Light Independent Reaction

Where does the Calvin cycle take place?

In the stroma

What does the Calvin cycle require?

ATP and NADPH from the light dependent reactions

Why is the Calvin cycle also known as carbon dioxide fixation?

Carbon from CO2 is fixed into an organic molecule

Describe the process of the Calvin Cycle

1. CO2 is combined with RuBP (reaction is catalysed by the enzyme RUBISCO)

2. Forms an unstable 6C molecule which quickly breaks down into two 3C molecules (GP)

3. ATP is hydrolysed to release energy

4. This energy is used to convert GP into GALP (3C) - NADPH reduces GP into GALP

5. NADPH is oxidised into NADP

6. Some GALP is converted into useful organic compounds like glucose while some continues to regenerate RuBP for the next cycle (1C into glucose while 5C into RuBP)

7. Regenerating RuBP requires 5C and the rest of the ATP previously produced by the light dependent reactions

How might CO2 enter the chloroplast?

Enters through the stomata and infuses into the stroma

Why would it take 6 cycles to produce glucose?

Every cycle only donates 1C into making a useful organic compound (glucose)

The other 5C are used to regenerate RuBP

Glucose is a 6 carbon molecule

What can 2 GALP molecules be used to create?

A hexose sugar (6C sugar)

What other substances can the Calvin cycle be used to make?

• Carbohydrates - 2 GALP molecules can join to form hexose sugars - hexose sugars joined into a chain would create a polysaccharide

• Lipids - glycerol can be made by combining GALP and fatty acids

• Amino acids - can be made form GP

• Nucleic acids - Ribose for RNA can be made from GALP