Carbohydrate Metabolism

Describe the physiology and biochemistry of fat, carbohydrate and protein metabolism

Storage

Carbohydrates are stored in liver and muscle as glucose polymers known as glycogen.

  • The liver contains ~100g of glycogen
    This can maintain plasma glucose for ~24 hours.
  • Skeletal muscle cotains ~200g of glycogen
    This cannot be released into circulation, and is for use only by the muscle.

Production of glycogen is stimulated by insulin, which is released as plasma glucose levels rise following carbohydrate ingestion. When plasma glucose levels fall, the release of glucagon and adrenaline stimulates glycogenolysis.

Metabolism

Glycolysis

Glycolysis:

  • Describes the process of converting glucose into pyruvate
    This is known as the Embden-Meyerhof pathway.
  • Occurs in the cytoplasm
  • Does not consume oxygen or produce carbon dioxide
  • Produces 2 ATP
    Glycolysis allows production of ATP in anaerobic conditions.

Gluconeogenesis

Gluconeogenesis is the production of glucose from other molecules. Gluconeogenesis:

  • Requires ATP to perform
    Some organs (heart, brain) rely on glucose for ATP
  • Has many potential substrates:
    • Lactate
    • Pyruvate
    • Glycerol
    • Amino acids
    • CAC-intermediates
  • Is stimulated by glucagon
  • Is inhibited by biguanides (metformin)

References

  1. Chambers D, Huang C, Matthews G. Basic Physiology for Anaesthetists. Cambridge University Press. 2015.
Last updated 2017-09-08

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