Metabolic Pathway Integration Overview

Series Objective

• Understand how metabolic pathways are interconnected and work together.
• Focus mainly on substrates of the pathways and their interconnections.
• Series consists of three videos.

Carbohydrate Metabolism

Storage of Carbohydrates

• Stored primarily as glycogen in:
  • Skeletal muscles
  • Cardiac muscle
  • Liver
• Glycogen is the storage form of glucose.

Glycogen Metabolism

• Glycogenolysis
  • Conversion: Glycogen → Glucose
  • Occurs during fasting state.
• Glycogenesis
  • Conversion: Glucose → Glycogen
  • Occurs during fed state.

Glycolysis

• Breakdown of glucose into two pyruvate molecules.
• Key Steps:
  • Fructose 1,6-bisphosphate (F1,6BP) splits into:
    • Dihydroxyacetone phosphate (DHAP)
    • Glyceraldehyde 3-phosphate (GA3P)
  • Conversion: GA3P → Pyruvate
• Pathway: Glucose → Pyruvate is glycolysis.

Pyruvate Conversion

• Transition Stage
  • Conversion: Pyruvate → Acetyl CoA
  • Pyruvate (3-carbon) loses CO₂ to form Acetyl CoA (2-carbon).

Krebs Cycle

• Acetyl CoA enters Krebs Cycle.
• Generates intermediates, NADH, FADH₂.
• Outcome: Transfer electrons to Electron Transport Chain.

Electron Transport Chain

• Utilizes NADH and FADH₂ to produce ATP.
• ATP is critical for cellular energy processes.

Pentose Phosphate Pathway

• Conversion: Glucose → Ribose 5-phosphate
• Important for nucleotide and neurotransmitter synthesis.
• Generates NADPH.

Summary of Carbohydrate Pathways

• Glycogenesis: Glucose to Glycogen
• Glycogenolysis: Glycogen to Glucose
• Pentose Phosphate Pathway: Glucose to Ribose 5-phosphate
• Glycolysis: Glucose to Pyruvate
• Transition Stage: Pyruvate to Acetyl CoA
• Krebs Cycle: Acetyl CoA processing to generate ATP
• Electron Transport Chain: Large ATP generation

Next Steps

• Next video will cover fat metabolism integration into these pathways.

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End of Part 1 on Carbohydrate Metabolism. Stay tuned for Part 2 on Fat Metabolism.