Where does photosynthesis happen? Be specific.

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trophyhunter1 eNotes educator| Certified Educator

Specifically, organelles known as chloroplasts are the site of photosynthesis for green plants and algae. Any part of the plant that appears green contains chloroplasts. They are mainly located in the leaves where most of the photosynthesis occurs.

In the center of the leaf, an area known as the mesophyll contains cells which are packed with chloroplasts. They usually have between 30-50 chloroplasts per cell. 

The structure of the chloroplast is a double membrane around a thick fluid known as the stroma. In the stroma is an internal membrane system known as the thylakoid. Inside this membrane is a space called the thylakoid space. The thylakoids look like a stack of dinner plates and each "stack" is known as a grana.

The green pigment called chlorophyll can be found in the thylakoid membranes. This pigment absorbs light energy to be used in the photosynthetic reactions.

Photosynthesis begins when light is absorbed by chlorophyll. This energy is used to produce chemical energy in the form of ATP and NADPH. Also, water is split into hydrogen and oxygen. The oxygen is released out of pores in the leaf called stomates. This occurs during the light reaction.

Next, the light-independent reaction (Calvin cycle) occurs. Here, carbon dioxide is fixed when it becomes incorporated into the organic compound of glucose sugar. 

The light reaction occurs in the thylakoid membranes and the Calvin cycle, which is the light-independent reaction, occurs in the stroma. Both of these areas can be found in the chloroplast, the site of photosynthesis.

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