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Where does photosynthesis take place ?

Open the chloroplast Photosynthesis takes place in the chloroplasts of higher photosynthetic organisms like a tree. Some Bacteria however have no chloroplasts but photosynthetic membranes within their cells.

What does photosynthesis require ?

Photosynthesis requires light energy which is captured by special pigments, most notably chlorophyll. This energy is used to create energy-rich carbohydrate molecules (sugar and starch) out of carbon dioxide (CO2) and water (H2O). During this process oxygen (O2) is released as a by-product. All the oxygen in the Earth's atmosphere which is used by animals and plants for respiration, originates as a by-product of  photosynthesis.

The process may be summed up in the following formula : CO2 + 2H2O  >>   CH2O + O2 + H2O

Photosynthesis has two major processes

Photosynthesis may be subdivided into two major processes:

The light dependent reactions require sunlight so as to utilise its energy to produce the energy-rich molecules ATP and NADP. This phase of photosynthesis is also known as the light phase as it requires light energy.

The light independent reactions utilise the energy-rich molecules ATP and NADP which were produced in the light phase. The ATP and NADP are used  to produce energy-rich carbohydrate molecules (simple sugars) which can be stored and used as a basis for all other forms of organic molecules. This phase of photosynthesis is also known as the Calvin cycle or dark phase as it does not require light energy.

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