Classify lipoproteins and explain their functions.

1. 1 · Open in two lines. Lipoproteins are particles that carry fats, which do not mix with water, through the blood. Each has a fat core and a coat of phospholipids, cholesterol and apoproteins.
2. 2 · Draw the structure. [Diagram: lipoprotein ball with a core of triglycerides and cholesterol esters, a shell of phospholipids, free cholesterol and apoproteins; beside it, the five classes in order of density]
3. 3 · Classification.
   • By density (ultracentrifugation): chylomicrons, VLDL, IDL, LDL, HDL, lightest to densest.
   • By electrophoresis: chylomicrons stay at the origin; pre-β (VLDL), β (LDL), α (HDL).
4. 4 · Functions of each.
   • Chylomicrons: dietary fat from intestine to tissues.
   • VLDL: liver-made triglycerides to tissues.
   • IDL: short-lived; changes to LDL.
   • LDL: cholesterol to tissues.
   • HDL: cholesterol back to the liver (reverse cholesterol transport).
5. 5 · Apoproteins. B-48 (chylomicrons), B-100 (VLDL, LDL; binds the LDL receptor), C-II (activates lipoprotein lipase), E (remnant uptake), A-I (HDL; activates LCAT).
6. 6 · Significance. High LDL leads to atherosclerosis and heart disease; high HDL protects. Lipid profiles use these values to judge heart risk.
7. 7 · Nutrition link. Cut saturated and trans fats, eat soluble fibre, choose mixed oils and exercise regularly.
8. 8 · Close in one line. Sum up lipoproteins as the blood's fat-delivery system, with LDL and HDL as the key heart-health markers.

Scoring tip: The table carries most of the marks. Add the density order as an arrow and one line on atherosclerosis.