LIR (5.8)

Question 1

State the precise site of the light independent reactions

Answer 1

The LIR occurs in the Syrian fluid of chloroplasts

Question 2

State the alternate name for the light independent reactions

Answer 2

The alternative name is the Calvin cycle

Question 3

) The light independent reactions can be divided into three interlinked reactions:
carbon fixation, reduction and phosphorylation.
3(i) Describe what happens in carbon fixation
3(ii) Describe what happens in reduction
3(iii) Describe what happens in phosphorylation

Answer 3

During fixation carbon dioxide is fixed to RuBP which ultimately produces GP.
During reduction ATP and reduced NADP are reduced into ADP and NADP which helps convert GP into GALP
In the phosphorylation stage ATP is used to convert remaining GALP into RuBP so the cycle can start again

Question 4

Describe the process of the light independent stage (typical 4/5 marker)

Answer 4

Carbon dioxide enters Calvin cycle and is fixed with RuBP in order to produce GP.
GP becomes reduced from the conversions of reduced NADP to NADP and ATP to ADP.
This converts GP into something called GALP, where some GALP molecules are used to produce organic molecules (amino acids, lipids, carbohydrates, etc)
Remaining GALP undergoes phosphorylation to convert it back to RuBP so it can be fixed to carbon dioxide again

Question 5

Describe how the products of the light independent stage can be used to produce cellulose cell walls

Answer 5

During the Calvin cycle, after reduction, GALP is produced. Two of these GALP molecules exit the cycle and are used to create organic molecules such as glucose. If enough glucose is produced, chains can be formed to produce cellulose which can be used in cell walls.

Question 6

6) Explain why the light independent stage relies on the light dependent stage occurring

Answer 6

The LIR relies on the chemical energy built up from the LDR to help the fixation of carbon dioxide to produce glucose molecules.