Chloroplasts

Double membrane

Stroma

• Jellylike fluid
• Contains enzymes which catalyse photosynthetic reactions
• Holds starch grains which are temporary stores of photosynthetic products

Thykaloids

• disc-like membranous sacs, large in number, stacks called grana
• provides large surface area to pack more chlorophyll
• grana are interconnected
• allows efficient transport of photosynthetic products within the chloroplast

Photochemical reactions

• Location: thylakoid

Light absorption

1. Light energy is absorbed by chlorophyll
2. Electrons are excited
3. Excited electron releases energy when passing through electron transport chain

Photophosphorylation(Synthesis of ATP)

\ce{ADP +P ->[energy]ATP}

ADP: adenosine diphosphate
ATP: adenosine triphosphate

Photolysis of water

\ce{2H2O->4H+ + 4e- + O2}

\ce{H+: NADP +H+->NADPH}$\ce{H+: NADP +H+->NADPH}$
\ce{O2:}$\ce{O2:}$ Released as gas (byproduct)

Calvin cycle

graph TD;
    5-C_compound-->|+CO2|3-C_compound;
    3-C_compound-->|ATP->ADP+P, NADPH-> NADP|Triose_phosphate;
    Triose_phosphate-->Glucose;
    Triose_phosphate-->|ATP->ADP+P|5-C_compound;

Overall photosynthesis

\ce{6CO2 +6H2O ->[light captured][by chlorophyll] C6H12O6 +6O2}

Factors affecting photosynthesis

1. Light intensity
2. Carbon dioxide concentration

Regulation of photosynthetic rate

Fate of the products

Carbohydrates

Glucose: energy source
Starch: storage
Sucrose: transport
Cellulose: building cell walls

Lipids

Fatty acids

Proteins

Signficance of photosynthesis

1. Providing the basic food source in ecosystems

2. Maintaining energy flow in ecosystems

3. Maintaining oxygen and carbon dioxide balance