Gluconeogenesis Flashcards
What is gluconeogenesis?
The synthesis of glucose within the body from non-carbohydrate precursors.
What are the precursors for gluconeogenesis?
- Lactate - synthesised by skeletal muscle under anaerobic conditions.
- Amino acids - derived from muscle protein by proteolysis.
- Glycerol - derived from triglycerides by lipolysis in adipose tissue.
Where does the energy for gluconeogenesis come from?
Oxidation of fatty acids released from adipose tissue.
Breakdown of body protein.
Where does gluconeogenesis occur?
Mainly in the liver, small amount in kidneys.
What are the enzymes that catalyse the 3 irreversible reactions in glycolysis?
Hexokinase, phosphofructokinase and pyruvate kinase.
What type of enzymes does gluconeogenesis require?
4 unique liver enzymes.
What needs to be produced for gluconeogensis to go forward?
Oxaloacetate in the mitochondria.
How much ATP and GTP is required for gluconeogenesis?
4ATP and 2GTP.
What does the cori cycle involve?
Lactate as a precursor for gluconeogenesis.
Describe how glucose is formed from lactate produced in muscle.
Blood transports lactate to liver where it converts lactate back to glucose (costs 6 ATP). The glucose is then released into the bloodstream.
What is the advantage of using lactate as a precursor for gluconeogenesis?
It buys time and shifts metabolic burden from muscle to other organs allowing the muscle to continue.
What are the 2 classes of amino acids and which one can be used for gluconeogenesis?
Glucogenic and ketogenic amino acids. Glucogenic.
What happens to the TCA cycle if oxaloacetate is used up in gluconeogensis?
Acetyl-CoA cannot be accepted so the TCA cycle cannot continue.
Describe the system level regulation (hormonal regulation) of gluconeogenesis.
Glucagon stimulates gluconeogenesis and inhibits glycolysis. Insulin inhibits gluconeogenesis and stimulates glycolysis.
On the cellular level, high concentrations of what will stimulate glycolysis and inhibit gluconeogenesis?
AMP or ADP, fructose-2,6-biphosphate (high in fed state, low in starved state), citrate, alanine and acetyl-CoA (intermediates of TCA cycle).
