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93 Cards in this Set

  • Front
  • Back
All of the following statements about acetyl-CoA carboxylase are correct except:
a. It catalyzes the rate-limiting step of fatty acid synthesis.
b. It requires biotin.
c. It is inhibited by cAMP-mediated phosphorylation.
d. It is activated by palmitoyl CoA.
e. Its content in a cell responds to changes in fat content in the diet.
d. It is activated by palmitoyl CoA.
It is activated by citrate and inhibited by long chain fatty acyl CoAs.
During the synthesis of palmitate in liver cells:
a. The addition of malonyl CoA to fatty acid synthase elongates the growing chain by three carbon atoms.
b. A β-keto acyl residue on the 4’-phosphopantetheine moiety is ultimately reduced to a saturated residue by NADPH.
c. Palmitoyl CoA is released from the synthase.
d. Transfer of the growing chain from ACP to another –SH occurs after addition of the next malonyl CoA.
e. The first compound to add to fatty acid synthase is malonyl CoA.
b. A β-keto acyl residue on the 4’-phosphopantetheine moiety is ultimately reduced to a saturated residue by NADPH.
In humans, desaturation of fatty acids:
a. Occurs primarily in mitochondria.
b. Is catalyzed by an enzyme system that uses NADPH and a cytochrome.
c. Introduces double bonds primarily of trans configuration.
d. Can occur only after palmitate has been elongated to stearic acid.
e. Introduces the first double bond at the methyl end of the molecule.
b. Is catalyzed by an enzyme system that uses NADPH and a cytochrome.
All of the following events are usually involved in the synthesis of triacylglycerols in adipose tissue except:
a. Addition of a fatty acyl CoA to a diacylglycerol.
b. Addition of a fatty acyl CoA to a lysophosphatide.
c. A reaction catalyzed by glycerol kinase.
d. Hydrolysis of phosphatidic acid by a phosphatase.
e. Reduction of dihydroxyacetone phosphate.
c. A reaction catalyzed by glycerol kinase.
This does not occur to any significant adipose tissue.
Lipoprotein lipase:
a. Is an intracellular enzyme.
b. Is stimulated by cAMP-mediated phosphorylation.
c. Functions to mobilize stored triacylglycerols from adipose tissue.
d. Is stimulated by one of the apoproteins present in VLDL.
e. Produces free fatty acids and a monoacylglycerol.
d. Is stimulated by one of the apoproteins present in VLDL.
ApoC-II binds to the lipoprotein to the enzyme.
The high glucagon/insulin ratio seen in starvation:
a. Promotes mobilization of fatty acids from adipose stores.
b. Stimulates β-oxidation by inhibiting the production of malonyl CoA.
c. Leads to increased concentrations of ketone bodies in the blood.
d. All of the above.
e. None of the above.
d. All of the above.
A high glucagon/insulin ratio results in cAMP-mediated phosphorylations that activate hormone-sensitive lipase in adipose tissue and inhibit acetyl CoA carboxylase in liver, leading to mobilization of fatty acids from adipose tissue and decreased malonyl CoA in liver. The fall in malonyl CoA causes derepression of CPT I activity, allowing accelerated production of acetyl CoA in the mitochondria, and ultimately ketone bodies, from the mobilized fatty acids.
A deficiency of carnitine might be expected to interfere with:
a. β-oxidation.
b. Ketone body formation from acetyl CoA.
c. Palmitate synthesis.
d. Mobilization of stored triacylglycerols from adipose tissue.
e. Uptake of fatty acids into cells from the blood.
a. β-oxidation.
Carnitine functions in transport of fatty acyl CoA esters formed in cytosol into the mitochondria.
The child was diagnosed with carnitine-acylcarnitine translocase deficiency. The dietary treatment was beneficial because:
a. The child could get all required energy from carbohydrate.
b. The deficiency was in the peroxisomal system so carnitine would not be helpful.
c. Medium-chain fatty acids (8-10 carbons) enter the mitochondria before being converted to their CoA derivatives.
d. Medium-chain triacylglycerols contain mostly hydroxylated fatty acids.
e. Medium-chain fatty acids such as C8 and C10 are readily converted into glucose by the liver.
c. Medium-chain fatty acids (8-10 carbons) enter the mitochondria before being converted to their CoA derivatives.
