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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, due to more energy being available for the biochemical processes involved. However, this increase continues only until a certain point, where additional increases in light intensity will not raise the rate further. At this point, another factor, such as carbon dioxide or temperature, becomes limiting, causing the rate of photosynthesis to level off.
Step 2
Explain the effect of temperature on the rate of photosynthesis.
Answer
As temperature increases, the rate of photosynthesis initially rises because enzymes involved in photosynthesis become more active, facilitating more reactions. However, there is an optimal temperature above which enzyme activity begins to decline. If the temperature exceeds this optimum level, enzymes can become denatured, leading to a decrease in the rate of photosynthesis.
Step 3
Explain how substances are moved through a plant by transpiration and translocation.
Answer
Transpiration refers to the movement of water from the roots through the xylem, up to the leaves where it evaporates through small openings called stomata. This process is driven by evaporation and helps create a negative pressure that pulls water upwards through capillary action.
Translocation, on the other hand, involves the movement of dissolved sugars, primarily sucrose, from the leaves through the phloem to other parts of the plant where they are needed. This flow can be bidirectional, ensuring that all parts of the plant receive essential nutrients.