Photosynthesis Practice Questions

Complete the word equation for photosynthesis.

$\text{.....................} + \text{water} \xrightarrow{\ \text{light}\ } \text{glucose} + \text{.....................}$

Which substance in a seaweed cell is the green pigment that absorbs light energy?

• A cellulose
• B chlorophyll
• C chromosome
• D cytoplasm

Explain why photosynthesis is described as an endothermic reaction.

Name the producer in this food chain.

Explain why photosynthetic organisms such as algae are described as the main source of biomass in a food chain.

Name the gas that is released in the bubbles.

Calculate the rate of photosynthesis, in bubbles per minute, when the pondweed was 20 cm from the lamp.

After 40 minutes, the indicator in the tube closest to the lamp had turned purple. Explain this result.

Give two variables the student should have controlled in this investigation.

Give one safety precaution the student should take when carrying out this investigation.

State the temperature, from these results, at which the rate of photosynthesis was highest.

Explain the effect of temperature on the rate of photosynthesis shown by these results.

At very low light intensities all three curves are the same. Name the factor that is limiting the rate of photosynthesis at these low light intensities.

Explain why curve A levels off at a higher rate of photosynthesis than curve B.

Explain why curve C levels off at a lower rate of photosynthesis than curve B.

Calculate the relative light intensity when the lamp was 0.25 m from the pondweed.

The student moved the lamp from 0.10 m to 0.20 m from the pondweed. Explain why this caused such a large decrease in the rate of photosynthesis.

Identify the anomalous result and suggest a reason for it.

Explain why counting bubbles is not an accurate way of measuring the rate of photosynthesis, and describe how the measurement could be improved.

Explain one other way the student could improve this investigation so that the conclusion about light intensity is more valid.

A grower produces tomato plants in a greenhouse in the UK. In winter the greenhouse is cold and the days are short, and the grower's tomato plants grow slowly.

The grower can install lamps, heaters and a carbon dioxide generator.

Explain how changing light intensity, temperature and carbon dioxide concentration inside the greenhouse would affect the rate of photosynthesis of the tomato plants, and why changing only one of these factors may not increase the rate.