Deck 24: Lipid Biosynthesis

Question 1

Phosphorylation of regulatory sites on acetyl-CoA carboxylase ____ the affinity for citrate and ____ the affinity for fatty acyl-CoAs requiring ____ levels of fatty acyl-CoAs for inhibition.

A) increases; decreases; low
B) decreases; increases; high
C) decreases; increases; low
D) increases; decreases; high
E) none are correct

Answer 1

C

Question 2

Acetyl-CoA carboxylase in animals is regulated by all of the following EXCEPT:

A) allosterically stimulated by citrate.
B) phosphorylation by protein kinase A.
C) allosterically inhibited by palmitoyl-CoA.
D) allosterically stimulated by ATP.
E) all are correct.

Answer 2

D

Question 3

In fatty acid synthase, the correct sequence of enzyme catalyzed reactions are:
A)β-ketoacyl-ACP synthase
B)β-ketoacyl reductase
C)β-hydroxyacyl dehydratase
D)enoyl reductase
E)acetyl transferase

A) A, B, C, D, E
B) C, B, D, E, A
C) B, A, C, D, E
D) A, C, B, E, D
E) D, E, A, B, C

Answer 3

A

Question 4

What type of linkage occurs between ACP and the intermediates in fatty acid biosynthesis?

A) an ester
B) a thioester
C) an amide
D) an ether
E) an acetal

Question 5

Which of the following statements regarding phosphorylation of acetyl-CoA carboxylase is correct?

A) phosphorylation causes activation only in the presence of palmitoyl-CoA
B) phosphorylation is a result of glucagon binding to its receptor
C) high [citrate] inhibits the phosphorylated form
D) phosphorylation causes separation of the polymeric form of the enzyme to inactive protomers
E) both b and d are true

Question 6

The main source(s) of NADPH for fatty acid biosynthesis is (are):

A) TCA cycle.
B) oxidative phosphorylation.
C) malic enzyme and the pentose phosphate pathway.
D) the conversion of OAA to malate by malate dehydrogenase.
E) glycolysis.

Question 7

E. coli does NOT have any ____ fatty acids, plants can introduce double bonds into fatty acids between Δ⁹ and the ____-end of the chain, while mammals can only introduce double bonds between Δ⁹ and the ____-end of the chain.

A) saturated; carboxyl; methyl
B) mono-unsaturated; carboxyl; methyl
C) polyunsaturated; carboxyl; methyl
D) polyunsaturated; methyl; carboxyl
E) saturated; methyl; carboxyl

Question 8

There is no transporter for acetyl-CoA to exit the mitochondria, so the carbons must be converted to ____ for transport to the cytosol.

A) acetone
B) butyrate
C) citrate
D) pyruvate
E) malonate

Question 9

The committed step in fatty acid biosynthesis, formation of malonyl-CoA, is catalyzed by:

A) fatty acid synthase.
B) pyruvate carboxylase.
C) propionate carboxylase.
D) acetyl-CoA carboxylase.
E) ATP-citrate lyase.

Question 10

All are characteristic of acetyl-CoA carboxylase EXCEPT:

A) allosteric inhibition by palmitoyl-CoA.
B) biotin carboxylase and transcarboxylase subunits.
C) biotin carboxyl carrier protein subunits.
D) citrate shifts the enzyme toward the active polymer.
E) all are correct.

Question 11

The formation of acetoacetyl-ACP is catalyzed by:

A) β-ketoacyl-ACP synthase (KSase).
B) acetyl-CoA carboxylase.
C) acetyl transacylase.
D) β-hydroxyacyl dehydratase.
E) β-ketoacyl reductase.

Question 12

The coenzyme(s) of acetyl-CoA carboxylase is/are:

A) biotin and NAD⁺.
B) TPP.
C) NADH and FAD.
D) TPP and folic acid.
E) biotin.

Question 13

Fatty acid synthase (FAS) differs from β-oxidation in all of the following ways EXCEPT:

A) occurs in cytosol.
B) uses NADPH for oxidoreductase reactions.
C) acyl carrier protein linked intermediates.
D) all of the enzymes are on one polypeptide.
E) all are true.

