Deck 19: Lipid Metabolism Ii: Membrane Lipids, Steroids, Isoprenoids, and Eicosanoids

Question 1

In prokaryotes, _________ is used exclusively as the precursor for phosphatidic acid while in eukaryotes, _________is one of three possible precursors.

A)diacylglycerol; glycerol-3-phosphate
B)glycerol-3-phosphate; dihydroxyacetone phosphate
C)dihydroxyacetone phosphate; glycerol-3-phosphate
D)3-phosphoglycerate; diacylglycerol
E)dihydroxyacetone phosphate; diacylglycerol

Answer 1

B

Question 2

How is the activity of HMG-CoA reductase reduced?

A)allosteric inhibition by cholesterol
B)ubiquitination in response to sterol accumulation resulting in proteolysis
C)serine phosphorylation by an insulin-activated protein kinase
D)tyrosine phosphorylation by AMPK
E)none of the above

Answer 2

B

Question 3

Which of the following is used to activate phosphatidic acid for conversion to various phospholipids?

A)ATP
B)UTP
C)CTP
D)GTP
E)TTP

Answer 3

C

Question 4

Which of the following is accomplished in one enzyme catalyzed reaction?

A)progesterone to androstenedione
B)17-hydroxyprogesterone to cortisol
C)progesterone to aldosterone
D)androstenedione to testosterone
E)androstenedione to estradiol

Question 5

Phospholipids are synthesized in the ___________, then transferred to the ____________ via transport vesicles.

A)smooth endoplasmic reticulum; Golgi complex
B)rough endoplasmic reticulum; smooth endoplasmic reticulum
C)smooth endoplasmic reticulum; lysosome
D)Golgi complex; smooth endoplasmic reticulum
E)Golgi complex; cell membrane

Question 6

The enzyme PGH synthase contains two different functionalities, a __________ that uses two molecules of oxygen as substrates and __________ which performs a 2 electron reduction.

A)cyclooxygenase; peroxidase
B)cyclooxygenase; reductase
C)dioxygenase; peroxidase
D)dioxygenase; reductase
E)lipoxygenase; peroxidase

Question 7

What is the term for the molecule shown below?

A)platelet-activating factor
B)1-alkyl-2-acetylglcerophosphoethanolamine
C)serine plasmologen
D)choline plasmologen
E)ethanolamine plasmologen

Question 8

Tay-Sachs disease is caused by a deficiency of __________ which results in an accumulation of ___________.

A)sphingomyelinase; sphingomyelin
B)ceramidase; ceramide
C) $\alpha$ -galactosidase A; GM₁ ganglioside
D)lysosomal N-acetylhexosaminidase A; GM₂ ganglioside
E) $\beta$ -glucosidase; glucosylceramide

Question 9

Which of the following forms of vitamin A is covalently attached to a lysine residue of the protein opsin to form the complex called rhodopsin?

A)all-trans-retinal
B)11-cis-retinal
C)all-trans-retinoic acid
D)all-trans-retinol
E) $\beta$ -carotene

Question 10

The synthesis of 1 molecule of cholesterol requires _____ molecules of isopentenyl pyrophosphate, with each molecule of isopentenyl pyrophosphate requiring _____ molecules of acetyl-CoA.

A)4; 2
B)5; 2
C)6; 2
D)5; 3
E)6; 3

Question 11

Which of the following correctly identifies the order of carbocations found in the mechanism of squalene synthase?

A)tertiary carbocation; allylic carbocation; tertiary cyclopropylcarbinyl carbocation
B)tertiary carbocation; tertiary cyclopropylcarbinyl carbocation; allylic carbocation
C)allylic carbocation; tertiary cyclopropylcarbinyl carbocation; tertiary carbocation
D)allylic carbocation; tertiary carbocation; tertiary cyclopropylcarbinyl carbocation
E)tertiary cyclopropylcarbinyl carbocation ; allylic carbocation; tertiary carbocation

Question 12

Which of the following phospholipids is produced in eukaryotes but not prokaryotes?

A)phosphatidylglycerol
B)phosphatidylserine
C)phosphatidylethanolamine
D)phosphatidylinositol
E)none of the above

Question 13

Which of the following is the regulatory step in cholesterol synthesis?

A)HMG-CoA synthase
B)HMG-CoA lyase
C)HMG-CoA reductase
D)squalene synthase
E)squalene epoxidase

Question 14

7-dehydrocholesterol reacts with _________ to produce cholecalciferol (vitamin D₃)

A)UV light
B)visible light
C)NADPH
D)NAD⁺
E)none of the above

Question 15

Which of the following explains why the bile acids are much better suited than cholesterol for use as emulsification agents for fats?

A)cholesterol is oxidized to form the more polar molecule 7-hydroxycholesterol in route to formation of the bile acids
B)while cholesterol contains a hydroxyl group as its sole hydrophilic functionality, cholic acid contains 3 hydroxyl groups and a carboxylic acid
C)cholate is conjugated with glycine to make glycocholate
D)cholate is conjugated with taurine to make taurocholate
E)all of the above

Question 16

Which of the following amino acids is critical for choline and phosphatidylcholine synthesis?

A)serine
B) $\beta$ -alanine
C)homocysteine
D)methionine
E)homoserine

Question 17

Squalene epoxidase is an example of a mixed function oxidase, meaning that it uses both _______ and _______ as substrates.

A)ATP; NADPH
B)ATP; O₂
C)NAD⁺; NADPH
D)O₂; NAD⁺
E)O₂; NADPH

Question 18

The biosynthesis of cardiolipin involves the reaction of phosphatidylglycerol with a molecule of ___________.

A)phosphatidylglycerol
B)phosphatidylserine
C)phosphatidylethanolamine
D)glycerol
E)a fatty acyl-CoA

Question 19

The synthesis of phosphatidylethanolamine in prokaryotes involves _________________ while in mammals _______________ occurs.

A)reaction of CDP-diacylglycerol with ethanolamine; decarboxylation of phosphatidylserine
B)decarboxylation of phosphatidylserine; reaction of CDP-ethanolamine with diacylglycerol
C)reaction of phosphoethanolamine with diacylglycerol; reaction of CDP-ethanolamine with diacylglycerol
D)decarboxylation of phosphatidylserine; reaction of CDP-diacylglycerol with ethanolamine
E)reaction of CDP-diacylglycerol with ethanolamine; reaction of phosphoethanolamine with diacylglycerol

Question 20

The synthesis of the glycosphingolipids begins with the reaction of either UDP-glucose or UDP-galactose with _____________.

A)ceramide
B)sphinganine
C)sphingosine
D)sphingomyelin
E)none of the above

Question 21

Show the reaction catalyzed by 3-hydroxy-3-methylglutrayl-CoA reductase.

Question 22

In eukaryotes, the conversion of DHAP to 1-acylglycerol-3-phosphate is a two-step process. Show the reactants and products missing in the following scheme.

Question 23

What classification is given to the following molecule?

A)a prostaglandin G derivative
B)a prostaglandin E derivative
C)a leukotriene
D)a thromboxane
E)none of the above

Question 24

The synthesis of which of the following molecules would be inhibited by aspirin?

A)prostaglandin F_{2 $\alpha$}
B)prostaglandin D₂
C)prostaglandin E₂
D)prostaglandin H₂
E)all of the above

Question 25

Show the products of the following reaction and name them: