Deck 26: Biosynthesis of Membrane Lipids and Steroids

Question 1

In the biosynthesis of sphingosine,the condensation of palmitoyl CoA and serine requires the coenzyme ____________________.

Answer 1

PLP,pyridoxal phosphate

Question 2

The synthesis of ____________________ is the committed step in cholesterol biosynthesis.

Answer 2

mevalonate

Question 3

______________________ is the 30-carbon precursor of cholesterol.

Answer 3

Squalene

Question 4

______________________ is the major carrier of cholesterol esters in the blood.

Question 5

Which of the following metabolites is the source of all carbons for cholesterol?

A) glucose
B) pyruvate
C) succinyl CoA
D) oxaloacetate
E) acetyl CoA

Question 6

Vitamin D₃ is converted into ______________________,which is an active hormone that functions as a transcription factor.

Question 7

Which of the following is the immediate product of HMG-CoA reductase in the cholesterol synthesis pathway?

A) isopentenyl pyrophosphate
B) mevalonate
C) squalene
D) farnesyl pyrophosphate
E) acetoacetyl CoA

Question 8

In membrane lipid biosynthesis,the nucleotide ________________ is used to activate the components of the reaction.

Question 9

Which derivative of cholesterol is the precursor of the steroid hormones?

A) aldosterone
B) progesterone
C) cortisol
D) androstenedione
E) pregnenolone

Question 10

What membrane component is produced by a base-exchange reaction with phosphatidylethanolamine?

A) phosphatidylcholine
B) phosphatidylserine
C) phosphatidylinositol
D) phosphatidic acid
E) None of the answers is correct.

Question 11

Which of the following is a principal component of the lipid-rich covering on neuronal axons?

A) vitamin A
B) phosphatidylserine
C) sphingomyelin
D) triacylglycerol
E) None of the answers is correct.

Question 12

Which of the following vitamins is a derivative of cholesterol?

A) vitamin A
B) vitamin D
C) vitamin E
D) vitamin K
E) None of the answers is correct.

Question 13

What is the primary bile salt?

A) aldosterone
B) pregnenolone
C) cortisol
D) glycocholate
E) taurocholate

Question 14

Which lipoprotein transports lipids away from the intestine?

A) chylomicron
B) very low density lipoprotein
C) low-density lipoprotein
D) high density lipoprotein
E) None of the answers is correct.

Question 15

In the biosynthesis of phosphatidates,the fatty acyl group attached to the C-2 position is usually ______________________.

Question 16

A ___________________ is composed of a fatty acid linked to sphingosine via an amide bond.

Question 17

______________________ are sphingolipids that contain an oligosaccharide unit having at least one sialic acid residue.

Question 18

What metabolite is reduced to glycerol-3-phosphate for triacylglycerol synthesis?

A) glyceraldehyde-3-phosphate
B) 3-phosphoglycerate
C) phosphoenolpyruvate
D) dihydroxyacetone phosphate
E) None of the answers is correct.

Question 19

What is the major site of triacylglycerol synthesis in mammals?

A) liver
B) adipose tissue
C) small intestine
D) kidney
E) pancreas

Question 20

In mammalian cells,phosphatidate is synthesized in the outer mitochondrial membrane and the ____________________________.

Question 21

Phosphatidate is formed from

A) glycerol 3-phosphate and two fatty acyl CoA's.
B) glycerol and two free fatty acids.
C) pyruvate and triacylglycerol.
D) glycerol and two fatty acyl CoA's.
E) glycerol 3-phosphate and diacylglycerol.

Question 22

The starting materials necessary to synthesize sphingosine are

A) palmitoyl CoA and serine.
B) acetyl CoA and glycine.
C) palmitoyl CoA and aspartate.
D) acetyl CoA and glutamine.
E) None of the answers is correct.

Question 23

Hydroxylation of cholesterol by cytochrome P450 requires

A) NADPH.
B) O₂
C) PLP.
D) thiamine.
E) NADPH and O₂.

Question 24

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

A) VLDL.
B) chylomicrons.
C) HDL.
D) LDL.
E) IDL.

Question 25

Which of the following is the common precursor for both the phosphatidyl inositols and triacylglycerols?

A) cardiolipin
B) inosinic acid
C) phosphatidate
D) CDP-diacylglycerol
E) None of the answers is correct.

Question 26

What is the role of CTP in the synthesis of a phospholipid?

Question 27

The role of lipoprotein particles is to

A) solubilize hydrophobic lipids.
B) aid in clot formation.
C) transport insoluble proteins.
D) transport free fatty acids.
E) None of the answers is correct.

Question 28

How is methionine metabolism related to the synthesis of phosphatidyl choline?

Question 29

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

A) sphingosine.
B) gangliosides.
C) dipalmitoyl phosphatidyl choline.
D) cholesterol.
E) bile salts.

Question 30

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

A) 3-hydroxy-3-methylglutaryl CoA reductase.
B) geranyltransferase.
C) HMG transferase.
D) farnesyl reductase.
E) None of the answers is correct.

Question 31

The LDL receptors on the plasma membrane are localized in coated pits that contain which of the following proteins?

A) clathrin
B) lipoprotein B-100
C) adrenodoxin
D) HMG-CoA reductase
E) SREBP, sterol regulatory element binding protein

Question 32

The energy for the conversion of provitamin D₃ to vitamin D₃ comes from

A) ATP hydrolysis.
B) NADPH oxidation.
C) thioester hydrolysis.
D) ultraviolet light from the Sun.
E) visible light from the Sun.

Question 33

What are the causes and symptoms of familial hypercholesterolemia?

Question 34

Which of the following is the major component of low-density lipoproteins?

A) sphingomyelin
B) free cholesterol
C) triacylglycerol
D) cholesteryl linoleate
E) apo B-100

Question 35

Tay-Sachs disease is caused by an inability to degrade

A) sphingosine.
B) gangliosides.
C) dipalmitoyl phosphatidyl choline.
D) ceramide.
E) None of the answers is correct.

Question 36

What is phosphatidylcholine? How is it synthesized in mammals?

Question 37

The highest concentration of sphingolipids is found in the

A) central nervous system.
B) lymph system.
C) serum.
D) adipose tissue.
E) None of the answers is correct.

Question 38

Why are phosphatidylserine,and most other phospholipids,considered classes of molecules,rather than a single molecule?

Question 39

Which of the following combines with glycine to form a major bile salt?

A) phosphatidate
B) phosphatidylethanolamine
C) glycerol
D) cholesterol
E) phosphatidylserine

Question 40

In phosphatidyl inositol,__________ and _________ usually occupy the C-1 position and the C-2 position,respectively.

A) stearic acid; cholesterol
B) stearic acid; arachidonic acid
C) palmitolyl acid; arachidonic acid
D) oleic acid; arachidonic acid
E) None of the answers is correct.

Question 41

What are the steps in LDL uptake into cells?

Question 42

How are gangliosides synthesized?

Question 43

What are bile salts?

Question 44

Describe the various ways that 3-hydroxy-3-methylglutaryl CoA reductase is regulated,including both gene expression and enzyme regulation.

Question 45

Describe cholesterol synthesis in three major steps.

Question 46

What is the role of phosphatidyl choline in the synthesis of sphingomyelin?

Question 47

How do blood levels of lipoproteins serve diagnostic purposes?

Question 48

The first step in vitamin D synthesis is unusual.What is it?

Question 49

What is the role of cytochrome P450 monooxygenases in steroid biosynthesis?

Question 50

List the types of lipoprotein particles,and give the primary physiological role of the lipoprotein.See Table 26.1Lipoprotein Physiological function