Question 14

In E. coli, β-hydroxydecanoyl-ACP is dehydrated by β-hydroxydecanoyl thioester dehydrase to form a double bond ____ to the thioester in the ____ configuration which is further elongated to form ____.

A) α,β; cis; palmitoyl-ACP
B) β,γ; cis; palmitoleoyl-ACP
C) β,γ; trans; palmitoleoyl-ACP
D) α,β; trans; palmitoleoyl-ACP
E) β,γ; cis; palmitoyl-ACP

Question 15

Reducing equivalents derived from glycolysis in the form of NADH can be transformed into ____ for fatty acid biosynthesis by the combined actions of ____ and ____.

A) NADPH; malate dehydrogenase; malic enzyme
B) NADPH; malate dehydrogenase; malic enzyme
C) ATP; malate dehydrogenase; malic enzyme
D) NADH; glyceraldehyde-3-phosphate dehydrogenase; malate dehydrogenase
E) NADPH; glyceraldehyde-3-phosphate dehydrogenase; malate dehydrogenase

Question 16

All of the following are characteristics of arachidonic acid EXCEPT:

A) it contains five cis-double bonds.
B) it is a precursor of leukotrienes and most prostaglandins.
C) it is an omega-6 fatty acid.
D) it can be synthesized from linoleic acid in mammals.
E) all are correct.

Question 17

Stearoyl-CoA desaturase has all of the following characteristics EXCEPT:

A) NADH and O₂ are required.
B) produces a trans double bond.
C) involves cytochrome b₅ reductase.
D) involves cytochrome b₅.
E) occurs in the endoplasmic reticulum.

Question 18

Acyl carrier protein has the same ____ group as the "business end" of ____.

A) thiamin; TPP
B) biotin; acetyl-CoA carboxylase
C) phosphoadenosine; cAMP
D) pyridoxal phosphate; vitamin B₆
E) phosphopantetheine; CoA

Question 19

The reaction catalyzed by ____ is: Citrate + ATP +CoA → acetyl-CoA + ____ + ____.

A) citrate synthase; malate; AMP + P_i
B) citrate synthase; OAA; AMP + PP_i
C) ATP-citrate lyase; OAA; AMP + PP_i
D) ATP-citrate lyase; OAA; ADP + P_i
E) citrate synthase; OAA; ADP + P_i

Question 20

Which of the following is true regarding fatty acid elongation?

A) malonyl CoA provides 2 carbons for each round of elongation
B) two reductions take place with both reactions using NADPH as the source of electrons
C) the fatty acid that is being elongated is attached to CoA
D) occurs only in cytosol
E) by not performing the second reduction reaction, an unsaturated fatty acid with a cis double bond can be formed

Question 21

The PRIMARY site, but not the only site, of cholesterol synthesis is:

A) heart.
B) intestine.
C) muscle.
D) liver.
E) adipose.

Question 22

The committed step in cholesterol biosynthesis is catalyzed by:

A) HMG-CoA synthase.
B) mevalonate kinase.
C) HMG-CoA reductase.
D) squalene monooxygenase.
E) HMG-CoA lyase.

Question 23

Regulation of fatty acid synthesis in humans is affected by all of the following EXCEPT:

A) malonyl-CoA binding to carnitine acyltransferase inhibits available substrate for β-oxidation.
B) citrate stimulates acetyl-CoA carboxylase.
C) acyl-CoAs are inhibitors of acetyl-CoA carboxylase.
D) insulin receptor binding maintains acetyl-CoA carboxylase in the inactive form.
E) glucagon promotes phosphorylation and inactivation of acetyl-CoA carboxylase.

Question 24

____ are all derived from 20-carbon fatty acids that are acylated to membrane phospholipids and released by the enzyme ____.

A) Arachidonates; triacylglycerol lipase
B) Arachidonates; phospholipase A₁
C) Eicosanoids; phospholipase A₁
D) Eicosanoids; phospholipase A₂
E) Arachidonates; phospholipase A₂

Question 25

Which of the following is correctly paired with its effect upon fatty acid synthesis?

A) palmitoyl CoA: activates
B) glucagon: activates
C) insulin: inhibits
D) citrate: activates
E) NADPH: inhibits

Question 26

The carbons of sphinganine are derived from:

A) palmitate and glycerol.
B) arachidonate and glycine.
C) fatty alcohol and dihydroxyacetone phosphate (DHAP).
D) palmitate and serine.
E) none of the above.

