GENBIO CALVIN CYCLE II

CYCLE ITSELF

Carboxylation phase

The first phase of the Calvin Cycle where carbon dioxide is attached to ribulose-1,5-bisphosphate (RuBP).

Ribulose-1,5-bisphosphate (RuBP)

A five-carbon sugar that accepts carbon dioxide during carbon fixation.

RuBisCO

The enzyme that catalyzes the attachment of CO₂ to RuBP during carboxylation.

Result of carboxylation

An unstable six-carbon compound that immediately splits into two molecules of 3-phosphoglycerate (3-PGA).

3-phosphoglycerate (3-PGA)

A three-carbon compound formed directly after carbon fixation.

Reduction phase

The phase of the Calvin Cycle where ATP and NADPH are used to convert 3-PGA into G3P.

Phosphoglycerate kinase

A kinase enzyme that transfers a phosphate group from ATP to 3-phosphoglycerate.

Function of kinase enzymes

Transfer of phosphate groups using ATP.

ATP usage in reduction

ATP phosphorylates 3-PGA to form 1,3-bisphosphoglycerate.

1,3-bisphosphoglycerate

An intermediate formed after phosphorylation of 3-PGA.

Glyceraldehyde-3-phosphate dehydrogenase

The enzyme that reduces 1,3-bisphosphoglycerate using NADPH.

Role of NADPH in reduction

Donates high-energy electrons and hydrogen ions to reduce compounds.

Glyceraldehyde-3-phosphate (G3P)

The three-carbon sugar produced during the reduction phase.

Fate of G3P

One G3P leaves the cycle to form sugars while the remaining G3Ps enter regeneration.

Regeneration phase

The phase where G3P molecules are rearranged to regenerate RuBP.

Triose phosphate isomerase

Converts dihydroxyacetone phosphate (DHAP) and G3P into each other.

Dihydroxyacetone phosphate (DHAP)

A three-carbon sugar that can be converted into G3P.

Aldolase

An enzyme that joins three-carbon sugars to form six-carbon sugars.

Function of aldolase

Formation of glucose-related compounds by combining carbon chains.

Fructose-1,6-bisphosphate

A six-carbon sugar formed by aldolase activity.

Fructose bisphosphatase

A bisphosphatase enzyme that removes a phosphate group using water.

Function of bisphosphatase enzymes

Transfer or removal of phosphate groups using H₂O.

Fructose-6-phosphate

A six-carbon sugar that can be converted into glucose or used in regeneration.

Transketolase

An enzyme that transfers two-carbon units between sugar molecules.

Meaning of transketolase

Trans means transfer.

Role of transketolase in regeneration

Transfers two-carbon fragments to rearrange carbon skeletons.

Erythrose-4-phosphate

A four-carbon sugar formed during regeneration.

Sedoheptulose-1,7-bisphosphate

A seven-carbon sugar intermediate in regeneration.

Sedoheptulose bisphosphatase

Removes a phosphate group from sedoheptulose-1,7-bisphosphate using water.

Sedoheptulose-7-phosphate

A seven-carbon sugar formed after dephosphorylation.

Phosphopentose epimerase

An enzyme that changes the configuration of a sugar molecule.

Function of epimerase enzymes

Inverts the configuration of the third carbon atom.

Ribose-5-phosphate

A five-carbon sugar involved in RuBP regeneration.

Xylulose-5-phosphate

A five-carbon sugar formed during carbon rearrangement.

Ribulose-5-phosphate

A five-carbon sugar precursor to RuBP.

Phosphoribulose kinase

A kinase enzyme that converts ribulose-5-phosphate into RuBP using ATP.

Function of phosphoribulose kinase

Transfers a phosphate group using ATP to regenerate RuBP.

ATP use in regeneration

ATP is required to regenerate ribulose-1,5-bisphosphate.

Importance of regeneration

Allows the Calvin Cycle to continue fixing carbon dioxide.

Connection of Calvin Cycle to glucose formation

G3P molecules are used to synthesize glucose, starch, sucrose, and cellulose.

Final purpose of the Calvin Cycle

To produce carbohydrates that support plant cells, tissues, and organs.