All plants are capable of producing their own organic material in the form of carbohydrates, from water, carbon dioxide and the energy from light. This is photosynthesis, which takes place in the chloroplasts of chlorophyllous cells.
Photosynthesis is the succession of two coupled phases:
- Photochemical reactions: these reactions take place in the thylakoids where light energy is captured by the pigments and converted into chemical energy in the form of intermediate compounds (ATP and NADPH + H+). These reactions consume water (H2O) and liberate dioxygen (O2).
- Biochemical reactions (Calvin Cycle): in the stroma, carbon dioxide (CO2) is used to synthesize carbohydrates from the chemical energy produced by the preceding phase (use of intermediate compounds).
A chloroplast is bounded by an envelope (two membranes) enclosing a liquid called the stroma. Within the stroma rests a network of lamellae, the thylakoids. Some of these are grouped into piles,…