Photosynthesis (Edexcel A (SNAB) A Level Biology)

Adenosine triphosphate is an important molecule for photosynthesis.

Write an equation to show how adenosine triphosphate is synthesised from adenosine diphosphate.

(1)

The diagram below shows a molecule of ATP.

ATP is commonly regarded as the 'energy currency' in cells.

On the diagram, circle the chemical bond that, when broken, yields a large amount of energy to fuel cellular processes.

(1)

The human body is believed to utilise the energy stored in around 150 mol of ATP per day. The molecular weight of ATP is 507. This makes the mass of ATP utilised per day by the human body around 76 kg. The mass of a typical adult male is 80 kg.

The mass of ATP in the human body is typically 250 g at any one time. 

Use the information and your own knowledge to explain how such a large mass of ATP is used per day.

ATP is one of the products of the light-dependent stage of photosynthesis.

Name the other product of this stage.

Place these parts of a photosynthetic plant cell into a logical sequence based on size.

1.  ____________________
2.  ____________________
3.  ____________________
4.  ____________________
5.  ____________________
6.  ____________________

When plants are exposed to extremely high or cold temperatures for a continued period of time, they are put under a lot of stress.

This stress greatly impacts the rate of photosynthesis, in particular the rate of the light-dependent reactions of photosynthesis.

Aside from the general effect of cold temperatures on enzyme-controlled reactions, explain why extreme cold leads to a decrease in the rate of the light-independent reaction.

State where the light-independent reactions take place in photosynthetic plants.

Extreme cold can also cause a decrease in the activity of the enzyme rubisco.

A decrease in the activity of rubisco limits the rate of photosynthesis.

Explain why.

A team of researchers isolated two enzymes from the leaf cells of tomato plants: rubisco and rubisco activase.

Rubisco activase is an enzyme that activates rubisco.

They investigated the effect of temperature on the two enzymes.

The graphs below show their results.

The researchers concluded that extreme heat reduces the activity of rubisco in plant leaves by affecting rubisco activase.

Use the information given in the graphs to evaluate this conclusion.

The diagram shows some of the reactions that take place inside a palisade mesophyll cell.

Identify substances A, B and C.

A. ..............................................

B. ..............................................

C. ..............................................

Describe how carbon dioxide reaches the inside of a palisade mesophyll cell from the external atmosphere.

In the light-independent reactions of photosynthesis, carbon dioxide undergoes a process of fixation. 

State what is meant by the term 'fixation' in this context.

Ribulose bisphosphate oxygenase-carboxylase (rubisco) is the most abundant enzyme on the planet. There are thought to be around 32 megatonnes (3.2 × 10¹⁰ kg) of rubisco on Earth.

Rubisco is an inefficient enzyme; this goes some way to explaining why plants contain so much of it in order to perform its function as a catalyst.

Rubisco from millions of years ago is believed to have been a better-functioning enzyme due to the increased levels of CO₂ present in the atmosphere at that time in the Earth's history. 

At high temperatures and low CO₂ levels, rubisco can also catalyse a reaction called photorespiration, in which oxygen is the substrate and CO₂ is the product. Photorespiration, like its conventional version of straightforward respiration, is an exothermic process.

Using this information and your knowledge, predict the effects of 21^st Century climate change on the activity of rubisco.

Apart from their cyclic and non-cyclic nature, compare and contrast the processes of cyclic and non-cyclic photophosphorylation in the light-dependent stage of photosynthesis.

Write a balanced symbol equation that summarises the photolysis of water.

You do not need to include state symbols.

State precisely the location of photosynthetic pigments within a chloroplast.

Certain intermediates from the Calvin cycle can enter other biochemical pathways. 

Which statements from I. to IV. are true about the role of photosynthetic intermediates in the synthesis of non-carbohydrate biological molecules?

1. Glycerate-3-phosphate (GP) is used in the synthesis of nonessential amino acids.
2. Glyceraldehyde-3-phosphate (GALP) is used in the synthesis of DNA and RNA.
3. Glyceraldehyde-3-phosphate (GALP) is used in the synthesis of fatty acids.
4. Glycerate-3-phosphate (GP) is used in the synthesis of glycerol.