Because medium-chain fatty acids cross the mitochondrial membrane directly, they do not require the carnitine system.
β-oxidation of fatty acids:
a. Generates ATP only if acetyl CoA is subsequently oxidized.
b. Is usually suppressed during starvation.
c. Uses only even-chain, saturated fatty acids as substrates.
d. Uses NADP+.
e. Occurs by a repeated sequence of four reactions.
e. Occurs by a repeated sequence of four reactions.
The lack of ketone in the presence of low blood glucose in this case is unusual since ketone body concentrations usually increase with fasting-induced hypoglycemia. Ketone bodies:
a. Are formed by removal of CoA from the corresponding intermediate of β-oxidation.
b. Are synthesized from cytoplasmic β-hydroxy-β-methyl glutaryl coenzyme A (HMG-CoA).
c. Are synthesized primarily in muscle tissue.
d. Include both β-hydroxybutyrate and acetoacetate, the ratio reflecting the intramitochondrial [NADH]/ [NAD+] ratio in the liver.
e. Form when β-oxidation is interrupted.
d. Include both β-hydroxybutyrate and acetoacetate, the ratio reflecting the intramitochondrial [NADH]/ [NAD+] ratio in the liver.
α-Oxidation:
a. Is important in the metabolism of branched-chain fatty acids.
b. Metabolizes a fatty acid completely to acetyl CoA.
c. Produces hydrogen peroxide.
d. Prevents the fatty acid from producing energy.
e. Requires NADPH.
a. Is important in the metabolism of branched-chain fatty acids.
The presence of a methyl group precludes the beta-oxidation process at that point.
Another minor pathway of fatty acid oxidation, ω-oxidation, also results in a hydroxylation. ω-Oxidation:
a. Occurs in mitochondria.
b. Introduces the –OH on the carbon adjacent to the carboxyl group.
c. Oxidizes primarily very-long-chain fatty acids.
d. Oxidizes the terminal methyl group.
e. Produces dicarboxylic acids in the initial oxidation.
d. Oxidizes the terminal methyl group.
This is why it is called ω-oxidation
Roles of various phospholipids include all of the following except:
a. Cell-cell recognition.
b. A surfactant function in lung.
c. Activation of certain membrane enzymes.
d. Signal transduction.
e. Mediator of hypersensitivity and acute inflammatory reactions.
a. Cell-cell recognition.
This function appears to be associated with complex glycosphingolipids.
CDP-X (where X is the appropriate alcohol) reacts with 1,2-diacylglycerol in the primary synthetic pathway for:
a. Phosphatidylcholine.
b. Phosphatidylinositol.
c. Phosphatidylserine.
d. All of the above.
e. None of the above.
a. Phosphatidylcholine.
This is the main pathway for choline.
Phospholipases A1 and A2:
a. Have no role in phospholipid synthesis.
b. Are responsible for initial insertion of fatty acids in sn-1 and sn-2 positions during synthesis.
c. Are responsible for base exchange in the interconversion of phosphatidylethanolamine and phosphatidylserine.
d. Hydrolyze phosphatidic acid to a acylglycerol.
e. Remove a fatty acid in an sn-1 or sn-2 position so it can be replaced by another in phospholipid synthesis.
e. Remove a fatty acid in an sn-1 or sn-2 position so it can be replaced by another in phospholipid synthesis.
Phospholipase A1 and A2, as their names imply, hydrolyze a fatty acid from a phospholipid and so are part of phospholipid degradation. They are also important in synthesis, however, in ensuring the asymmetric distribution of fatty acids that occurs in phospholipids.
Bile acids differ from their precursor cholesterol in that they:
a. Are not amphipathic.
b. Contain an ionizable carboxyl group.
c. Contain less oxygen.
d. Are synthesized primarily in the intestine.
e. Contain more double bonds.
b. Contain an ionizable carboxyl group.
This carboxyl group is often conjugated to glycine or taurine.
A ganglioside may contain all of the following except:
a. A ceramide structure.
b. Glucose or galactose.
c. Phosphate.
d. One or more sialic acids.
e. Sphingosine.
c. Phosphate.
