A pondweed shoot is kept at 60 ∘C60\,^\circ\text{C}60∘C for several minutes. It is then returned to 20 ∘C20\,^\circ\text{C}20∘C, but its rate of photosynthesis remains much lower than before heating.
Which explanation best accounts for this result?
Some chloroplasts absorbed heat and now no longer require light energy.
Some chloroplasts released oxygen and now use oxygen instead of water.
Some enzymes moved faster and now catalyse all reactions more effectively.
Some enzymes changed shape and no longer catalyse reactions effectively.
44 exam-style questions on Edexcel GCSE Biology 6.1 Photosynthesis, covering 6.1.1 Photosynthetic organisms as producers, 6.1.2a Limiting factors on the rate of photosynthesis, 6.1.2b Interactions of limiting factors on photosynthesis, and 6.1.3 Inverse square law and light intensity. Each one has a worked solution and a mark scheme showing where the marks go.