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9. (a) State a precise role for each of the following in photosynthesis: (i) Carbon dioxide (ii) Water (b) Answer the following questions in relation to an activity that you carried out to investigate the influence of light intensity OR carbon dioxide concentration on the rate of photosynthesis - Leaving Cert Biology - Question 9 - 2007
Question 9
9. (a) State a precise role for each of the following in photosynthesis: (i) Carbon dioxide (ii) Water (b) Answer the following questions in relation to an activi... show full transcript
Worked Solution & Example Answer:9. (a) State a precise role for each of the following in photosynthesis: (i) Carbon dioxide (ii) Water (b) Answer the following questions in relation to an activity that you carried out to investigate the influence of light intensity OR carbon dioxide concentration on the rate of photosynthesis - Leaving Cert Biology - Question 9 - 2007
Step 1
State a precise role for each of the following in photosynthesis: (i) Carbon dioxide
Answer
Carbon dioxide is essential in photosynthesis as it provides carbon, which is a crucial element for the formation of glucose during the Calvin cycle. It is absorbed by plants through the stomata and is transformed into organic compounds.
Step 2
State a precise role for each of the following in photosynthesis: (ii) Water
Answer
Water is vital for photosynthesis as it supplies electrons during the photolysis process. It contributes hydrogen ions (protons) that are used to form glucose and other carbohydrates, and it also helps in maintaining turgor pressure in plant cells.
Step 3
Step 4
Answer the following questions in relation to an activity that you carried out to investigate the influence of light intensity OR carbon dioxide concentration on the rate of photosynthesis. (ii) How did you vary light intensity OR carbon dioxide concentration?
Answer
I varied the light intensity by changing the distance of the lamp from the Elodea plant. For carbon dioxide concentration, I adjusted the quantity of sodium bicarbonate (NaHCO3) added to the water.
Step 5
Answer the following questions in relation to an activity that you carried out to investigate the influence of light intensity OR carbon dioxide concentration on the rate of photosynthesis. (iii) State a factor that you kept constant during the investigation.
Answer
The temperature of the water was kept constant throughout the investigation to ensure that it did not affect the rate of photosynthesis.
Step 6
Answer the following questions in relation to an activity that you carried out to investigate the influence of light intensity OR carbon dioxide concentration on the rate of photosynthesis. (iv) How did you ensure that the factor that you mentioned in (iii) remained constant?
Answer
I ensured that the temperature remained constant by using a water bath to regulate the temperature during the experiment.
Step 7
Answer the following questions in relation to an activity that you carried out to investigate the influence of light intensity OR carbon dioxide concentration on the rate of photosynthesis. (v) How did you measure the rate of photosynthesis?
Answer
The rate of photosynthesis was measured by counting the number of oxygen bubbles released by the Elodea plant over a set period of time. Alternatively, I could have used a data logger to record the oxygen levels in the water.
Step 8
Answer the following questions in relation to an activity that you carried out to investigate the influence of light intensity OR carbon dioxide concentration on the rate of photosynthesis. (vi) Using labelled axes, sketch a graph to show how the rate of photosynthesis varied with the factor mentioned in (ii) above.
Answer
In the graph, the vertical axis (y-axis) is labelled 'Rate of Photosynthesis (bubbles/min or mg O2/min)' and the horizontal axis (x-axis) is labelled 'Light Intensity (cm from lamp)'. As light intensity increases, the rate of photosynthesis typically increases, showing a positive correlation until a saturation point is reached.