Lipoproteins: Complex molecules with a nonpolar core (triglycerol, cholesterol esters) surrounded by a surface layer of phospholipids, cholesterol, and apolipoproteins (70% of HDL, 1% of chylomicrons).

Classes of Lipoproteins:

• Chylomicrons:

• Largest and least dense lipoproteins.

• Derived from intestinal absorption of triglycerides.

• High proportion of triglycerides.

• Apolipoproteins: apo B48, apo E, apo C2.

• Very Low Density Lipoproteins (VLDL):

• Transport triglycerides from liver to muscle/adipose tissue.

• Apolipoproteins: apo B100, apo C1, C2, C3, and E.

• Convert to intermediate density lipoproteins (IDL) after losing triglycerides.

• Low Density Lipoprotein (LDL):

• Final stage of VLDL catabolism.

• Carries cholesterol to tissues (bad cholesterol).

• Apolipoprotein: apo B100 (4,536 amino acids; 550,000 Da).

• High Density Lipoprotein (HDL):

• Originates from liver/small intestine (good cholesterol).

• Absorbs and returns excess cholesterol to liver for excretion.

• Apolipoprotein: apo A1.

Comparison of Lipoprotein Densities:

• Chylomicrons: Density < 1.006, contains 85% triglycerides.

• VLDL: Density 0.95 - 1.006, contains 50% triglycerides.

• LDL: Density 1.006 - 1.063, contains 37% cholesterol esters and 10% triglycerides.

• HDL: Density 1.063 - 1.21, contains highest protein (55%) and lowest triglycerides (4%).

Key Takeaways:

• Chylomicrons have the highest triglycerides, while HDL has the highest protein content.

• Understanding lipoprotein composition and function is crucial for cardiovascular health.