Glycosphingolipids do not contain phosphate.
Phosphatidlyinositols:
a. Are neutral phospholipids.
b. Are found primarily in mitochondrial membrane.
c. Release Ca2+ from the endoplasmic reticulum.
d. Can serve to anchor glycoproteins to cell surfaces.
e. Are the major surfactants maintaining normal lung function.
d. Can serve to anchor glycoproteins to cell surfaces.
Glycerol-phosphatidylinositol anchors have specific structural features.
Prostaglandin synthase, a bifunctional enzyme:
a. Catalyzes rate-limiting step of prostaglandin synthesis.
b. Is inhibited by anti-inflammatory steroids.
c. Contains both a cyclooxygenase and a peroxidase component.
d. Produces PGG2 as the end product.
e. Uses as substrate the pool of free arachidonic acid in the cell.
c. Contains both a cyclooxygenase and a peroxidase component.
Cyclooxygenase oxidizes arachidonic acid and peroxidase converts PGG2 to PGH2.
Hydroperoxyeicosatetraenoic acids (HPETEs):
a. Are derived from arachidonic acid by peroxidase reaction.
b. Are mediators of hypersensitivity reactions.
c. Are intermediates in formation of leukotrienes.
d. Are relatively stable compounds (persist for as long as 4 hours).
e. Are inactivated forms of leukotrienes.
c. Are intermediates in formation of leukotrienes.
These are formed by addition of oxygen to arachidonic acid.
In biosynthesis of cholesterol:
a. 3-hydroxy-3-methyl glutaryl CoA (HMG CoA) is synthesized by mitochondrial HMG CoA synthase.
b. HMG-CoA reductase catalyzes the rate-limiting step.
c. The conversion of mevalonic acid to farnesyl pyrophosphate proceeds via condensation of 3 molecules of mevalonic acid.
d. Condensation of 2 farnesyl pyrophosphates to form squalene is freely reversible.
e. Conversion of squalene to lanosterol is initiated by formation of the fused ring system, followed by addition of oxygen.
b. HMG-CoA reductase catalyzes the rate-limiting step.
This enzyme is inhibited by cholesterol.
Cholesterol present in LDL (low-density lipoproteins):
a. Binds to a cell receptor and diffuses across the cell membrane.
b. When it enters a cell, suppresses activity of ACAT (acyl-CoA-cholesterol acyl transferase).
c. Once in the cell is converted to cholesteryl esters by LCAT (lecithin-cholesterol acyl transferase).
d. Once it has accumulated in the cell, inhibits replenishment of LDL receptors.
e. Represents primarily cholesterol that is being removed from peripheral cells.
d. Once it has accumulated in the cell, inhibits replenishment of LDL receptors.
This is one of the ways to prevent overload in the cell.
All of the following are true about degradation of sphingolipids except it:
a. Occurs by hydrolytic enzymes contained in lysosomes.
b. Terminates at level of ceramides.
c. Is a sequential, stepwise removal of constituents.
d. May involve a sulfatase or a neuraminidase.
e. Is catalyzed by enzymes specific for a type of linkage rather than specific compound.
b. Terminates at level of ceramides.
Ceremides are hydrolyzed to sphingosine and fatty acid.
In Niemann-Pick disease, the deficient enzyme is sphingomyelinase. Sphingomyelins differ from other sphingolipids in that they are:
a. Not based on a ceramide core.
b. Acidic rather than neutral at physiological pH.
c. Only types containing N-acetylneuraminic acid.
d. Only types that are phospholipids.
e. Not amphipathic.
d. Only types that are phospholipids.
Sphingomyelins are not glycosphingolipids but phosphosphingolipids.
Aminotransferases:
a. Usually require α-ketoglutarate or glutamine as one of the reacting pair.
b. Catalyze reactions that result in a net use or production of amino acids.
c. Catalyze irreversible reactions.
d. Require pyridoxal phosphate as an essential cofactor for the reaction.
e. Are not able to catalyze transamination reactions with essential amino acids.
d. Require pyridoxal phosphate as an essential cofactor for the reaction.
The mechanism of action begins with the formation of a Schiff base with pyridoxal phosphate.
