During which stage of photosynthesis carbon dioxide is reduced to carbohydrate?

The stage of photosynthesis during which carbon dioxide is reduced to carbohydrate is the Calvin Cycle, also known as the light-independent reactions or dark phase. Here are the steps:

1. Carbon Fixation: The enzyme RuBisCO catalyzes the reaction between carbon dioxide and Ribulose-1,5-bisphosphate (RuBP), a 5-carbon sugar, to form a 6-carbon compound. This compound quickly splits into two molecules of 3-phosphoglycerate.

2. Reduction: ATP and NADPH from the light-dependent reactions are used to convert 3-phosphoglycerate into glyceraldehyde 3-phosphate (G3P), a carbohydrate.

3. Regeneration: Some G3P molecules are used to regenerate RuBP, allowing the cycle to continue.

4. Carbohydrate Synthesis: The remaining G3P molecules can be used to make glucose and other carbohydrates.

So, the reduction of carbon dioxide to carbohydrate primarily occurs in the Calvin Cycle of photosynthesis.