OCR Gateway GCSE Biology

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GCSEBiologyOCR GatewayTopic Questions1. Cell Level Systems1.4 Photosynthesis

1.4 Photosynthesis

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1a
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Two students investigate photosynthesis. Look at the notes from their investigation.

  Aim of the experiment

  To use pondweed to see how light intensity affects the rate of photosynthesis.

  Method

  1. Set up the apparatus as in the diagram.
  2. Leave the pondweed for five minutes so it can adjust to the new light intensity.
  3. Count the number of bubbles given off by the pondweed in one minute.
  4.  Move the lamp 10cm further away from the beaker.
  5. Leave the pondweed for five minutes so it can adjust again.
  6. Count the number of bubbles given off by the pondweed in one minute.
  7. Repeat by moving the lamp further away from the beaker by 10cm intervals until 50cm is reached.
      

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What is the independent variable in their investigation?

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1b
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(i)
Explain why counting the number of bubbles will not give an accurate measure of the rate of photosynthesis.

[2]

(ii)
Describe how the students could develop their investigation to improve the accuracy of their results.

[2]

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1c
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The table shows the results.

Distance from lamp to beaker
(cm)

 Number of bubbles given off
(per minute)
10 30
20 14
30 6
40 2
50 0

(i)

One student started to draw a graph but did not finish.

Complete the graph using the results in the table and draw a curve of best fit.
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[4]
(ii)
Write down what the students could conclude from their investigation.

Include data from the results table in your answer.
[2]

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2a
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Photosynthesis involves reactions that are endothermic.

What is meant by the term endothermic reaction?

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2b
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The graph is from an experiment to show the effect of temperature on the rate of photosynthesis.
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Draw a line of best fit.

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2c
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Higher Tier only

Look at the graph. It shows how light intensity affects the rate of photosynthesis.

The lines show different carbon dioxide concentrations and temperatures.

q21c-paper1h-june2018-ocrgcsebio

Explain what is limiting the rate of photosynthesis at the three points A, B and C on the graph.

Use evidence from the graph in your answer.

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3a
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Photosynthesis takes place inside chloroplasts.

(i)
Complete the chemical equation for photosynthesis.

6CO2 + .......................... → C6H12O6 + ........................
[2]
(ii)
Energy is taken in from the surroundings for photosynthesis to take place.

What name is used to describe reactions that take in energy?
[1]

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3b
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The graph is from an experiment to show the effect of temperature on the rate of photosynthesis.
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(i)
What is the optimum temperature for photosynthesis in this experiment?
[1]
(ii)
The rate of photosynthesis was recorded in 5°C intervals.

The experiment could be improved to get a more precise value for the optimum temperature.

Explain how.
[2]

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4
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The student thinks that shade from the tree is affecting the plants.

Explain how the student’s results show this.

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