Photosynthesis (SQA National 5 Biology): Exam Questions

The graph shows the effect of limiting factors on the rate of photosynthesis.

Which row in the table identifies the limiting factors at points X and Y on the graph?

An experiment into photosynthesis was carried out.

After the lamp was switched on, the time taken for the leaf disc to float to the surface was recorded.

The experiment was repeated five times and the results are shown in the table.

Calculate the average time taken for the leaf disc to float to the surface.

.......................seconds

A gas produced during the first stage of photosynthesis diffuses out of the cells, causing the leaf discs to float to the surface.

Name this gas.

During photosynthesis the light energy from the lamp is converted into chemical energy.

Name the molecule generated by this chemical energy that is then used in the second stage of photosynthesis.

The second stage of photosynthesis is affected by temperature.

Name this stage and give a reason.

Stage.............................................................................................................

Reason...........................................................................................................

In an investigation into photosynthesis, a green plant was set up as shown and left in the light for 2 days.

Leaves P, Q and R were then tested for the presence of starch.

In which of the leaves was starch present?

An experiment was carried out to investigate the effect of carbon dioxide concentration on the rate of photosynthesis. The rate of photosynthesis was measured by recording the mass of sugar produced per hour.

(i) Describe the relationship shown between carbon dioxide concentration and the mass of sugar produced.

[2]

(ii) Suggest one factor that could be limiting the rate of photosynthesis at point X in the graph.

[1]

(i) Hydrogen is a product of the light reactions and is required for carbon fixation.

Describe how this hydrogen is produced.

[1]

(ii) The sugar produced during the carbon fixation stage can be converted into other substances, such as starch.

Name one other substance sugar can be converted into and state its role in the cell.

Substance .........................................................................................................

Role....................................................................................................................

An experiment was set up to investigate the effect of changing carbon dioxide concentration on the rate of photosynthesis.

The results are shown in the graph.

Which of the following factors could be limiting the rate of photosynthesis at point X?

Photosynthesis is a two‑stage process that takes place in the leaves of green plants.

State the source of energy for the first stage.

(i) Name the process by which oxygen moves out of the leaf through stomata.

[1]

(ii) The number of stomata on both surfaces of five leaves was counted and averages calculated.

The results are shown in the table.

Complete the table to include the number of stomata on the lower surface of leaf 5.

[1]

(iii) Name a substance that enters the leaf through stomata.

[1]

(i) Describe how sugar is produced in the second stage of photosynthesis.

[1]

(ii) Name one substance that the sugar produced could be converted into.

[1]

Which row in the table describes changes in conditions that may improve the growth of plants in a greenhouse?

An experiment was carried out to investigate the effect of green light on the rate of photosynthesis in the pondweed, Elodea.

Which of the following changes would provide a suitable control for this experiment?

When light is absorbed by a plant, photosynthesis takes place and as a result substance K is released from the leaves.

Name substance K.

Describe the energy change that takes place during the first stage of photosynthesis.

The graph shows the effect of increasing light intensity on the rate of photosynthesis at two different temperatures. All other factors were kept constant.

Identify the limiting factor at each of the points M and N.

M...........................................................................................................................

N............................................................................................................................