Chloroplasts

The chloroplasts are lens-shaped organelles found in leaves and other green organisms. In the green tissue, in the interior of the leaf, are mesophyll. Each mesophyll has about 30 or 40 chloroplasts. Chloroplasts are made up of saclike photosynthetic membranes. These membranes are in such an order that they form stacks called grana. Next to the grana are thylakoids which separate the grana from the stroma, the fluid out side the thylakoid. Inside the grana are the pigments involved in photosynthesis. The pigments in the chloroplast are called chlorophyll.

The chloroplasts main function is to trap solar energy and to use it to form carbohydates. They are the site of photosynthesis, which is the basic food source for the organism. When a fruit ripens, the chloroplasts in the green tissue are changed to nonphotosynthetic organelles and turn color. This is what shows that they are actually ripened. Chloroplasts can also come from the division of other chloroplasts; this can happen because they contain their own DNA molecules. How do the chloroplasts convert light energy to the chemical energy stored in organic molecules? The overall photosynthetic equation has been known since the 1800's: In the presence of light, the green parts of plants produce organic material and oxygen from carbon dioxide and water. The chemical equation for photosynthesis: 6CO₂ + 12H₂O + Light Energy ----> C₆H₁₂O₆ + 6O₂ +6H₂O.

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