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Figure 9 shows the effect of light intensity and temperature on the rate of photosynthesis - Edexcel - GCSE Biology Combined Science - Question 5 - 2018 - Paper 1
Question 5
Figure 9 shows the effect of light intensity and temperature on the rate of photosynthesis. (i) Describe the effect of light intensity on the rate of photosynthesis.... show full transcript
Worked Solution & Example Answer:Figure 9 shows the effect of light intensity and temperature on the rate of photosynthesis - Edexcel - GCSE Biology Combined Science - Question 5 - 2018 - Paper 1
Step 1
Describe the effect of light intensity on the rate of photosynthesis.
Answer
As light intensity increases, the rate of photosynthesis also increases, indicating that light intensity is directly proportional to the rate of photosynthesis. However, this relationship only holds to a certain point, where it levels off. This plateau suggests that another factor, likely a limiting factor such as carbon dioxide or temperature, is affecting the rate of photosynthesis beyond that point.
Step 2
Explain the effect of temperature on the rate of photosynthesis.
Answer
The rate of photosynthesis generally increases with temperature up to an optimum point. As temperature increases, enzymes involved in photosynthesis catalyze more reactions, leading to a higher rate of photosynthesis. However, if the temperature continues to rise beyond the optimum, enzymes may become denatured, causing the rate of photosynthesis to decrease.
Step 3
Step 4
Explain how substances are moved through a plant by transpiration and translocation.
Answer
Transpiration involves the movement of water from the roots through the plant via the xylem, driven predominantly by evaporation from the leaves through the stomata. Water moves in one direction, assisted by capillary action and the cohesion-tension theory.
Translocation refers to the movement of sugars, primarily from the leaves through the phloem, where the flow is bidirectional. Sugars are transported as sucrose, and this process ensures that areas of the plant that need energy receive the necessary nutrients.