Table 2. Physical and biological features and functions of lipoproteins.

Category	Density (g/mL)	Diameter (nm)	Main lipid components (%)					Apoliprotein		Main source	Function
			TG	Cholesteryl- ester	Phospho- lipid	Cholesterol		Main	Other
CM: chylomicron; HDL: high-density lipoprotein; IDL: intermediate-density lipoprotein; LDL: low-density lipoprotein; Lp(a): lipoprotein (a); VLDL: very low-density lipoprotein.
CM	< 0.950	80–100	90–95	2–4	2–6	1		B48	A1, A2, A4, A5	Synthesized by the small intestine	Transport of TG and cholesterol from food from the small intestine to other tissues.
VLDL	0.950–1.006	30–80	50–65	8–14	12–16	4–7		B100	A1, C2, C3, E, A5	Synthesized by the liver	Transport of endogenous TG to peripheral tissues and release of free fatty acids after hydrolysis by lipase
IDL	1.006–1.019	25–30	25–40	20–35	16–24	7–11		B100	C2, C3, E	TG in VLDL is formed after hydrolysis by lipase	LDL precursor, partially metabolized by the liver
LDL	1.019–1.063	20–25	4–6	34–35	22–26	6–15		B100		TG in VLDL and IDL is formed after hydrolysis by lipase	The main carrier of cholesterol, mediated by LDL receptors and taken up and utilized by peripheral tissues
HDL	1.063–1.210	8–13	7	10–20	55	5		A1	A2, C3, E, M	Mainly synthesized by the liver and small intestine	Facilitates cholesterol removal from peripheral tissues and transports cholesterol to the liver or other tissues for redistribution
Lp (a)	1.055–1.085	25–30	4–8	35–46	17–24	6–9		Apo(a)	B100	Complex formation of Apo(a) with LDL via disulfide bonds in the liver or extra-hepatically	Function has not been fully understood yet.