Photosynthesis: Thylakoid membrane and the Stroma

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thylakoid and stroma

The Main Steps of photosynthesis are compartmentalized into different regions of the chloroplast:

Thylakoid menbrane and compartment: The light reactions take place in the thylakoid membrane and thylakoid compartment and are concerned with the initial conversion of light energy into chemical energy stored in ATP and NADPH. The NADPH and the ATP feed into the Calvin cycle in the Chloroplast stroma where the ATP provides energy for molecular rearrangements and the electrons and hydrogen ion carried by the NADPH are transfered to the organic molecules involved in the Calvin cycle.

Stroma. The Dark reactions, mainly the Calvin cycle take place in the substance surrounfing the thylakoids. In the Calvin cycle, carbon from carbon dioxide is brought into the cycle as a source of carbon. Then after a series of molecular rearrangements, in part powered by ATP, the electrons and hydrogen ions from the NADPH produced in the light reactions are added to the molecules in the Calvin cycle yielding the three carbon phosphate sygar, PGAL.

The PGAL is used to make  glucose and other carbohydrates for the plant.

In the diagram, the yellow arrows represent light(photons), the purple arrows, the flow of the high energy electrons through the photosystems(green ovals) and the electron transport system blue-green rounded rectangles. The mushroom shaped blue structures represent ATP synthase channels.

pgd created 02/19/00 

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