Question

Explain Calvin cycle.

Answer 1

Calvin cycle is the set of chemical reactions that take place in chloroplasts during photosynthesis. The cycle is light-independent because it takes place after the energy has been captured from sunlight. The steps involved in the Calvin cycle are as follows -

• A five-carbon carbon molecule called Ribulose-5-phosphate which takes up one molecule of carbon dioxide and forms a six-carbon molecule (ribulose-1,5-bisphosphate).
  
• The enzyme RuBisCO with the energy of ATP and NADPH molecules breaks the six-carbon molecule into two equal parts.
  
• One 3-carbon molecule leaves the cycle and becomes sugar. Another 3-carbon molecule moves on to the next step and undergoes reduction producing Glyceraldehyde-3-phosphate.
• Using ATP and NADPH, the three carbon molecule (Glyceraldehyde-3-phosphate) is changed into a five-carbon molecule (Ribulose-5-phosphate) and the cycle is repeated again.