5.6.4(The light-independent reaction)

Describe the role of carbon dioxide

• Carbon dioxide is the course of carbon for the production of organic molecules

• Used for carbon fixation in the stroma

Describe how CO2 gets from the air into the chloroplasts

• Carbon dioxide from air diffuses into leaf, through airspaces to spongy mesophyll

• It then diffuses through the cell wall down a concentration gradient, into the cell then through the chloroplast envelope and into the stroma

Name the 4 stages of the Calvin cycle

1. Carbon fixation

2. Reduction

3. Synthesis

4. Regeneration

Describe the Calvin cycle

1. Carbon dioxide combines with ribulose bisphosphate(RuBP). This reaction is catalysed by ribulose bisphosphate carboxylase(RuBisCO)

2. RuBP after accepting the CO2 becomes carboxylated which forms an unstable 6 carbon intermediate that breaks down

3. Breaks down into 2 glycerate phosphate(GP) molecules - 3 carbon molecule

4. GP is then reduced, using Hs from reduced NADP to form Triose phosphate(TP). energy from ATP is broken down to ADP + Pi

5. TP is then either used to be synthesis Lipids, glucose or amino acids. Or TP is converted back into RuBP with the addition of phosphate from the break down of ATP to ADP + P

Explain why the calvin cycle only runs during the day

• This is because reduced NADP can be only be generated during the light dependent stage

• If no NADP is present, then no hydrogens are used to convert GP to TP and so the cycle would stop

• RuBisCo is activated using ATP with is only generated using LDR

Describe the uses of Triose phosphate

• Some glucose is converted to sucrose, some to starch and some to cellulose

• Some TP is used to synthesise amino acids, fatty caids and glycerol

• TP is recycled to regenerate RuBP

List all the reactants and products of the LIR in one cycle

• 1 CO2 is used

• 2 NADP are returned to the LDR

• 3 ATP are used

State and explain how many cycles are needed to make 1 glucose molecule

• 6 Turns are needed

• This is because only 1 carbon from the triose phosphate is used for the synthesis of glucose and glucose contains 6 carbons