Photosynthesis

3 Adaptations of Chloroplasts

• Grana has a large surface area for the attachment of chlorophyll, electrons and enzymes

• Granal membrane has ATP synthase channels and are selectively permeable so a proton gradient can be formed and ATP can be synthesised

• Chloroplasts contain DNA and ribosomes allowing them to synthesise proteins needed in the light dependent reaction

Processes in the light-dependent reactions

1. Photoionisation

2. Photolysis

3. Electron Transport Chain

4. Movement of H⁺ ions

5. Chemiosmosis

6. Reduction of NADP

Photoionisation

Light hits chlorophyll molecules in PSII, exciting electrons

Photolysis of water (equation and destination of each produce)

H₂O → 2H⁺ + 2e^- + 0.5O₂

H⁺ - chemiosmosis

O₂ - respiration/release

e^- - replace those lost by chlorophyll

Chemiosmosis (describe + equation)

H⁺ ions diffuse back into the stroma via ATP synthase channels

ADP + P_i → ATP

Reduction of NADP equation

NADP + H⁺ + e^- → NADPH

Calvin cycle description

1. CO₂ is added to a 5C ribulose biphosphate (RuBP) using rubisco enzyme

2. RuBP splits into 2 3C glycerate-3-phosphate molecules (GP)

3. Each GP molecule is reduced to a 3C triose phosphate (TP) using energy from ATP hydrolysis and oxidation of NADPH

4. The 2 TP molecules re-form RuBP. One C is kept for forming organic molecules

5. Every 6 turns, 1 glucose molecule is formed.

Order of formation in Calvin cycle (+ numbers)

RuBP → 2GP → 2TP → RuBP