The molecules used in photosynthesis are stored in different parts of the chloroplast before they are used. The key molecules ATP and NADPH, which carry energy, are produced in the thylakoid membranes during the light-dependent reactions and stored there temporarily. The carbon dioxide and other molecules needed for the Calvin cycle (light-independent reactions) are stored and processed mainly in the stroma, which is the fluid-filled space surrounding the thylakoids inside the chloroplast. Additionally, sugars produced as intermediates like glyceraldehyde 3-phosphate can be further converted into starch and stored as large grains in the stroma for later use. In summary:
- ATP and NADPH are generated and stored in the thylakoid membranes.
- CO2 and other molecules for the Calvin cycle are processed in the stroma.
- Starch, a carbohydrate reserve, is stored as grains in the stroma.
Hence, before molecules are used in photosynthesis, critical energy molecules are held in the thylakoid membranes, and carbon compounds are stored in the stroma of the chloroplast.
