Photosynthesis (Edexcel GCSE Biology)

Figure 1 shows a food chain. 

Figure 1

(i) Give the name of the trophic level of the small plants. 

(1)

(ii) The arrows in a food chain represent the flow of energy from one trophic level to the next. 

Describe how the plants gain the energy that they can then pass onto the aphids. 

(2)

(iii) The energy from this process is converted into biomass in the plant.
The small plants contain 17.5 g per m² of biomass and they transfer 20% of this to the aphids.

Calculate the biomass of the aphids in g per m².

(2)

Figure 2 show the rate of photosynthesis in a field containing small plants, during a 12 hour period. 

Figure 2

(i) Describe the trend shown in Figure 2 from 6 am to 6pm. 

(2)

(ii) Suggest two factors that may affect the rate of photosynthesis during this 12 hour period. 

(2)

Higher Tier only

A scientist investigated the effect of light intensity on the rate of photosynthesis of the aquatic Cabomba plant. 

A lamp was used as a source of light. The lamp was placed at different distances (d) from the Cabomba plant, and the number of bubbles produced in 60 seconds was used to calculate the rate of photosynthesis. 

The light intensity was then calculated using the inverse square law .

Figure 1 shows the scientist's results. 

Figure 1

(i) Calculate the light intensity when the lamp is 20 cm from the Cabomba plant.

(2)

(ii) Use the information from Figure 1 to describe the effect of light intensity on the rate of photosynthesis. 

(2)

(iii) The scientist counted the number of bubbles produced by the Cabomba plant.

Explain how you could improve the method to measure the volume of gas released more accurately. 

(2)

Higher Tier Only

The student repeats the experiment, changing the lightbulb to allow for a higher light intensity to be achieved. The student found that despite the higher light intensity that the rate of reaction did not increase any further.

Explain why the rate of photosynthesis did not increase when the light intensity increased. 

Figure 1 shows a cross section through a leaf. 

Figure 1

Describe the process that takes place in a leaf to produce oxygen. 

Using Figure 2, state the location where most oxygen is produced, and describe the method by which oxygen leaves the leaf. 

Some of the oxygen does not leave the leaf and instead is used for another reaction within the leaf. 

(i) State the name of this reaction. 

(1)

(ii) At what time of day is more oxygen taken into the leaf than removed?

Explain your answer. 

(2)

The concentration of carbon dioxide in two areas of a rainforest was measured. Each measurement was taken three times. The results are shown in Figure 1.

Area A was full of large trees and area B was an area with a small number of small trees, as it was just recovering from some recent deforestation. 

Figure 1

(i) Calculate the mean carbon dioxide concentration in area B. 

(2)

(ii) Explain why all the carbon dioxide concentration readings for area B are higher than for area A. 

(2)

Higher Tier Only

The experiment was repeated in a high altitude area.

Suggest how the results would vary in the high altitude area compared to the data in Figure 2, and explain how this would affect the biomass of the trees in this area. 

A student placed some balls made of algae into each of four small glass bottles containing hydrogencarbonate indicator. 

Three of the bottles were sealed with a lid and placed at different distances from a light source. 

The fourth bottle was wrapped in opaque foil in order for the algae to be kept in the dark.

Hydrogencarbonate indicator changes colour due to the amount of carbon dioxide in the solution. 

The investigation was left for 50 minutes and the colour of hydrogencarbonate solution was recorded. 

Figure 1 shows this investigation.

Figure 1

(i) State two variables the student will need to control in this investigation. 

(2)

(ii) State the purpose of the bottle wrapped in foil in this investigation.

(2)

At the start of the investigation the hydrogencarbonate indicator was red in colour.

Figure 2 shows the colour of the hydrogencarbonate indicator in the four bottles at the end of the investigation. 

Figure 2

Explain why the hydrogencarbonate indicator in the bottle nearest to the light source turned purple. 

Figure 1 shows the effect of temperature on the rate of photosynthesis. 

Figure 1

Describe and explain the effect of temperature on the rate of photosynthesis

Figure 1 shows a cross section through a leaf.

Figure 1

(i) What is the name of the part labelled R in Figure 1?

(1)

(ii) Figure 2 shows the mass of glucose produced in each layer of a leaf per hour.

Figure 2

Describe the difference in the mass of glucose produced per hour in the palisade mesophyll and the mass of glucose produced in the spongy mesophyll shown in Figure 2.

(2)

Figure 3 shows how light intensity changed during one day.

Figure 3

Use the information in Figure 3 to explain why oxygen moved out of the leaf between 9 am and midday.

(i) Glucose is produced in a leaf.