The production of ammonia in the reaction catalyzed by glutamate dehydrogenase:
a. Requires the participation of NADH or NADPH.
b. Proceeds though a Schiff base intermediate.
c. May be reversed to consume ammonia if it is present in excess.
d. Is favored by high levels of ATP or GTP.
e. Would be inhibited when gluconeogenesis is active.
c. May be reversed to consume ammonia if it is present in excess.
This is an important mechanism for reducing toxic ammonia concentrations.
All of the following are correct about ornithine except it:
a. May be formed from or converted to glutamic semialdehyde.
b. Can be converted to proline.
c. Plays a major role in the urea cycle.
d. Is a precursor of putrescine, a polyamine.
e. Is in equilibrium with spermidine.
e. Is in equilibrium with spermidine.
Spermidine is formed by adding propylamine to putrescine.
S-Adenosylmethionine:
a. Contains a sulfonium ion that carries the methyl group to be transferred.
b. Yields α-ketobutyrate in the reaction in which the methyl is transferred.
c. Donates a methyl group in a freely reversible reaction.
d. Generates H2S by transsulfuration.
e. Provides the carbons for the formation of cysteine.
a. Contains a sulfonium ion that carries the methyl group to be transferred.
The reactive, positively charged sulfur reverts to a neutral thioether when the methyl group is transferred to an acceptor.
Lysine:
a. May be replaced by its α-keto acid analogue in the diet.
b. Produces pyruvate and acetoacetyl CoA in its catabolic pathway.
c. Is methylated by S-adenosylmethionine.
d. Is the only one of the common amino acids that is a precursor of carnitine.
e. All of the above are correct.
d. Is the only one of the common amino acids that is a precursor of carnitine.
Free lysine is not methylated, but lysyl residues in a protein are methylated in a posttranslational modification. Intermediates of carnitine synthesis are derived from trimethyllysine liberated by proteolysis.
Glutathione does all of the following except:
a. Participate in the transport of amino acids across some cell membranes.
b. Scavenge peroxides.
c. Form conjugates with some drugs to increase water solubility.
d. Decreases the stability of erythrocyte membranes.
e. Acts as cofactor for some enzymes.
d. Decreases the stability of erythrocyte membranes.
Most of the functions of glutathione listed are dependent upon the sulfhydryl group (-SH). It increases the membrane stability. Glutathione reductase helps to maintain the ratio of GSH:GSSG at about 100:1.
All of the following are true about the branched-chain amino acids except they:
a. Are essential in the diet.
b. Differ in that one is glucogenic, one is ketogenic, and one is classified as both.
c. Are catabolized in a manner that bears a resemblance to β-oxidation of fatty acids.
d. Are oxidized by a dehydrogenase complex to branched-chain acyl CoAs one carbon shorter than the parent compound.
e. Are metabolized initially in the liver.
e. Are metabolized initially in the liver.
Valine and isoleucine give rise to propionyl CoA, a precursor of Succinyl CoA. A disease related to a defect in this conversion is methylmalonic aciduria. Some patients respond to megadoses of vitamin B12. Which of the following statements about the conversion of propionyl CoA to Succinyl CoA is/are correct?
a. The first step in the conversion is a biotin-dependent carboxylation.
b. Some methylmalonic aciduria patients respond to B12 because the defect in the mutase converting malonyl CoA to succinyl CoA is poor binding of the cofactor.
c. The same pathway of propionyl CoA to succinyl CoA is part of the metabolism of odd-chain fatty acids.
d. All of the above are correct.
e. None of the above are correct.
d. All of the above are correct.
In the formation of urea from ammonia, all of the following are correct except:
a. Aspartate supplies one of the nitrogens found in urea.
b. This is an energy-expensive process, utilizing several ATP’s.
c. The rate of the cycle fluctuates with the diet.
d. Fumarate is produced.
e. Ornithine transcarbamoylase catalyzes the rate-limiting step.
e. Ornithine transcarbamoylase catalyzes the rate-limiting step.
Carbamoyl phosphate synthetase I catalyzes the rate-limiting step.
