1. Photosynthesis Processes

2. Overview Absorption of light energy Conversion to chemical energy
Sun hits chloroplasts
Conversion to chemical energy
Light dependant reaction
Storage of energy in sugars
Light independent reaction

3. 2 Stages of Photosynthesis
Light Dependant Reaction
Takes place in Grana (thylakoid membrane)
Products – ATP, O₂, NADPH
Light Independent Reaction – Calvin Cycle
Takes place in the stroma
Products – Glucose, NADP⁺, ADP

4. Light Dependant Reaction
Takes place in thylakloid membrane of the chloroplast

5. Light Dependant Reaction

6. Light Dependant Reaction
Light strikes PSII
2 electrons are excited
Simultaneously - H₂O split into to H⁺ and ½ O₂ (photolysis)
Electrons flow down ETC (electron transport chain)
Providing energy for production of ATP
Electrons enter photosystem I
Light strikes PSI
Exciting electrons
Electrons flow down to NADP⁺ electron acceptor
Provide energy for production of NADPH (used in light independent reactions)
NADPH = nicotinamide adenine dinucleotide phosphate

7. Light Dependant Reaction

8. Light Independent Reactions Calvin Cycle
No light required
Carbohydrates are synthesized from CO₂ using the ATP and NPDH formed in light reactions

9. Calvin Cycle 4 Steps Carbon Fixation Energy conversion
Release one molecule of sugar G3P
Regeneration of RuBP

10. Calvin Cycle Step 1 – Carbon Fixation
Three molecules of CO₂ combine with 5-C sugars RuBP (Ribulose biphosphate)
Enzyme is Rubisco
Each CO₂ forms a 6-C molecule which splits into two 3-C acids (PGA)
For 3 co2 6 PGA result

11. Calvin Cycle Step 2 – Energy Conversion 2 chemical reactions
Use 6 molecules of ATP
ATP ADP + P
And
Use 6 molecules of NAPDH
NADPH NADP⁺
Producing 6 molecules of 3-C sugar G3P (phosphoglyeralehyde)
G3P always

12. Calvin Cycle Step 3 – Release one molecule of G3P
Five of the G3P molecules remain in the cycle
One G3P molecule in released as a product
Two G3P molecules needed to make one molecule of glucose

13. Calvin Cycle Step 4 – Regeneration of RuBP
Series of chemical reactions
Use 3 ATP to convert 5 G3P molecules into 3 RuBP molecules
5 molecules of G3P = 15 carbons
3 molecules of RuBP = 15 carbons
Show animation

14. Calvin Cycle
Takes two molecules of G3P to produce one molecule of glucose So
6 molecules of CO₂
18 molecules of ATP
12 molecules of NADPH

15. Photosynthesis Recap