Biochem Cholesterol and Lipoproteins

Chylomicron remnants are rapidly taken by the liver in a process that requires

ApoE

The highest phospholipids content is found in …........................

HDL

True or False: HDL increases LDL oxidation

False

Where does IDL become LDL?

In the liver, blood capillaries and the liver

True or false: Cholesterol biosynthesis takes place in the cytoplasm and smooth ER

True

3-hydroxy, 3-methylglutaryl-CoA (HMG-CoA) is not only the substrate for the rate-limiting enzyme of cholesterol synthesis, but also an intermediate in the synthesis of _______

Ketone bodies

Cholesterol metabolism is control by HMG CoA _____

reductase

Statins are the most important type of cholesterol-lowering drug, and they lower specifically LDL rather than HDL cholesterol. How do the statins lower LDL cholesterol?

By inhibiting HMG-CoA reductase, thereby preventing cholesterol synthesis and forcing the cells to obtain their cholesterol from LDL

True or false: HDL removes cholesterol from tissues

True

A 40-yo man presents severe pain in the legs upon walking. He is diagnosed with atherosclerotic plaques in the arteries of his legs. High levels of cholesterol and LDL contributed to the formation of atherosclerosis. Which lipoprotein is digested to form LDL?

IDL

Chylomicron is a type of lipoprotein that transports triglycerides from the intestine to peripheral tissues. Which of the following is an integral apolipoprotein present in a chylomicron?

Apo B48

The HDL is taken up by the hepatocytes via.................................

Scavenger receptor BI

The cholesterol serves as the precursor for the following biosynthetic pathways, EXCEPT

• Aldosterone synthesis

• Steroid hormone synthesis

• Thyroid hormone synthesis

• Bile acid synthesis

Thyroid hormone synthesis

True or false: The rate limiting enzyme of cholesterol biosynthesis is HMG CoA synthase

False

The clearance of LDL cholesterols in hepatocytes requires:

LDL receptor

True or false: Cholesterol is an important constituent of plasma membranes of animals.

True

True or false: Insulin stimulates cholesterol synthesis.

True

The class of lipoproteins that is protective against atherosclerosis is …...........................

High-density lipoproteins

Which one of the following lipoproteins is the major carrier of triacylglycerol?

• HDL and VLDL

• IDL and HDL

• chylomicron and VLDL

• LDL and HDL

chylomicron and VLDL

The clearance of LDL cholesterols in hepatocytes requires:

LDL receptor

True or false: A 23-yo female presents with low RBC count, corneal opacities and kidney insufficiency. She has been diagnosed with lecithin: cholesterol acyltransferase (LCAT) Deficiency. LCAT is involved in converting cholesterol to cholesteryl esters.

True

True or false: HMG CoA reductase is located in the smooth ER.

True

Bile acid is derived from:

cholesterol

True or false: MHG CoA reductase cause the lowering of cholesterol and LDL levels by inhibiting the rate-limiting step in cholesterol biosynthesis.

True

Which lipoprotein has the highest cholesterol:triglycerides ratio?

LDL and HDL

Excess cholesterol needs to be transported to the liver because it cannot be metabolized in most extrahepatic tissues. This 'reverse' transport of cholesterol requires a lipoprotein that is not required for other routes of cholesterol transport. This lipoprotein is______

HDL