Question 27

All are regulatory mechanisms of HMG-CoA reductase EXCEPT:

A) low [cholesterol] increases mRNA for HMG-CoA reductase.
B) high [cholesterol] increases half-life for HMG-CoA reductase.
C) high [cholesterol] results in lower mRNA for HMG-CoA reductase.
D) phosphorylation by cAMP cascade inactivates HMG-CoA reductase.
E) phosphatases activate HMG-CoA reductase.

Question 28

An important mechanism of arachidonate release and eicosanoid synthesis involves ____ and ____.

A) insulin release; high blood sugar
B) glucagon release; low blood sugar
C) tissue injury; low blood sugar
D) inflammation; tissue injury
E) all are true

Question 29

All are true for aspirin EXCEPT:

A) it does not affect the peroxidase activity of prostaglandin endoperoxide synthase (COX).
B) it inhibits the activity of prostaglandin endoperoxide synthase (COX).
C) it stimulates ring opening in prostaglandin synthesis.
D) it acetylates the serine in the active site of the cyclooxygenase (COX).
E) it is classed as a non-steroidal anti-inflammatory drug (NSAID).

Question 30

A lipid that does NOT have a sphingosine backbone is:

A) ganglioside GM₁.
B) sphingomyelin.
C) phosphatidylinositol.
D) ceramide.
E) cerebroside.

Question 31

Which of the following statements concerning eicosanoids is correct?

A) all thromboxanes contain a 1,3-dioxane ring
B) all prostaglandins contain a cyclic ether
C) all leukotrienes contain three conjugated double bonds
D) leukotirenes are derived from prostaglandin H₂ while thromboxanes are derived from arachidonic acid
E) none of the above

Question 32

Platelet-activating factor displays dramatic ability to ____ blood vessels and thus ____ blood pressure, and to aggregate platelets.

A) dilate; reduce
B) dilate; reduce
C) constrict; increase
D) constrict; increase
E) constrict; increase

Question 33

Insulin promotes the ____ of acetyl-CoA carboxylase and ____ of triacylglycerol lipase by ____ the phosphodiesterases that converts cAMP to AMP.

A) activation; inactivation; stimulating
B) inactivation; activation; stimulating
C) inactivation; activation; inhibiting
D) activation; inactivation; inhibiting
E) none are true

Question 34

Both glycerol and dihydroxyacetone phosphate can serve as precursors for phosphatidic acid. Which enzyme is NOT USED to catalyze reactions in the synthesis of phosphatidic acid from these two precursors?

A) glycerol kinase
B) triose phosphate isomerase
C) acyldihydroxyacetone-P reductase
D) glycerol-3-phosphate acyltransferase
E) 1-acylglycerol-3-phosphate acyltransferase

Question 35

CDP-diacylglycerols are precursors for the synthesis of all EXCEPT:

A) phosphatidylethanolamine.
B) phosphatidyl glycerol.
C) cardiolipins.
D) phosphatidylinositol.
E) all are true.

Question 36

All are characteristics of COX-2 inhibitors EXCEPT:

A) selectively block inflammation mediated by COX-2.
B) are NSAIDs.
C) less potential for stomach lesions than aspirin.
D) less renal toxicity than COX-1 inhibitors.
E) all are correct.

Question 37

Components for plasmalogen biosynthesis include all EXCEPT:

A) CDP-ethanolamine.
B) fatty acyl-CoA.
C) NADPH, NADH and O₂.
D) long-chain alcohol.
E) glycerol.

Question 38

The correct sequence for synthesis of mevalonate from acetyl-CoA is:
A)HMG-CoA synthase
B)formation of 3-hydroxy-3-methylglutaryl-CoA
C)β-ketothiolase catalyzed condensation
D)HMG-CoA reductase activity
E)Formation of acetoacetyl-CoA

A) E, C, D, A, B
B) C, D, A, B, E
C) E, B, A, C, D
D) E, A, B, D, C
E) C, E, A, B, D

Question 39

Sphinganine is acylated in the ____-position.

A) 3-OH
B) 2-NH₂
C) 1-OH
D) 3-NH₂
E) all are true

Question 40

In eukaryotes, phosphatidic acid is converted directly either to ____ or to ____ from which all other ____ are derived.

