Equal masses of sea lettuce are placed in seawater at 8 ∘C8\,^\circ\text{C}8∘C and 18 ∘C18\,^\circ\text{C}18∘C. Both temperatures are below the optimum for the enzymes involved.
The light intensity and carbon dioxide concentration are the same in both conditions. The sea lettuce at 18 ∘C18\,^\circ\text{C}18∘C releases oxygen more quickly.
Which explanation accounts for this difference?
Enzymes are denatured at 8 ∘C8\,^\circ\text{C}8∘C, so their active sites no longer fit the substrates and fewer complexes form.
Photosynthesis releases more energy at 18 ∘C18\,^\circ\text{C}18∘C, so the reactions of photosynthesis can proceed faster.
Chlorophyll absorbs more light energy at 18 ∘C18\,^\circ\text{C}18∘C, so more energy is transferred to make glucose.
Particles have more kinetic energy at 18 ∘C18\,^\circ\text{C}18∘C, increasing the frequency of successful collisions involving enzymes.
87 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.