Lecture on Pentose Phosphate Pathway (PPP)

Importance of PPP

• Essential for synthesis reactions:
  • Neurotransmitters, lipids, cholesterol
  • Nucleotides and other biomolecules
• Crucial for free radical reactions

Entry of Glucose into the Cell

• Glucose needs transporters like GLUT2 (in liver cells)
• Glucose converted to Glucose-6-Phosphate (G6P) by Glucokinase
  • Involves ATP to ADP conversion

Glycolysis Pathway

• G6P can enter glycolysis:
  • Converts to Fructose-6-Phosphate (F6P), then Fructose-1,6-bisphosphate
  • Process involves ATP consumption and production of ATP
  • Net production: 2 ATP (gross: 4 ATP)

Pentose Phosphate Pathway (PPP)

1. Oxidative Phase:

   • Conversion of G6P to 6-Phosphogluconolactone (via Glucose-6-Phosphate Dehydrogenase)
   • 6-Phosphogluconolactone converts to 6-Phosphogluconate (via Lactonase)
   • Converts to Ribulose-5-Phosphate; generates NADPH, CO2

2. Non-Oxidative Phase:

   • Ribulose-5-Phosphate conversion to Ribose-5-Phosphate and Xylulose-5-Phosphate via isomerization
   • Carbon shuffling reactions:
     • Involves enzymes like Transketolase, Transaldolase
     • Produces intermediates such as Glyceraldehyde-3-Phosphate, Fructose-6-Phosphate

Functions of Key Molecules

• NADPH:

  • Strong reducing agent, used in biosynthetic pathways:
    • Fatty acid and cholesterol synthesis
    • Nucleotide, neurotransmitter synthesis
  • Aids antioxidant enzymes

• Ribose-5-Phosphate:

  • Synthesis of nucleotides, DNA, RNA
  • Precursor for ATP, NAD+, FAD, Coenzyme A

Significance of PPP

• Can produce NADPH and Ribose-5-Phosphate independently
• Participates in gluconeogenesis and glycolysis based on cellular demands
• Potential issues, such as enzyme deficiencies, can lead to conditions like hemolytic anemia

Upcoming Discussions

• Detailed look into regulation of PPP
• Exploring the role of PPP in free radical reactions and its antioxidant functions