Lipids as an energy source
The utilization of lipids for energy production takes place in three basic phases:
- Lipid mobilization - hydrolysis of TAG to MK and glycerol and their transport blood.
- Activation of MK in the cytosol and their transport into the matrix mitochondria.
- β-oxidation - breaking down MK into acetyl~CoA, which enters the Krebs cycle, or ketone bodies are formed from it.
Lipid mobilization – lipolysis
The mobilization of stored lipids is enzymatically ensured by hormone-sensitive lipase' (HSL). It catalyzes the reaction:
- TAG → 3 MK + glycerol
The released fatty acids bind to serum albumin, which transports them to their destination (e.g. the liver). Glycerol is transported freely dissolved in plasma.
Regulation of lipolysis
As the name suggests, the enzyme is under strict hormonal control. Its activity is stimulated by the ``phosphorylation of its molecule. Insulin as an anabolic hormone causes its inhibition, counterregulatory hormones (glucagon, catecholamines) or thyroid hormones on the contrary activate it.
