Explain the processes of light and dark reaction in plants during photosynthesis.

Asked by nehajb | 3rd Jul, 2008, 09:26: PM

Expert Answer:

Light reaction is an energy trapping, photochemical reaction, taking place in the grana of chloroplast and resulting in the formation of ATP and NADPH2. During light reaction, chlorophyll absorbs energy, gets excited and releases a high energy electron which passes through a system of electron acceptors. During this electron transfer, energy is released in the form of ATP.

In dark reaction, CO2 is reduced to -arbohydrates. This reaction takes place in stroma of chloroplasts. It is independent of light. Here, ATP and NADPH2 is utilized.

In light reaction, there are 2 pathways of electron transfer, which are cyclic and non-cyclic electron transfer. During non-cyclic electron transfer, photolysis of water takes place. Under the influence of light, water molecule splits into H+ and OH-. Photolysis results in the generation of free oxygen (O2). This process is responsible for generating the majority of breathable oxygen in earth's atmosphere.

Answered by  | 4th Jul, 2008, 10:08: AM

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