Quiz 16 Lipids 1

How does the number of carbon atoms change upon synthesis of cholesterol starting from mevalonate?

C6 → C5 → C10 → C15 → C30 → C27

Select all that apply. Hydroxylation of cholesterol by cytochrome P450 requires:

activated O2, NADPH.

What lipoproteins are used to transport lipids from the liver to the blood?

very low-density lipoproteins

A prominent means to reduce the risk of atherosclerosis is stimulation of:

reverse transport of cholesterol

Feedback regulation of cholesterol synthesis is mainly controlled at the step catalyzed by the enzyme:

3-hydroxy-3-methylglutaryl (HMG) CoA reductase.

A friend, who is struggling with weight gain, reads about a new miracle supplement that blocks the formation of phosphatidate, the precursor for triacylglycerols. Would taking this supplement work as a weight reduction scheme?

No, because this would also block formation of phospholipids, and cell membrane integrity would be impacted.

What reaction activates squalene prior to its cyclization to lanosterol?

oxidation of the C-2 and C-3 atoms

Which statement about bile is FALSE?

Polar and nonpolar regions of cholesterol make bile a good detergent.

The major carrier(s) of dietary fat from the intestine is/are:

chylomicrons.

In lipid metabolism, acetyl CoA is able to convert to a fatty acid and:

cholesterol.

Where are triacylglycerols synthesized?

ER of the liver cells

What lipoproteins are used to transport lipids from blood or tissues to the liver? Select all that apply.

intermediate-density lipoproteins, high-density lipoproteins, low-density lipoproteins

Your grandfather has been told he has high cholesterol and has been given one of the statins to bring it down. He asks if you can think of any reason that he should not double the dose so that it will reduce his blood cholesterol faster. What do you tell him?

No, some cholesterol synthesis is essential. Cholesterol is essential for proper functioning of cell membranes and for precursors for bile salts and steroid hormones.

Choose the CORRECT statement concerning receptor-mediated endocytosis in cholesterol metabolism.

Unesterified cholesterol is directed to the Golgi complex to be used for membrane biosynthesis.

HMG CoA is synthesized from acetyl CoA and:

acetoacetyl CoA.

What serves as an intermediate for the formation of phosphatidate?

lysophosphatidate

Tay–Sachs disease is caused by an inability to degrade:

gangliosides.

The committed step in cholesterol formation is the synthesis of:

mevalonate.

Select all that apply. The role of lipoprotein particles is to:

contain cell-targeting signals, solubilize hydrophobic lipids.

What functional group differs between phosphatidate and diacylglycerol?

phosphate

How many isoprene units does squalene contain?

6

The storage form of fatty acids is:

triacylglycerol.

What is the last common precursor for the synthesis of triacylglycerols and phospholipids?

phosphatidate

Respiratory distress syndrome is caused by a failure in the biosynthetic pathway of:

dipalmitoylphosphatidylcholine