Lipid Metabolism & Physiology Flashcards

Which dietary fatty acid class is most effective at raising LDL cholesterol levels?

Answer: Trans fatty acids

Trans fatty acids both raise LDL-C and lower HDL-C, making them uniquely atherogenic compared to saturated fats which raise both LDL and HDL.

Lp(a) is formed when LDL binds covalently to which protein?

Answer: Apolipoprotein(a)

Lp(a) is formed by a disulfide bond between ApoB-100 on LDL and apolipoprotein(a), which structurally resembles plasminogen and may promote thrombosis and atherosclerosis.

Which enzyme esterifies free cholesterol within HDL particles to form cholesteryl esters?

Answer: LCAT

Lecithin-cholesterol acyltransferase (LCAT) is activated by ApoA-I and esterifies free cholesterol in HDL, trapping it in the particle core and driving cholesterol efflux from tissues.

A patient with type III hyperlipidemia (dysbetalipoproteinemia) has excess accumulation of which lipoprotein remnants?

Answer: VLDL remnants (IDL) and chylomicron remnants

Type III hyperlipidemia (familial dysbetalipoproteinemia) results from ApoE2 homozygosity, which impairs hepatic clearance of IDL and chylomicron remnants, causing equal elevations of cholesterol and triglycerides.

In the exogenous lipid pathway, chylomicrons are assembled in which cells?

Answer: Intestinal enterocytes

Chylomicrons are synthesized in intestinal enterocytes from dietary lipids and secreted into lymphatic lacteals before entering the circulation via the thoracic duct.

Which receptor mediates hepatic uptake of LDL particles through endocytosis?

Answer: LDL receptor (LDLR)

The LDL receptor (LDLR) recognizes ApoB-100 on LDL and mediates its uptake into hepatocytes via clathrin-coated pit endocytosis, where the receptor is recycled.

Omega-3 fatty acids (EPA and DHA) primarily lower which lipid parameter?

Answer: Triglycerides

High-dose omega-3 fatty acids reduce hepatic VLDL triglyceride synthesis and increase triglyceride clearance, lowering serum triglycerides by 20-50% at therapeutic doses (4 g/day).