Disorders of Lipid Metabolism Quiz

Study Notes

Lipids are organic compounds that are poorly soluble in water but miscible in organic solvents.
Lipids play a critical role in biological life, being structural components in cells and involved in metabolic and hormonal pathways.

Fatty acids are straight-chain carbon compounds of varying lengths.
Fatty acids can be saturated (no double bonds), monounsaturated (one double bond), or polyunsaturated (more than one double bond).
Fatty acids can esterify with glycerol to form triglycerides or be non-esterified (NEFAs) or free.

Triglycerides are transported from the intestine to various tissues, including the liver and adipose tissue, as lipoproteins.
Following hydrolysis, fatty acids are taken up, re-esterified and stored as triglycerides.
Plasma triglyceride concentrations rise after a meal, unlike that of plasma cholesterol.

Phospholipids are complex lipids, similar in structure to triglycerides but containing phosphate and a nitrogenous base in place of one of the fatty acids.

Cholesterol is a steroid alcohol found exclusively in animals and present in virtually all cells and body fluids.
Cholesterol is a precursor of numerous physiologically important steroids, including bile acids and steroid hormones.

Lipoproteins are soluble protein complexes that transport lipids in body fluids.
Lipoproteins can be classified into five main groups: chylomicrons, VLDLs, IDLs, LDLs, and HDLs.

Chylomicrons: largest and least dense lipoproteins, transporting exogenous lipid from the intestine to cells.
VLDLs: transporting endogenous lipid from the liver to cells.
IDLs: transient and formed during the conversion of VLDL to LDL.
LDLs: formed from VLDLs and carrying cholesterol to cells.
HDLs: densest lipoproteins, involved in the transport of cholesterol from cells back to the liver (reverse cholesterol transport).

Hyperlipoproteinemia: elevation of one or more lipoprotein fractions in the plasma.
According to Frederickson's classification, there are 5 types of hyperlipoproteinemia:
- Type-1: lipoprotein lipase enzyme deficiency, increased plasma chylomicron and VLDL levels.
- Type-2a: LDL receptor deficiency, increased plasma LDL cholesterol.
- Type-2b: overproduction of apo B, increased plasma LDL and VLDL.
- Type-3: increased IDL.
- Type-4: increased VLDL.
- Type-5: increased VLDL and chylomicron.

Hypolipoproteinemia: condition of decreased lipoprotein fraction.
Types of hypolipoproteinemia:
- Familial hypolipoproteinemia: failure in the synthesis of apo B lipoproteins, decreased LDL level.
- Abetalipoproteinemia: absence of Apo B100, LDL fraction is completely absent.
- Familial α-lipoprotein deficiency.