Lipid Metabolism Flashcards
The rate limiting step in cholesterol synthesis involves
enzyme 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase
(Enzyme inhibited in Statins)
Five types of Lipoproteins (listed in order of % of TG)
Chylomicrons Very low density lipoprotein (VLDL) Intermediate density lipoprotein (IDL) Low density lipoprotein (LDL) The main carrier of cholesterol High density lipoprotein (HDL)
LDL (“Bad” Cholesterol)
The main carrier of cholesterol
LDL is removed from the circulation by either LDL receptors (70%) on hepatocytes or by non-receptor mechanisms involving scavenger cells such as macrophages
HDL (“Good” Cholesterol)
Synthesized in the liver
Participates in the reverse transport of cholesterol, that is, carrying cholesterol from the peripheral tissues back to the liver
Atherosclerosis
begins with accumulation of lipoproteins (primarily LDL) within the inner layer of the arterial wall
Lipoprotein
phospholipid + protein complex circulating in blood
Apoprotein
provide interface between lipids and aqueous environment
regulate lipid transport
regulate lipoprotein metabolism
Chylomicrons
Exogenous transport pathway
Carry TG, dietary fat and cholesterol from the gut to the liver
VLDL
Endogenous transport pathway
Main carrier of TG (also cholesterol and cholesterol esters) from the liver to peripheral tissues
HDL
Carries cholesterol from peripheral tissues back to liver
Inverse correlation with coronary heart disease risk
LDL
Main carrier of cholesterol from liver to peripheral tissues
Linked to coronary atherosclerosis
Elevation result from excess production or defective clearance and utilization of cholesterol
Ketosis
Ketosis is a result of the liver converting fat into fatty acids and ketone bodies (which can be used for energy as an alternative to glucose)
Excess ketone bodies will decarboxylate into acetone:
Starvation
When large amounts of fat are eaten in the absence of carbohydrate (Such as low carb diets)
