Chapter 26. The Biosynthesis of Membrane Lipids and Steroids

Question 1

A sphingosine with a long-chain acyl group attached to the amino group.

Answer 1

Ceramide

Question 2

the highly-regulated enzyme that catalyzes the committed step in cholesterol synthesis the formation of mevalonate from 3-hydroxy-3-methylglutaryl CoA.

Answer 2

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

Question 3

A sphingolipid in which glucose or galactose is linked to the terminal hydroxyl group of a ceramide.

Answer 3

Cerebroside

Question 4

a ceramide, common in membranes of the nervous system, in which an oligosaccharide is linked to the ceramide by a glucose residue.

Answer 4

Ganglioside

Question 5

glycerols that have fatty acyl chains esterified to each of their hydroxyl groups; storage form of fats; also known as neutral fats or triglycerides.

Answer 5

Triacylglycerol

Question 6

an activated precursor for the synthesis of many phospholipids formed by the reaction of phosphatidate with CTP.

Answer 6

Cytidine diphosphodiacylglycerol (CDP-diacylglycerol)

Question 7

a sphingosine with a long-chain acyl group attached to the amino group.

Answer 7

(N-acyl sphingosine)

Question 8

A sterol that is an important constituent of eukaryotic membranes as well as lipoproteins; also a precursor of steroid hormones.

Answer 8

Cholesterol

Question 9

particles, consisting of a core of hydrophobic lipids surrounded by a shell of polar lipids and specific proteins, that play a role in the transport of cholesterol and triacylglycerols.

Answer 9

Lipoprotein particles

Question 10

a precursor to cholesterol as well as a large variety of other biomolecules such as vitamin K, coenzyme Q and the carotenoids. Isopentyl pyrophosphate is derived from mevalonate.

Answer 10

3-isopentenyl pyrophosphate

Question 11

polar derivatives of cholesterol that are made in the liver, stored in the gall bladder, and released into the small intestine, where they act as detergents to solubilize dietary lipids, facilitating their digestion and absorption.

Answer 11

Bile salt

Question 12

a lipoprotein that collects cholesterol released into the blood from dying cells or from membranes undergoing turnover.

Answer 12

High-density lipoprotein (HDL)

Question 13

a precursor for the synthesis of cholesterol whose formation by HMG-CoA reductase constitutes the committed step in cholesterol biosynthesis.

Answer 13

Mevalonate

Question 14

the major carrier of cholesterol in the blood; consists of a core of esterified cholesterol molecules surrounded by a shell of phospholipids, unesterified cholesterol, and apoprotein B-100; primary source of cholesterol for cells other than the liver or intestine.

Answer 14

Low-density lipoprotein (LDL)

Question 15

A family of mixed function oxygenases that add OH groups to various biochemicals, including steroid hormones. These enzymes require NADPH, O2 and cytochrome P450.

Answer 15

Cytochrome P450 monooxygenase

Question 16

diacylglycerol 3-phosphate. Phosphatidate is a precursor to triacylglycerols as well as many phospholipids.

Answer 16

Phosphatidate

Question 17

A phospholipid whose backbone is sphingosine rather than glycerol. Spingolipids are present in all eukaryotic cells, although their concentration is highest in cells of the central nervous system. They are also prominent components of lipid rafts.

Answer 17

Sphingolipid

Question 18

important constituents of membranes, composed of three components: a backbone (usually glycerol or sphingosine), two fatty acid chains, and a phosphorylated alcohol.

Answer 18

Phospholipid

Question 19

a transcription factor that binds to the sterol regulatory element of the HMG-CoA reductase gene and other genes in cholesterol metabolism to stimulate their transcription.

Answer 19

Sterol regulatory element binding protein (SREBP)

Question 20

a means of importing specific proteins into a cell by their binding to plasma membrane receptors and their subsequent endocytosis and inclusion into vesicles.

Answer 20

Receptor-mediated endocytosis

Question 21

The retrieval of cholesterol from peripheral tissues by HDL for return to the liver for excretion as bile or in the feces.

Answer 21

Reverse cholesterol transport

Question 22

hormones, such as androgen and estrogen, derived from cholesterol.

Answer 22

Steroid hormone