A technician places six barley seedlings in a controlled chamber under bright light. An automatic system keeps the carbon dioxide concentration constant by replacing the gas as the seedlings absorb it. The volume of carbon dioxide replaced each hour is used to estimate the rate of photosynthesis.
The same seedlings are used throughout. The temperature settings are tested from lowest to highest.
| Temperature in ∘C^\circ\text{C}∘C | Carbon dioxide uptake in cm3 h−1\text{cm}^3\ \text{h}^{-1}cm3 h−1 |
|---|---|
| 12 | 1.8 |
| 20 | 4.6 |
| 28 | 7.5 |
| 36 | 3.9 |
| 44 | 0.5 |
Give the temperature setting at which the greatest carbon dioxide uptake was recorded.
From 12 ∘C12\ ^\circ\text{C}12 ∘C to 28 ∘C28\ ^\circ\text{C}28 ∘C, the carbon dioxide uptake becomes faster. Explain this change in terms of the particles involved in enzyme-controlled reactions.
Calculate the percentage change in carbon dioxide uptake when the chamber temperature is raised from 20 ∘C20\ ^\circ\text{C}20 ∘C to 36 ∘C36\ ^\circ\text{C}36 ∘C.
The technician tested the seedlings at 44 ∘C44\ ^\circ\text{C}44 ∘C only after completing all the other measurements. Suggest a reason for choosing this order.
117 exam-style questions on OCR GCSE Biology 1.4 Photosynthesis, covering 1.4.1 Photosynthesisers as biomass producers, 1.4.2 Factors affecting the rate of photosynthesis, and 1.4.3 Limiting factors in photosynthesis. Each one has a worked solution and a mark scheme showing where the marks go.