Carbamoyl phosphate synthetase I:
a. Is a flavoprotein.
b. Is controlled primarily by feedback inhibition.
c. Is unresponsive to changes in arginine.
d. Requires N-acetyl glutamate as an allosteric effector.
e. Requires ATP as an allosteric effector.
d. Requires N-acetyl glutamate as an allosteric effector.
The primary control is by the allosteric effector, N-acetylglutamate.
When there is a deficiency of phenylalanine hydroxylase:
a. Tyrosine hydroxylase substitutes for it so phenylalanine levels remain constant.
b. Tyrosine is synthesized by an alternate pathway instead of from phenylalanine.
c. Light skin and hair result because the enzyme catalyzes the first step to melanins.
d. Products derived from phenylalanine transamination are excreted.
e. Phenylalanine is catabolized by monoamine oxidase.
d. Products derived from phenylalanine transamination are excreted.
This is normally not significant.
Catecholamines:
a. Production terminates with dopamine in the brain but epinephrine in the adrenal gland.
b. Production begins with the action of tyrosinase on tyrosine.
c. Are metabolized to both glucogenic and ketogenic fragments.
d. Are highly colored compounds.
e. All contain methyl groups donated by S-adenosylmethionine.
a. Production terminates with dopamine in the brain but epinephrine in the adrenal gland.
This reflects tissue specificity.
The two purine nucleotides found in RNA:
a. Are formed in a branched pathway from a common intermediate.
b. Are formed in a sequential pathway.
c. Must come from exogenous sources.
d. Are formed by oxidation of the deoxy forms.
e. Are synthesized from non-purine precursors by totally separate pathways.
a. Are formed in a branched pathway from a common intermediate.
GMP and AMP are both formed from the first purine nucleotide, IMP, in a branched pathway.
The type of enzyme known as phosphoribosyltransferase in involved in all of the following except:
a. Salvage of pyrimidine bases.
b. The de novo synthesis of pyrimidine nucleotides.
c. The de novo synthesis of purine nucleotides.
d. Salvage of purine bases.
c. The de novo synthesis of purine nucleotides.
In purine nucleotide synthesis, the purine ring is built up stepwise on ribose 5-phosphate and not transferred to it.
Uric acid is:
a. Formed from xanthine in the presence of O2.
b. A degradation product of cytidine.
c. Deficient in the condition known as gout.
d. A competitive inhibitor of xanthine oxidoreductase.
e. Oxidized, in humans, before it is excreted in urine.
a. Formed from xanthine in the presence of O2.
The xanthine oxidoreductase reaction produces uric acid.
In nucleic acid degradation, all of the following are correct except:
a. There are nucleases that are specific for either DNA or RNA.
b. Nucleotidases convert nucleotides to nucleosides.
c. The conversion of nucleoside to a free base is an example of a hydrolysis.
d. Because of the presence of deaminases, hypoxanthine rather than adenine is formed.
e. A deficiency of adenosine deaminase leads to an immunodeficiency.
c. The conversion of nucleoside to a free base is an example of a hydrolysis.
The product is ribose-1-phosphate rather than the free sugar, a phosphorylysis.
The conversion of nucleoside 5’-monophosphates to nucleoside 5’-triphosphates:
a. Is catalyzed by nucleoside kinases.
b. Is a direct equilibrium reaction.
c. Utilizes a relatively specific nucleotide kinase and a relatively nonspecific nucleoside diphosphate kinase.
d. Generally uses GTP as a phosphate donor.
e. Occurs only during the S phase of the cell cycle.
c. Utilizes a relatively specific nucleotide kinase and a relatively nonspecific nucleoside diphosphate kinase.
These two enzymes are important in interconverting the nucleotide forms.
Which of the following chemotherapeutic agents works by impairing de novo purine synthesis?
a. Acyclovir (acycloguanosine).
b. 5-fluorouracil (antimetabolite).
c. Methotrexate (antifolate).
d. Hydroxyurea.
e. AZT (3’azido-3’-deoxythymidine).
c. Methotrexate (antifolate).
Antifolates reduce the concentration of THF compounds that are necessary for two steps of purine synthesis.
