Photosynthesis

Plants produce glucose by photosynthesis.

Complete the word equation for photosynthesis shown in Figure 2.

Figure 2

State why photosynthesis does not occur in the roots of plants.

Which is transported in the phloem?

Chlorophyll is found in green leaf cells.

Describe the role of chlorophyll in leaf cells.

A greenhouse contained an oil burning heater.

State two ways this could increase the rate of photosynthesis in the greenhouse.

Figure 3 shows part of the nitrogen cycle.

Use words from the box to complete the following sentences about the nitrogen cycle.

The nitrogen compounds in plants include_........

The nitrates from rotting dead plants are released into the soil by_........

180 million tonnes of nitrates were used by crops growing on farms in the UK in 2020.

Figure 4 shows the different sources of nitrates used by the crops.

Calculate the mass of nitrates from human-made fertiliser that was used by crops in 2020.

Some of the nitrates spread on fields as fertiliser get into lakes.

Name the type of pollution caused by the build-up of nitrates in lakes.

A student investigated how the concentration of nitrate affected the types of algae growing in three lakes.

Figure 5 shows microscope images of the algae in 1 mm³ of water, and the concentrations of nitrate ions in each lake.

Figure 6 shows a bar chart for the algae in lakes X, Y and Z.

Complete the bar chart for algae L and algae M in lake Z.

State two conclusions about the relationship between nitrate concentration and the algae in these lakes.

A build-up of algae on the surface of the lake can affect plants growing at the bottom of the lake.

Which statement shows how this would affect the plants at the bottom of the lake?

Figure 8 shows the lower epidermis of a leaf, with a stoma labelled.

(Source: © Quagga Media/Alamy Stock Photo)

Figure 8

State the number of guard cells shown in Figure 8.

State one gas that leaves the stomata and one gas that enters the stomata during daylight.

gas leaving stomata

gas entering stomata

State why the stomata close.

A student wanted to view the cross-section of a leaf on a prepared slide.

Describe how a light microscope would be used to observe this slide.

Sugars are transported from the leaves to the rest of the plant.

Explain how sugars are moved through the plant.

Plants need light for photosynthesis.

Part of the photosynthesis equation is shown below.

reactant A + water glucose + product B

Which row in the table shows reactant A and product B?

Name the green chemical in chloroplasts that absorbs light.

Plan an experiment to investigate if plants grow faster when they receive more light. Use the equipment shown in Figure 3.

State one factor that you would keep the same in this experiment.

A plant was kept at a very high temperature of 60C.

Explain the effect of this temperature on photosynthesis.

Figure 1 shows a bird called an egret on the back of a buffalo.

(Source: © Jaromir Chalabala/Shutterstock)

Figure 1

The egret eats parasites that live on the skin of the buffalo.

Which term describes this relationship, where the buffalo and the egret both benefit?

The buffalo is part of the carbon cycle.

Use words from the box to complete the sentences.

The buffalo gains carbon from the_........ in the plants that it eats.

Bacteria will_........ the waste from the buffalo.

Figure 2 shows part of the carbon cycle.

Draw and label an arrow on Figure 2 to show the process plants use to make glucose from carbon dioxide.

Enzymes are used to digest proteins.

Figure 3 shows an enzyme and a protein.

Explain how boiling the enzyme stops the protein being digested.

Respiration occurs in cells.

Why do cells respire?

An athlete runs every day as part of their training.

Explain why the breathing rate of the athlete increases when running.

When the athlete is running, their muscle cells use both aerobic respiration and anaerobic respiration.

State two differences between aerobic respiration and anaerobic respiration.

Bromothymol blue (BTB) solution is an indicator of pH.

Figure 2 shows the colour of BTB at different pH levels.

When air is passed through green BTB, for one minute, the solution stays green.

When a person breathes out through a straw into BTB for one minute the solution turns yellow.

Explain why the air breathed out turns the BTB solution yellow.

A scientist placed pondweed into two sealed test tubes containing green BTB solution.

Test tube A was kept in the dark. Test tube B was kept in the light. All other conditions were kept the same. Figure 3 shows these test tubes at the start of the investigation.

Figure 4 shows the colour of the BTB solution after 5 hours.

Explain the results for tube A and tube B shown in Figure 4.

Figure 6 shows a method of investigating the rate of photosynthesis in a water plant.

What are the products of photosynthesis?

The rate of photosynthesis can be measured by counting the number of bubbles of gas produced in one minute.

Figure 7 shows some results from this investigation in different light intensities.

Light intensity was changed by moving the lamp towards or away from the water plant.

Describe the effect of light intensity on the rate of photosynthesis. Use information from Figure 7 to help you.

The bubbles are different sizes and can be difficult to count.

Describe how the quality of the results from this investigation could be improved.

Describe how this investigation could be changed to find the effect of temperature on the rate of photosynthesis.

Increased nitrates can cause eutrophication in lakes.

Explain how eutrophication will affect the fish living in the lakes.

Figure 9 shows an area of woodland with some small plants growing in the ground between the trees.

(Source: © Maksym Holovinov/Shutterstock)

Figure 9

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 25 m² areas of the woodland.

Figure 10 shows the results.

Explain the effect of light intensity on the number of small plants per m².

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

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.

Figure 1 shows the leaves and flowers of water lily plants (Nymphaea odorata) on a lake.

Water lilies have stomata on the upper surface of the leaves.

Explain why water lilies have no stomata on the lower surface of the leaves.

The white petals of the water lily flowers cannot photosynthesise.

Which structure in leaf cells is the site of photosynthesis?

Glucose is made by photosynthesis.

Glucose is converted to another sugar to be transported in the plant.

What is the name of this sugar?

Describe how this sugar is transported from the leaves to the flowers of the water lily.

Figure 2 shows water lilies growing in a lake in Europe.

One water lily plant was brought from America 10 years ago and planted in the lake shown in Figure 2.

Explain why this non‑indigenous plant now covers the whole surface of the lake.

Figure 6 shows the global movement of carbon into or out of the atmosphere.

Calculate the net mass of carbon added to the atmosphere each year.

_........ gigatonnes

Joseph Priestley was a scientist who investigated how green plants and combustion affected the carbon cycle.

Figure 7 shows his first experiment.

State why the candle was not burning after three minutes.

Joseph Priestley continued the investigation but placed a plant inside the bell jar as shown in Figure 8.

He observed that the candle stayed alight for two minutes more than the candle in the bell jar in the first experiment.

Explain his observation.

State two variables that would need to be controlled to compare these two experiments.

Nitrogen is cycled through the environment.

Describe the roles of bacteria in the nitrogen cycle.