How does a defective LDL receptor cause hyperlipidemia?
Decreased uptake of LDL by liver causes serum levels to increase. 17. What is clathrin? A: It is an intracellular protein that helps stabilize the pit in which LDL receptors are located. The receptors are recycled. 18. What effects does cholesterol have after being absorbed by the liver in LDL? A: The absorbed cholesterol inhibits cholesterol synthesis (HMG-CoA reductase), and inhibits the synthesis of LDL receptors (to prevent further uptake). Excess cholesterol can be stored in the cell as a cholesteryl ester. 19. What are “foam” cells and how do they form? A: These are macrophages that have ingested oxidized LDL. Apparently, macrophages do not ingest normal LDL (only the oxidized form). They accumulate large amounts of cholesterol and are thought to play a major role in deposition of lipid in artery walls as seen in atherosclerosis. 20. What is the difference between hormone-sensitive lipase and lipoprotein lipase? A: HSL breaks down TAGs which are stored in adipose tissue into fatt
