key term - Glyceraldehyde-3-phosphate

Definition

Glyceraldehyde-3-phosphate (G3P) is a three-carbon sugar phosphate that plays a crucial role in the Calvin cycle, the light-independent reactions of photosynthesis. It serves as an important intermediate and is directly involved in the synthesis of glucose and other carbohydrates. G3P is generated during the reduction phase of the Calvin cycle and can be utilized for energy production or as a building block for larger organic molecules.

5 Must Know Facts For Your Next Test

1. G3P is produced from 3-phosphoglycerate (3-PGA) through a series of enzymatic reactions in the Calvin cycle, specifically during the reduction phase.
2. For every three molecules of CO2 that enter the Calvin cycle, one molecule of G3P is generated, which can then be used to form glucose or regenerate ribulose bisphosphate (RuBP).
3. G3P can be converted into various carbohydrates such as glucose, starch, and sucrose, serving as a vital precursor for plant energy storage and structural components.
4. In addition to its role in carbohydrate synthesis, G3P can also be involved in the synthesis of lipids and amino acids, making it a key metabolite in cellular metabolism.
5. The conversion of G3P into glucose requires an additional investment of ATP and NADPH after its production in the Calvin cycle.

Review Questions

• How does glyceraldehyde-3-phosphate function within the Calvin cycle to contribute to carbohydrate synthesis?
  • Glyceraldehyde-3-phosphate (G3P) is produced during the reduction phase of the Calvin cycle when 3-phosphoglycerate is converted using ATP and NADPH. For every three molecules of carbon dioxide that enter the cycle, one molecule of G3P is generated. This G3P can either be used immediately to synthesize glucose or other carbohydrates or be recycled to regenerate ribulose bisphosphate (RuBP), ensuring continuous operation of the Calvin cycle.
• Discuss the importance of NADPH in the formation of glyceraldehyde-3-phosphate during the Calvin cycle.
  • NADPH is essential in the Calvin cycle as it provides the reducing power needed to convert 3-phosphoglycerate into glyceraldehyde-3-phosphate (G3P). The reduction process involves transferring electrons from NADPH to 3-PGA, facilitated by enzymes. This transformation is critical because it not only generates G3P but also enables plants to build carbohydrates from CO2, demonstrating how NADPH links light-dependent reactions with carbon fixation.
• Evaluate the significance of glyceraldehyde-3-phosphate beyond its role in carbohydrate synthesis within plant metabolism.
  • Glyceraldehyde-3-phosphate (G3P) extends its significance beyond carbohydrate synthesis by serving as a key metabolite for producing lipids and amino acids. Since G3P can be converted into various organic compounds, it plays a central role in cellular metabolism and energy balance within plants. This versatility underscores its importance not only for immediate energy storage through carbohydrates but also for overall plant growth and development through other biosynthetic pathways.

Related terms

Calvin Cycle:

A series of biochemical reactions that take place in the stroma of chloroplasts during photosynthesis, converting carbon dioxide into glucose using ATP and NADPH.

RuBisCO: Ribulose bisphosphate carboxylase/oxygenase, an enzyme that catalyzes the first step of the Calvin cycle by fixing carbon dioxide to ribulose bisphosphate.

NADPH:

Nicotinamide adenine dinucleotide phosphate, an electron carrier that provides reducing power in the Calvin cycle to convert 3-phosphoglycerate into glyceraldehyde-3-phosphate.