A) triacylglycerols; monoacylglycerols; acylglycerols
B) acylglycerols; phospholipids; glycerophospholipids
C) monoacylglycerols; phospholipids; glycerophospholipids
D) diacylglycerols; CDP-diacylglycerols; glycerophospholipids
E) diacylglycerols; CDP-diacylglycerols; acylglycerols

Question 41

Which of the following lipoproteins is INCORRECTLY defined?

A) chylomicron: transport of dietary lipids to the liver
B) HDL: scavenger of extra-hepatic cholesterol
C) LDL: transport of cholesterol to extra-hepatic tissue
D) VLDL: transport of triacylglycerols from the liver
E) all of the above are correct

Question 42

Which of the following molecules would have an inhibitory effect upon the overall process of fatty acid synthesis?

A) citrate
B) insulin
C) palmitoyl CoA
D) NADPH
E) none of the above

Question 43

The "statins" are a series of drugs used to:

A) inhibit fatty acid synthesis in diet drugs.
B) widely prescribed drugs used to inhibit squalene monooxygenase.
C) derivatives or mimics of mevinolin used to inhibit HMG-CoA reductase.
D) derivatives of cholesterol used to lower cholesterol levels.
E) none are true.

Question 44

Lipoprotein lipase hydrolyzes ____ from VLDL particles to convert the VLDL into ____.

A) cholesterol esters; HDL particles
B) cholesterol esters; LDL particles
C) triacylglycerols; LDL particles
D) triacylglycerols; chylomicrons
E) triacylglycerols; HDL particles

Question 45

____ is an intermediate on the biosynthetic pathway from cholesterol to both male and female hormones.

A) Aldosterone
B) Progesterone
C) Cortisol
D) Estradiol
E) Testosterone

Question 46

All are correct for bile salts EXCEPT:

A) made by the liver and utilized in the intestine.
B) derived from cholesterol.
C) conjugates of bile acids with glycine and taurine.
D) highly effective as detergents.
E) insert well into membranes because they are strictly nonpolar.

Question 47

Which of the following is FALSE regarding HDL pariticales?

A) high HDL levels correlates with high risk of cardiovascular disease.
B) an HDL life span is typically 5 to 6 days.
C) they are initially formed as HDL precursors that contains no cholesterol or cholesterol esters.
D) scavenges excess cholesterol from extrahepatic tissue and returns cholesterol and cholesterol esters to liver.
E) accumulates cholesterol esters via LCAT action.

Question 48

Which of the following catalyzes the conversion of cholesterol to pregnenolone, the first step in the conversion of cholesterol to steroid based hormones?

A) 7-α-hydroxylase
B) desmolase
C) steroid 5-α-reductase
D) aromatase
E) 17-ketoreductase

Question 49

Dietary lipids are "packaged" in the intestine into ____ for transport via the lymphatic system.

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

Question 50

All are true for the action of cortisol EXCEPT:

A) stimulates gluconeogenesis and glycogen synthesis in liver.
B) inhibits protein synthesis and stimulates protein degradation in muscle.
C) inhibits allergic and inflammatory responses.
D) exerts an immunosuppressive effect and an inhibition of wound healing.
E) all are true.

Question 51

Order the lipoproteins from lowest density to highest density.
A)chylomicrons
B)HDL
C)IDL
D)VLDL
E)LDL

A) D, A, E, B, C
B) D, E, C, B, A
C) A, E, B, D, C
D) D, C, A, E, B
E) A, D, C, E, B

Question 52

The major circulatory complex for cholesterol and cholesterol esters that is often referred to a "bad cholesterol" is the:

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

Question 53

Characteristics of squalene monooxygenase include all EXCEPT:

A) requires a soluble protein activator.
B) bound to the endoplasmic reticulum (ER).
C) uses FAD and NADPH.
D) requires O₂.
E) all are true.

Question 54

Characteristics of mixed-function oxidases include all EXCEPT:

A) usually involve cytochrome P-450.
B) often catalyze hydroxylation reactions on ring-systems such as sterols.
C) use both NADPH and O₂.
D) one product is CO₂.
E) all are correct.

