4.1 The photosynthesis reaction
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Write the word equation for photosynthesis.
Mark scheme
- carbon dioxide + water (1)
- → glucose + oxygen (1)
- allow light / chlorophyll above the arrow
Model answer
carbon dioxide + water → glucose + oxygen
Where in a plant cell does photosynthesis take place?
Choose one answer.
Correct Not quite: the answer is Chloroplasts
Mark scheme
B: chloroplasts
Model answer
B: in the chloroplasts, which contain chlorophyll.
Photosynthesis is an endothermic reaction. Explain what this means.
Mark scheme
- energy is taken in / transferred from the surroundings (1)
- (as) light energy (absorbed by chlorophyll) (1)
Model answer
Energy is transferred from the environment to the chloroplasts, in the form of light.
Describe how a leaf obtains the carbon dioxide and the water it needs for photosynthesis.
Mark scheme
- carbon dioxide diffuses in through the stomata (1)
- water travels up from the roots in the xylem (1)
Model answer
Carbon dioxide diffuses into the leaf through the stomata. Water is absorbed by the roots and carried to the leaf in the xylem.
Complete the balanced symbol equation for photosynthesis.
6CO2 + 6H2O → ______ + ______
Mark scheme
- C6H12O6 (1)
- 6O2 (1)
Model answer
6CO2 + 6H2O → C6H12O6 + 6O2
Explain why plants and algae are important for nearly all life on Earth.
Mark scheme
- they are producers / make glucose / food (1)
- start of food chains / energy enters ecosystems through them / produce oxygen (1)
Model answer
They are producers: the glucose they make by photosynthesis is the start of food chains, and they release the oxygen other organisms need.
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