Describe lipoprotein types and their roles in lipid transport.

Lipoproteins transport hydrophobic lipids in blood. Classes by density: Chylomicrons (lowest density) transport dietary lipids from intestine to tissues; lipoprotein lipase releases fatty acids for uptake. VLDL (very low density) exports liver-synthesized triglycerides to peripheral tissues. As triglycerides are removed, VLDL becomes IDL then LDL (low density), which delivers cholesterol to tissues via LDL receptor. HDL (high density) performs reverse cholesterol transport, collecting cholesterol from peripheral tissues for return to liver. Each has characteristic apolipoprotein composition affecting metabolism. Elevated LDL and low HDL are cardiovascular risk factors; statins lower LDL by increasing hepatic LDL receptor expression.