light-independent

• light-independent stage?

  hydrogen from reduced NADP and carbon dioxide is used to build organic molecules, such as glucose. ATP supplies the required energy.
• takes place in the stoma
• uses ATP and NADPH from the light dependent reaction
• does not require light
• what are the stages of the calvin cycle?

  fixation, reduction, regeneration
• fixation

  Ribuolse bisphosphate (5C) reacts with carbon dioxide (1C).

  catalysed by Ribulose bisphosphate carboxylase (RuBisCO).

  this makes 3 molecules of glycerate 3-phosphate (3C).
• reduction


  each molecule of glycerate 3-phosphate is reduced to form a 3C sugar, triose phosphate.

  uses reduced NADPH and ATP from the light dependent reactions. the NADPH provides hydrogen and the ATP provides energy.

  some of the triose phosphate is removed from the cycle and used by the plant cell to make glucose, amino acids and lipids.
• regeneration

  ribulose bisphosphate is regenerated using ATP to allow the cycle to continue.
• each turn of the calvin cycle fixes one carbon atom from carbon dioxide. this means that the cycle has to turn 6 times to produce one molecule of glucose.
• carbon dioxide enters the intercellular spaces within the spongy mesophyll of leaves by diffusion from the atmosphere.
• RuBisCO is an inefficient enzyme as it is competitively inhibited by oxygen
• in 6 turns of the cycle 12 TP molecules are formed, two of which will be removed to make the glucose molecule.
• 10 TP molecules are recycled to regenerate six RuBP molecules.