absorbed by the ROOTS from the soil AGAINST the concentration gradient, using energy supplied as ATP.
DIFFUSION: carbon dioxide needed for photosynthesis enters the LEAF through the stomata down its concentration gradient, requiring no energy.
The brackets ask for the SIGNIFICANCE IN PLANTS, so give a plant EXAMPLE of each rather than a general definition — that is what earns the mark.
WHY PLANTS NEED ACTIVE TRANSPORT: soil often contains a LOWER concentration of a mineral than the root cell already holds. Diffusion would move the mineral OUT of the root, not in. Active transport is the only way to go on absorbing it — and it is why root cells are rich in MITOCHONDRIA, which supply the ATP.
Note that WATER enters the root by OSMOSIS, a third process again — passive, but concerning the solvent and requiring a selectively permeable membrane.
| Point of difference | Active transport | Diffusion |
|---|---|---|
| Significance in plants | Absorption of mineral ions by the roots | Entry of carbon dioxide into the leaf for photosynthesis |
| Direction | Against the concentration gradient | Down the concentration gradient |
| Energy | Required (ATP) | Not required |