Light reactions in plants
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Light is fundamentally important to all plants as it is the primary source of their energy. It is quite clear that the light reactions have a large and significant role to play in the photophosphorylation. I will first go into the background of the light reaction and explain what is meant by photophosphorylation . I will also give background information on light, (as a source of energy and show how the difference between the two light reactions, in respect to the wavelength of light they utilise. I will also include a small section on chloroplasts and pigments.
Light Reactions
The central reactions of photophosphorlyationsynthesis take place in the chloroplasts of a photosynthetic cell. There are two stages to the light reaction; PS1 and PS2.
First light of a certain wavelength is trapped by the chloroplasts and converted into chemical energy by a series of reactions, these reactions take place in the internal membrane of the chloroplast.
PS2 is the first of the light reactions to occur and it involves the splitting of H2O by phytochrome 680 + light which results in ATP production and 2e-, these electrons are then carried by the PQ molecule, which then goes on to pass the 2e- to PC, which then in turn follows to FD by excitement by light (PS1) (photophosphorlyationnphoton) of phytochrome 700 (which absorbs light at wavelength of 700nm) to produce NADPH; so both oxidative and reductive processes have occurred.
PS1 occurs in the non apressed membranes of the thylakoids...