Integration of Metabolic Pathways

Overview

• Series of 3 videos.
• Focus: Interconnection and interaction of metabolic pathways.
• Focus on the substrates and their interconnections, not on ATP or NADH.

Carbohydrates

Storage and Breakdown

• Storage: Stored as glycogen in skeletal muscles, cardiac muscle, and liver.
  • Polysaccharide: Glycogen
• Glycogenolysis: Breakdown of glycogen to glucose.
  • Occurs in the fasting state.
• Glycogenesis: Conversion of glucose to glycogen.
  • Occurs in the fed state.

Glycolysis

• Process: Breakdown of glucose into pyruvate.
  • Key Intermediate: Fructose 1,6-bisphosphate → DHAP (Dihydroxyacetone phosphate) and G3P (Glyceraldehyde 3-phosphate).
  • End Product: 2 Pyruvate molecules.
• Transition Stage: Conversion of pyruvate into acetyl-CoA.
  • Produces CO2.

Krebs Cycle

• Process: Acetyl-CoA enters the Krebs cycle, producing intermediates.
  • Generates NADH and FADH2.

Electron Transport Chain (ETC)

• Role: NADH and FADH2 from the Krebs cycle go to the ETC.
  • Purpose: Produce ATP (energy for cells).

Pentose Phosphate Pathway (PPP)

• Role: Conversion of glucose to ribose-5-phosphate.
  • Important for nucleotide and neurotransmitter synthesis.
  • Produces NADPH.

Summary of Pathways

• Glycogenesis: Glucose → Glycogen.
• Glycogenolysis: Glycogen → Glucose.
• PPP: Glucose → Ribose-5-phosphate.
• Glycolysis: Glucose → 2 Pyruvate.
• Transition Stage: Pyruvate → Acetyl-CoA.
• Krebs Cycle: Acetyl-CoA → NADH, FADH2 (and some ATP).
• ETC: NADH, FADH2 → ATP.

Conclusion

• Next video will cover the integration of fats into these pathways.