Glucose is a

(1)

(ii) Describe a test for glucose.

(2)

Figure 4 shows an enzyme and three substrates found in plant cells.

Figure 4

The enzyme will only break down one of these substrates.

State the name of this enzyme.

Higher Tier Only

Figure 1 shows the effect of light intensity and temperature on the rate of photosynthesis.

Figure 1

(i) Describe the effect of light intensity on the rate of photosynthesis.

(2)

(ii) Explain the effect of temperature on the rate of photosynthesis.

(2)

Higher Tier Only

A student measured the rate of photosynthesis using algal balls in a laboratory.

The tube of algal balls was kept at a temperature of 25 °C and was moved to different distances from a light source.

The results of this investigation showed that the rate of photosynthesis is

Explain how substances are moved through a plant by transpiration and translocation.

Figure 1 shows an area of woodland with some small plants growing in the ground between the trees.

Colin Smith, CC BY-SA 2.0 <https://creativecommons.org/licenses/by-sa/2.0>, via Wikimedia Commons

Figure 1

The leaves of the small plants are green.

Describe how these plants make glucose.

Name a group of organisms that break down the dead leaves and release mineral ions into the soil.

The mineral ions are absorbed from the soil into the roots of plants.

Describe how these mineral ions are transported from the roots to the leaves of the plants.

A scientist recorded the mean light intensity and the mean number of small plants per m² for six 25m² areas of the woodland.

Figure 2 shows the results.

Figure 2

(i) Explain the effect of light intensity on the number of small plants per m²

(2)

(ii) State one variable the scientist should have controlled to make sure the light intensity measurements could be compared.

(1)

The scientist selects an area near the edge of the woodland where many stinging nettles are growing.

This area is partly shaded by the trees.

Describe how the scientist should use a belt transect to investigate how light intensity affects the growth of stinging nettles.

An investigation was carried out to test the effect of temperature on the rate of photosynthesis of pondweed.

The volume of oxygen produced per hour was measured. The results can be seen in Table 1.

Table 1

Calculate the mean rate of photosynthesis per hour when the temperature was 45 °C.

Plot the results from Table 1 onto an appropriate graph using the graph paper in Fig. 1.

Fig. 1

Describe and explain the results shown in the graph.

A farmer growing strawberries in his greenhouse used the results in Table 1 to decide on the best temperature for his greenhouse. He decided to heat the greenhouse to 30 °C.

When the farmer measured the rate of photosynthesis of his plants, he found the rate to be 11.5% slower than the data suggested.

Calculate the rate of photosynthesis that the farmer actually achieved at 30 °C.

Suggest why the farmer may not have achieved a rate of photosynthesis as high as the data in Fig. 1 predicted.

Figure. 1 shows the effect of several different factors on the growth of strawberry plants in a greenhouse.

Figure. 1

Describe and explain how temperature and light intensity affected the rate of photosynthesis up until 20°C.

Identify the limiting factor(s) between point X and Y in Fig. 1.

Calculate the percentage difference in the rate of photosynthesis at 25°C in the plants grown at low and high light intensity. Show your working and give your answer to one decimal place.

Higher Tier Only

Explain why light intensity is no longer limiting the rate of photosynthesis at temperatures higher than 30°C.

A student carried out an investigation into the effect of soil magnesium on plant growth. Magnesium is a key vitamin required in the synthesis of chlorophyll.

In this investigation, the student set up two different environments as follows:

1. One plant was grown in sterile soil, provided with distilled water and placed in bright light.

2. One plant was grown in sterile soil, provided with magnesium dissolved in distilled water and placed in bright light.

Predict what the student will have observed after two weeks of growing in these conditions.

Explain your prediction from part (a).

When selecting the plants for the investigation in part (a), the student made sure that they picked plants with the same number of leaves.

Explain why this was necessary.

One method that can be used to show that photosynthesis has occurred is to test the leaves with iodine.

Explain how this shows that photosynthesis has occurred.

Figure 1 shows the changes in carbon dioxide uptake and release over a 24 hour period in a tomato plant.

Figure 1

Explain what the graph shows at 7:30 and 19:30.

Calculate the percentage decrease in carbon dioxide uptake between 15:00 and 18:00 in Figure 1.

Higher Tier Only

With reference to the amount of carbon dioxide released and taken in, Figure 1 can be used to indicate how the rate of photosynthesis changes throughout the 24 hour period, assuming that the rate of respiration is constant during this time.

Explain how interactions between temperature and light intensity contribute towards the changes in photosynthesis represented in Figure 1.

Over 24 hours, the tomato plant takes in more carbon dioxide than it releases.

Explain the value of this to the tomato plant.