Elements involved in the effectiveness of the dietary treatment uridine include:
a. Conversion of exogenous uridine to UMP by uridine phosphotransferase.
b. UTP from exogenous uridine providing substrate for synthesis of CTP.
c. Inhibition of carbamoyl phosphate synthetase II by UTP.
d. All of the above.
e. None of the above.
d. All of the above.
It is common for an exogenous agent to require conversion to an active form. In thise case the uridine is "salvaged" to the monophosphate and ultimately to the triphosphate. The cell is deficient in UTP and CTP because the conversion of orotic acid is blocked so the exogenous uridine provides a bypass around the block. Orotic acid formation is decreased since UTP inhibits carbamoyl phosphate synthetase II, the control enzyme.
In the de novo synthesis of pyrimidine nucleotides:
a. Reactions take place exclusively in the cytosol.
b. A free base is formed as an intermediate.
c. PRPP is required in the rate-limiting step.
d. UMP and CMP are formed from a common intermediate.
e. UMP inhibition of OMP-decarboxylase is the major control of the process.
b. A free base is formed as an intermediate.
This is in contrast to purine de novo synthesis.
The explanation for this difference in the two forms of gout is:
a. It is an experimental artifact and the decrease in uric acid and increase in xanthine plus hypoxanthine in non-Lesch-Nyhan gout is the same.
b. Allopurinol is less effective in non-Lesch-Nyhan gout.
c. There is an increased excretion of xanthine and hypoxanthine in non-Lesch-Nyhan gout.
d. PRPP levels are reduced in Lesch-Nyhan.
e. In non-Lesch-Nyhan gout hypoxanthine and xanthine are salvaged to IMP and XMP and inhibit PRPP amidotransferase.
e. In non-Lesch-Nyhan gout hypoxanthine and xanthine are salvaged to IMP and XMP and inhibit PRPP amidotransferase.
Not only is uric acid production directly inhibited, de novo synthesis is as well, thus reducing production of xanthine and hypoxanthine. In Lesch-Nyhan, the only effect is the direct inhibition of xanthine oxidase.
Which of the following is/are aspects of the overall regulation of de novo purine nucleotide synthesis?
a. AMP, GMP, and IMP shift PRPP amido transferase from a small form to a large form.
b. PRPP amidotransferase shows hyperbolic kinetics with PRPP.
c. AMP inhibits the conversion of IMP to GMP.
d. Change in glutamine concentration is a major regulator.
e. Direct interconversion of AMP to GMP maintains balance of the two.
a. AMP, GMP, and IMP shift PRPP amido transferase from a small form to a large form.
This is a mechanism of inhibition since the large form of the enzyme is inactive.
Which of the following statements is/are correct? Arava is an immunosuppressant and inhibitor of dihydrooroate dehydrogenase, and has the same effect as methotrexate but fewer side effects.
a. Methotrexate inhibits the de novo synthesis of UMP.
b. Arava inhibits the de novo synthesis of pyrimidine nucleotides.
c. Arava inhibits the conversion of dUMP to dTMP.
d. Methotrexate inhibits the production of tetrahydrobiopterin.
e. Both drugs greatly increase production of β-amino acids.
b. Arava inhibits the de novo synthesis of pyrimidine nucleotides.
The conversion of dihydroorotate to orotic acid is a key step in de novo synthesis of the pyrimidine nucleotides.
Deoxyribonucleotides:
a. Cannot by synthesized so they must be supplied preformed in the diet.
b. Are synthesized de novo using dPRPP.
c. Are synthesized from ribonucleotides by an enzyme system involving thioredoxin.
d. Are synthesized from ribonucleotides by nucleotide kinases.
e. Can be formed only by salvaging free bases.
c. Are synthesized from ribonucleotides by an enzyme system involving thioredoxin.
Deoxyribonucleotides are synthesized from the ribonucleoside diphosphates by nucleoside reductase that uses thioredoxin as the direct hydrogen-electron donor.
