Examples of ribulose in the following topics:
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- The carbon dioxide is combined with ribulose 1,5-bisphosphate to form two 3-phosphoglycerate molecules (3-PG).
- The enzyme that catalyzes this specific reaction is ribulose bisphosphate carboxylase (RuBisCO).
- RuBisCO is only active during the day as its substrate, ribulose 1,5-bisphosphate, is not generated in the dark.
- This phase is characterized by the conversion of G3P, which was produced in earlier phase, back to ribulose 1,5-bisphosphate.
- Outline the three major phases of the Calvin cycle: carbon fixation, reduction, and regeneration of ribulose
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- The first is the oxidative phase in which glucose-6-phosphate is converted to ribulose-5-phosphate.
- Glucose 6-phosphate + 2 NADP+ + H2O → ribulose-5-phosphate + 2 NADPH + 2 H+ + CO2
- Depending on the body's state, ribulose-5-phosphate can reversibly isomerize to ribose-5-phosphate.
- Ribulose-5-phosphate can alternatively undergo a series of isomerizations as well as transaldolations and transketolations that result in the production of other pentose phosphates including fructose-6-phosphate, erythrose-4-phosphate, and glyceraldehyde-3-phosphate (both intermediates in glycolysis).
- It produces ribulose-5-phosphate, used in the synthesis of nucleotides.
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- The Calvin cycle can be divided into three major phases which include: Phase 1: carbon fixation; Phase 2: reduction; and Phase 3: regeneration of ribulose .
- However, additional GAP molecules that are formed will be converted to ribulose-1,5-bisphosphate (RuBP), which is responsible for the conversion of CO2 to 3-PGA in phase 1, via numerous steps.
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- These compartments are thought to concentrate carbon dioxide to overcome the inefficiency of RuBisCo (ribulose bisphosphate carboxylase/oxygenase) - the predominant enzyme in carbon fixation and the rate limiting enzyme in the Calvin cycle.