Question 55

Which of the following is correctly paired with its precursor?

A) cholesterol → palmitic acid
B) arachidonic acid → prostaglandins
C) testosterone → progesterone
D) aldosterone → cholic acid
E) none of the above

Question 56

The appropriate sequence of intermediates between mevalonate and squalene are:
A)geranyl pyrophosphate
B)isopentenyl pyrophosphate
C)5-phosphomevalonate
D)farnesyl pyrophosphate
E)dimethylallyl pyrophosphate

A) A, C, D, B, E
B) C, B, E, A, D
C) C, E, A, D, B
D) E, C, B, D, A
E) B, C, D, A, E

Question 57

The general genetic defect responsible for ____ is the absence or dysfunction of ____ in the body such that blood cholesterol levels are typically 300 to over 800 mg/dL.

A) hypocholesterolemia; triacylglycerol lipase
B) hypercholesterolemia; lipoprotein lipase
C) LCAT; LDL receptors
D) familial hypercholesterolemia; LDL receptors
E) familial hypocholesterolemia; HDL receptors

Question 58

Lipoproteins consist of a core of ____ and ____ surrounded by a single layer of ____, into which is inserted ____ and ____.

A) proteins; triacylglycerols; cholesterol esters; phospholipids; cholesterol
B) triacylglycerols; cholesterol esters; phospholipids; proteins; cholesterol
C) phospholipids; cholesterol esters; triacylglycerols; proteins; cholesterol
D) cholesterol esters; proteins; cholesterol; phospholipids; triacylglycerols
E) triacylglycerols; cholesterol; proteins; cholesterol esters; phospholipids

Question 59

Male baldness, prostate hyperplasia and prostate cancer have been implicated in elevated levels of ____ and treatment involves inhibition of ____.

A) glucocorticoids; gluconeogenesis
B) stanozolol; lactate dehydrogenase
C) dihydrotestosterone; steroid 5α-reductase
D) cholesterol; mevinolin
E) none of the above

Question 60

Properties of progesterone include all EXCEPT:

A) produced from pregnenolone in ER.
B) synthesis in the adrenal cortex activated by ACTH.
C) prepares the uterus for attachment of a fertilized ovum.
D) secreted from corpus luteum in late menstrual cycle.
E) all are true.

Question 61

The role of citrate in fatty acid synthesis makes it an important regulator of the process. Which of the following enzymes would be allosterically activated by citrate?

A) Citrate lyase
B) Malic enzyme
C) Acetyl-CoA carboxylase
D) β-ketoacyl-ACP synthase
E) None of the above

Question 62

Discuss the condensation of two farnesyl pyrophospahates to produce squalene.​

Question 63

How many NADPH are required to make one molecule of palmitic acid from acetyl CoA?

A) 7
B) 8
C) 14
D) 16
E) 21

Question 64

How does phosphorylation affect the activity of acetyl-CoA carboxylase?​

Question 65

Which of the following CANNOT be made from acetyl CoA?

A) cholesterol
B) pyruvate
C) acetoacetate
D) squalene
E) palmitate

Question 66

Discuss sphingolipids and their synthesis.​

Question 67

Which of the following statements is true regarding lipid metabolism?

A) The synthesis of one molecule of cholesterol requires 5 molecules of mevalonate
B) The synthesis of fatty acids from acetyl CoA involves reduction by NADPH and FADH₂
C) Synthesis of fatty acids involves a coordinated effort of fatty acid synthase complex and the acyl carrier protein
D) The conversion of lanosterol to cholesterol requires only 4 steps, two that remove methyl groups, an isomerization, and a reduction
E) The synthesis of fatty acids involves a series of reactions catalyzed by several separate enzymes, thus requiring the substrates to diffuse from one enzyme to the next

Question 68

Discuss the functions of glucocorticoids.​

Question 69

What are low-density lipoproteins (LDLs)? How are they degraded in cells?​

Question 70

HMG-CoA reductase, the regulatory enzyme for the synthesis of cholesterol, is inhibited by simvastatin. Based upon the structure of the product, mevalonate, and the structure of simvastatin, what sort of enzyme inhibition would be produced by simvastatin?

A) competitive
B) non-competitive
C) uncompetitive
D) mechanism-based inactivator
E) none of the above