4.4 Uses of glucose from photosynthesis
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Give three ways a plant uses the glucose made by photosynthesis.
Mark scheme
Any three from:
- respiration (1)
- converted to starch for storage (1)
- to make fats / oils for storage (1)
- to make cellulose (for cell walls) (1)
- to make amino acids / proteins (1)
Model answer
For respiration, to make cellulose for cell walls, and stored as starch.
Explain why plants store carbohydrate as starch rather than as glucose.
Mark scheme
- starch is insoluble (1)
- so it does not affect water movement / osmosis (1)
Model answer
Starch is insoluble, so storing it does not cause water to move into the cells by osmosis, as glucose would.
What must be combined with glucose to make amino acids, and where does the plant get it from?
Mark scheme
- nitrate ions (1)
- from the soil (by active transport into root hairs) (1)
Model answer
Nitrate ions, which are absorbed from the soil by the roots.
Which substance made from glucose strengthens plant cell walls?
Choose one answer.
Correct Not quite: the answer is Cellulose
Mark scheme
C: cellulose
Model answer
C: cellulose.
A leaf kept in the dark for two days gives a negative result with the iodine test. Explain why.
Mark scheme
- no light so no photosynthesis / no glucose made (1)
- stored starch used up (in respiration) (1)
Model answer
In the dark there is no photosynthesis, so no new glucose is made, and the starch already stored is broken down and used in respiration.
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