Which is the equation for photosynthesis? Tick (✔) one box - AQA - GCSE Biology: Combined Science - Question 1 - 2021 - Paper 1

The independent variable in this investigation is:

Distance of the pondweed from the lamp.

An increase in temperature could speed up the rate of enzymatic reactions involved in photosynthesis, resulting in a higher production of bubbles of gas. However, if the temperature gets too high, it might denature the enzymes, ultimately reducing the rate of photosynthesis.

One way to improve the investigation is to use a heat shield between the lamp and the pondweed to prevent excess heat from affecting the water temperature.

1. Allow the pondweed time to equilibrate before taking measurements to ensure consistent gas production.
2. Use a controlled source of carbon dioxide, such as adding sodium bicarbonate to the water, to ensure that CO2 levels do not vary during the experiment.

When the pondweed was 40 cm from the lamp, 16 bubbles of gas were produced in 5 minutes.

Thus, the rate of photosynthesis is given by:

$Rate = \frac{16 \text{ bubbles}}{5 \text{ minutes}} = 3.2 \text{ bubbles per minute}$

As the distance of the pondweed from the lamp increases, the number of bubbles produced decreases. This suggests that light intensity is inversely related to distance.

The data from Table 1 should be plotted on Figure 2 with the distance on the x-axis and the number of bubbles on the y-axis. Ensure that all points are plotted correctly.

To draw a line of best fit, locate two points that represent the trend, ensuring the line passes through as many points as possible, demonstrating the overall relationship between distance and number of bubbles.

Based on the trend observed in Figure 2, it can be predicted that the number of bubbles produced when the pondweed is 60 cm from the lamp would be approximately 8 bubbles.