Final answer:
Hormone-sensitive lipase (HSL) is turned on in a fasted state and is regulated by allosteric activation through the binding of hormones such as epinephrine and glucagon.
Step-by-step explanation:
In a fasted state, the HSL (hormone-sensitive lipase) is turned on. HSL is an enzyme that helps break down stored triglycerides (fat) into free fatty acids and glycerol, which can then be used as a fuel source by the body.
The regulation of HSL is allosteric, meaning it is controlled by the binding of certain molecules to allosteric sites on the enzyme. HSL is activated allosterically by the binding of certain hormones such as catecholamines (e.g., epinephrine) and glucagon. These hormones bind to specific receptors on the surface of fat cells, triggering a signaling cascade that ultimately activates HSL.