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What are the stages of the Calvin-Benson cycle? Select all that apply.

A. Rubisco is used to convert PGA molecules to PGAL.
B. Most of the PGAL is used to regenerate RuBP, but some is exported to the cytoplasm to produce carbohydrates.
C. Rubisco attaches CO2 to a five-carbon organic compound called RuBP.
D. The resulting unstable six-carbon molecule splits into two three-carbon molecules of PGA.
E. ATP and NADPH are used to convert PGA molecules to PGAL.

Answer :

Final answer:

The Calvin-Benson Cycle consists of three key stages: Carbon Fixation, Reduction, and Regeneration. In this process, CO2 is fixed into organic compounds, and energy from ATP and NADPH is used to convert PGA into G3P. Finally, some G3P is utilized to regenerate RuBP to continue the cycle.


Explanation:

The Stages of the Calvin-Benson Cycle

The Calvin-Benson cycle, also known as the Calvin cycle, has three main stages: Carbon Fixation, Reduction, and Regeneration. Each stage plays a crucial role in transforming carbon dioxide into glucose, which plants use for energy.

1. Carbon Fixation

In the first stage, the enzyme RuBisCO catalyzes the attachment of carbon dioxide (CO2) to a five-carbon compound called ribulose bisphosphate (RuBP). This reaction produces an unstable six-carbon compound that immediately splits into two molecules of three-phosphoglycerate (3-PGA).

2. Reduction

During this stage, ATP and NADPH (generated from the light-dependent reactions) are utilized to convert 3-PGA into glyceraldehyde-3-phosphate (G3P), another three-carbon molecule. This process involves six molecules of ATP and NADPH, where ATP provides energy, and NADPH supplies electrons.

3. Regeneration

In the final stage, a majority of the G3P is used to regenerate RuBP, allowing the cycle to continue. Out of every 12 G3P molecules produced, 10 are used for regeneration while 2 are typically exported to the cytoplasm for the synthesis of carbohydrates like glucose.

Overall, the Calvin-Benson cycle is essential for plant metabolism and plays a vital role in the ecosystem by converting inorganic carbon into organic substances.


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