Photosynthesis (Edexcel International A Level Biology)

The following equation summarises photosynthesis.

6CO₂ + 6H₂O ⟶ C₆H₁₂O₆ + 6O₂

The diagrams show the bonds in carbon dioxide, water and oxygen.

Energy is needed to break chemical bonds, and to form new chemical bonds. This is called the bond energy.

The table shows some bond energies for the bonds in carbon dioxide, water, glucose and oxygen.

In photolysis, one of the bonds in each water molecule is broken.

Using the equation for photosynthesis, calculate how much energy is released by photolysis in order for one molecule of glucose to be made.

(1)

Explain how light energy is converted into chemical energy in the form of ATP.

(4)

The diagram shows the structure of glucose.

The energy needed to form the bonds in one molecule of glucose is 9164 kJ.

State what other information is needed in the table of bond energies for this value to be calculated.

(1)

Where in the chloroplasts are these bonds formed?

(1)

Glucose is used by plants in the production of amino acids.

(i)

Which row of the table describes how two amino acids join together?

(1)

Explain why amino acids cannot be produced from glucose alone.

(2)

Photosynthesis consists of the light-dependent reactions and the light-independent reactions.

In the light-dependent reactions, light energy is converted into energy stored in ATP.

An equation can summarise the production and breakdown of ATP.

Complete this equation, by writing the names of the substrates and the type of reaction on the three dotted lines provided.

The light-independent reactions use products of the light-dependent reactions to produce simple sugars.

Which row of the table shows the products of the light-dependent reactions that are used in the light-independent reactions?

Simple sugars have the formula C_nH_2nO_n.

Name the inorganic molecule from which each element in a simple sugar originated.

Simple sugars are used in the synthesis of new biological molecules.

Which row of the table shows the inorganic ions that are needed to synthesise these new biological molecules?

(3)

Chloroplasts and mitochondria are two organelles found in some plant cells.

Compare and contrast the structure of a chloroplast with the structure of a mitochondrion.

The light-dependent reactions of photosynthesis can result in either cyclic or non-cyclic photophosphorylation.

(i)

The diagram shows cyclic photophosphorylation.

Complete the diagram by writing the correct word or words on the dotted lines, labelled D, E, F, G and H.

(3)

Name one molecule that is produced in non-cyclic photophosphorylation that is not produced in cyclic photophosphorylation.

(1)

(iii)

Describe the role of photolysis in non-cyclic photophosphorylation.

(2)

The structure of a chloroplast is related to its role in photosynthesis.

The diagram shows a chloroplast.

Which row in the table identifies the structures labelled P, Q and V?

(1)

Which structure contains GALP?

(1)

A copy of the printed diagram, set against a ruler scale, has been provided below for your use in this question.

The length of this chloroplast is 7.5 μm.

Calculate the magnification of this diagram. 

(1)

Structures T and U are membranes.

Compare and contrast the structure of these two membranes.

(3)

An investigation studied the effect of periods of light and dark on the levels of chloroplast DNA in one species of a single-celled organism.

One group of these organisms, group A, was exposed to 36 hours of continuous light.

The other group of these organisms, group B, was exposed to 12 hours of light, followed by 12 hours of darkness, followed by 12 hours of light.

The graph shows the results of this investigation.

These organisms divide by mitosis followed by cell division, during the dark.

Describe two conclusions that can be made about the replication of chloroplast DNA.

Thylakoid membranes contain chloroplast pigments and molecules of ATP synthase.

These membranes are the site of the light‐dependent reactions.

The graph shows the absorption spectrums of two chloroplast pigments from one plant.

Draw the action spectrum for this plant on the axes below.

(2)

Calculate how many times greater the percentage of light absorbed by chlorophyll b is than that absorbed by chlorophyll a, at their maximum absorptions.

(1)

(iii)

Thylakoid membranes contain different types of chlorophyll pigment.

Explain the advantage of this for a plant.

(2)

The ATP synthase molecules are proteins.

Which row of the table describes the bonds that form between amino acids in a protein?

(1)

Products of the light‐independent reactions are used to synthesise amino acids.

Describe how plants synthesise amino acids.

(2)

Seaweeds are a group of organisms that carry out photosynthesis.

Identifying the types and proportions of chlorophyll pigments is important in the classification of seaweeds and biodiversity studies.

State the meaning of the term biodiversity.

Explain the role of chlorophyll in the light-dependent reactions of photosynthesis.

An investigation compared the effectiveness of two solvents, propanone and DMSO, in extracting photosynthetic pigments.

Four species of seaweed were collected from the Indian coast of Tamil Nadu and taken to the laboratory where the species were identified.

Each species of seaweed was split into two samples of equal mass.

The photosynthetic pigments were extracted from each sample using one of the two solvents and their concentrations determined.

The graphs show some of the results of this investigation.

Discuss the effectiveness of these extraction methods in the identification of these species.

Use the information in the graphs to support your answer.

(6)

(ii)

Suggest why different concentrations of chlorophyll were obtained using these two different solvents.

(2)

The table gives some information about structures found in chloroplasts.

Where in the chloroplast is RUBISCO active?

(1)

What is stored in S?

(1)

Where is GP formed?

(1)

Which is the correct order of size, smallest to largest?

(1)

The graph shows the rate of photosynthesis in two types of plant, Spartina and Leucopoa, at different temperatures.

Which could be the units for rate of photosynthesis?

(1)

Compare and contrast the rate of photosynthesis of these two species of plant, at different temperatures.

(3)

(iii)

Describe how a Q₁₀ value for the rate of photosynthesis can be calculated, using this graph.

(2)

The graph shows the maximum temperature, for each month, in two regions of North America: Wheatland and Pole Mountain.

Explain in which of these two regions of North America Spartina is most likely to grow.

Use the information in both graphs to support your answer.

(3)