Blood Glucose Homeostasis and Gluconeogenesis

Key Concepts

• Blood Glucose Range:

  • Maintained within 60-150 mg/dL.
  • Vital for tissues like the brain, eyes, kidneys, and red blood cells.

• Cellular Respiration Steps:

  • Glycolysis: Breakdown of glucose.
  • Krebs Cycle: Further oxidation of glucose.
  • Electron Transfer Chain: Produces bulk ATP.

Regulation of Blood Glucose

• Fed State:

  • Post-meal state.
  • GI tract breaks down food to glucose, contributing to blood glucose levels.

• Fasted State:

  • No food intake.
  • Glycogenolysis: Breakdown of glycogen (stored in liver) into glucose.
    • Glycogen stores last 10-18 hours.
  • Gluconeogenesis: Formation of new glucose from non-carbohydrate sources like amino acids and lactate.

Gluconeogenesis

• Overview:

  • Creation of new glucose.
  • Uses precursors like amino acids and lactate.
  • Maintains blood glucose and ATP supply when glycogen stores are depleted.

• Comparison with Glycolysis:

  • Almost the reverse of glycolysis.
  • Starts with pyruvate and produces glucose.
  • Reverses most reactions except three irreversible steps.

Irreversible Steps in Glycolysis

• Key Points:

  • Three steps have negative delta G (Gibbs free energy).
  • Irreversible under physiological conditions.
  • Body uses alternative pathways for these steps during gluconeogenesis.

• Three Irreversible Reactions:

  • Conversion involving glucose to glucose-6-phosphate.
  • Intermediate step.
  • Final step producing pyruvate.

Takeaways

• Glucose regulation is crucial for body function.
• Knowledge of glycolysis and gluconeogenesis pathways aids in understanding metabolic processes.