3-PGA

Definition

3-Phosphoglycerate (3-PGA) is a three-carbon molecule formed in the Calvin cycle during photosynthesis. It is the first stable product of carbon fixation in the C3 pathway.

5 Must Know Facts For Your Next Test

1. 3-PGA is produced from ribulose-1,5-bisphosphate (RuBP) and CO2 through the action of the enzyme RuBisCO.
2. It is a key intermediate in the Calvin cycle and is subsequently converted into glyceraldehyde-3-phosphate (G3P).
3. The formation of 3-PGA marks the beginning of the energy-consuming reactions that eventually produce glucose.
4. Each molecule of 3-PGA contains one phosphate group and three carbon atoms.
5. ATP and NADPH generated in the light-dependent reactions are used to convert 3-PGA into G3P.

Review Questions

• What enzyme catalyzes the formation of 3-PGA in photosynthesis?
• How many carbon atoms does a molecule of 3-PGA contain?
• What role do ATP and NADPH play in relation to 3-PGA?

Related terms

Ribulose-1,5-bisphosphate (RuBP): A five-carbon sugar that reacts with CO2 to form two molecules of 3-PGA in the Calvin cycle.

Glyceraldehyde-3-phosphate (G3P): A three-carbon molecule formed from the reduction of 3-PGA; it can be used to synthesize glucose.

RuBisCO:

An enzyme that catalyzes the carboxylation of RuBP, leading to the production of two molecules of 3-PGA.