Where does the Calvin cycle take place in chloroplasts?

Where does the Calvin cycle take place in chloroplasts?

• A. Stroma
• B. Thylakoid membranes
• C. Mitochondrial matrix
• D. Cytoplasm

Answer: (B)

The Calvin cycle happens in the stroma, the fluid-filled space inside the chloroplast surrounding the thylakoid membranes. After the light-dependent reactions in the thylakoid membranes produce ATP and NADPH, these energy carriers move into the stroma to power carbon fixation and sugar synthesis. In the stroma, carbon dioxide is fixed by the enzyme Rubisco to RuBP, forming 3-phosphoglycerate, which is then reduced to glyceraldehyde-3-phosphate using ATP and NADPH. The cycle regenerates RuBP so it can continue, building sugars later used to make glucose and other carbohydrates. The stroma provides the enzyme-rich environment for these reactions, while the thylakoid membranes handle the light reactions. Mitochondrial matrix and cytoplasm are in different parts of the cell, not within the chloroplast.

The Calvin cycle happens in the stroma, the fluid-filled space inside the chloroplast surrounding the thylakoid membranes. After the light-dependent reactions in the thylakoid membranes produce ATP and NADPH, these energy carriers move into the stroma to power carbon fixation and sugar synthesis. In the stroma, carbon dioxide is fixed by the enzyme Rubisco to RuBP, forming 3-phosphoglycerate, which is then reduced to glyceraldehyde-3-phosphate using ATP and NADPH. The cycle regenerates RuBP so it can continue, building sugars later used to make glucose and other carbohydrates. The stroma provides the enzyme-rich environment for these reactions, while the thylakoid membranes handle the light reactions. Mitochondrial matrix and cytoplasm are in different parts of the cell, not within the chloroplast.