Question

In the initial step in carbon fixation, a molecule of CO2 is attached to RuBP to produce a six-carbon molecule, which is immediately split to produce two molecules of 3-phosphoglycerate. After phosphorylation and reduction produces glyceraldehyde 3-phosphate (G3P), what more needs to occur to complete the Calvin cycle?

Answer 1

Carbohydrate needs to be synthesized and Rubisco needs to be regenerated.

Step-by-step explanation:

The Calvin cycle is a series of reaction leading to the fixation of carbon dioxide during the process of photosynthesis. It is sometimes referred to as dark reaction or light independent reaction of photosynthesis.

The cycle can be broken down into 3 major steps:

• Fixation of carbon by Rubisco leading to the formation of a short-lived, 6 carbon intermediate that immediately splits to give two molecules of 3-phosphoglyceric acid.
• Reduction stage during which the 3-phosphoglyceric acid produced at the initial stage is converted to glyceraldehyde-3 phosphate.
• Carbohydrate formation stage which involves the synthesis of glucose using some of the glyceraldehyde-3 phosphate produced during reduction stage.
• Regeneration phase involves the regeneration of Rubisco using the remaining portion of the glyceraldehyde-3 phosphate produced at the reduction stage.

Hence, to complete the Calvin cycle, glucose needs to be synthesize and Rubisco needs to be regenerated from glyceraldehyde-3 phosphate produced during the reduction stage.

Answer 2

Regeneration is the final step

Step-by-step explanation:

Part of the G3P molecules will leave the Calvin cycle to form a carbohydrate molecule, which is usually glucose (C6H12O6). Carbohydrate molecule has six carbon atoms, so it will take six turns of the Calvin cycle to make one carbohydrate molecule (one for each carbon dioxide molecule fixed). The remaining G3P molecules will regenerate RuBP. ATP will be used in the regeneration of RuBP. This enables the cycle to prepare for the carbon-fixation step.