HMG-CoA
a. From the cytosol is converted to ketone bodies
b. From the mitochondria is used for cholesterol biosynthesis
c. Lyase cleaves HMG-CoA for cholesterol biosynthesis
d. Lyase cleaves HMG-CoA for ketone body synthesis
e. Combines with malonyl CoA for fatty acid biosynthesis
d. Lyase cleaves HMG-CoA for ketone body synthesis
The main function carried out by bile salts in adults is:
a. to promote lipid digestion by stimulating pancreatic lipase.
b. as emulsifiers of dietary lipids
c. to bind and transport dietary lipids into intestinal mucosal cells.
d. as precursors for cholesterol synthesis
e. to promote lipid digestion by stimulating gastric lipase.
b. as emulsifiers of dietary lipids
Fatty acids occurring in humans most commonly:
a. are limited to 16 or fewer carbon atoms.
b. are highly branched structures
c. contain an even number of carbon atoms
d. must be supplied entirely by the diet.
e. must be supplied by the diet if they contain any double bonds.
c. contain an even number of carbon atoms
Acetyl-CoA carboxylase
a. Synthesis is stimulated by a low calorie diet.
b. Requires THF as a coenzyme
c. Becomes an inactive dimer in the presence of citrate
d. is actived by dephosphoylation
e. Is the rate-limiting step in fatty acid degradation
d. is actived by dephosphoylation
________________ are the only carriers of dietary lipids in the blood.
a. LDLs
b. HDLs
c. VLDLs
d. Chylomicrons
e. Apolipoproteins
d. Chylomicrons
Which of the following is NOT true about lipid transport in the fasted state?
a. Hormone-sensitive lipase is activated by phosphorylation by cAMP dependent protein kinase A.
b. Perilipin is phophoylated by protein kinase A, and allows access of hormone sensitive lipase to triacylglycerols.
c. During prolonged fasting the liver makes ketone bodies.
d. Once hydrolyzed from TAGs fatty acids are released into the blood and transported by serum albumin.
e. Hormone-sensitive lipase is activated by insulin.
e. Hormone-sensitive lipase is activated by insulin.
How do fatty acid beta-oxidation and fatty acid biosynthesis differ in terms of cellular location?
a. both take place in the mitochondria
b. both take place in the cytosol
c. Fatty acid beta-oxidation occurs in the mitochondria, and fatty acid biosynthesis occurs in the cytoplasm
d. Fatty acid beta-oxidation occurs in the cytosol and fatty acid biosynthesis occurs in the mitochondria.
e. Fatty acid beta-oxidation occurs in lysosomes, and fatty acid biosynthesis occurs in chylomicrons.
c. Fatty acid beta-oxidation occurs in the mitochondria, and fatty acid biosynthesis occurs in the cytoplasm
Triacylglycerol synthesis occurs primarily in all but which of the following?
a. liver
b. adipose tissue
c. mature erythrocytes
d. lactating mammary glands
e. intestinal mucosal cells
c. mature erythrocytes
Where do the carbon and two nitrogens of urea originate from?
a. Carbamoyl phosphate, aspartate, arginine
b. carbamoyl phosphate, free ammonia, arginine
c. bicarbonate, free ammonia, glutamate
d. bicarbonate, free ammonia, aspartate
e. THF, free ammonia, glutamate
d. bicarbonate, free ammonia, aspartate
Which of the following is NOT true about the transport of ammonia?
a. Fifty percent of circulating amino acid molecules are glutamine.
b. The enzyme glutaminase occurs in the liver and kidneys.
c. Glutamine sythetase is responsible for the synthesis of glutamine from glutamate and ammonia.
d. Pyruvate is transaminated to form alanine.
e. Because ammonia is constantly produced in tissues it is present very high levels in the blood.
e. Because ammonia is constantly produced in tissues it is present very high levels in the blood.
In the urea cycle
a. enzymes are inhibited (10-20 fold) when delivery of ammonia or amino acids to the liver rises.
b. Citrulline is formed from ornithine and arginine
c. Argininosuccinate is formed from citrulline and succinyl CoA
d. Over 7 molecules of ATP are used in each round of the urea cycle
e. Arginase cleaves arginine to ornithine and urea.
e. Arginase cleaves arginine to ornithine and urea.
Which compound links the urea cycle and TCA cycle?
a. oxaloacetate
b. acetyl CoA
c. pyruvate
d. citrulline
e. fumarate
e. fumarate
Which of the following sets of amino acids are made up entirely of essential amino acids?
a. glutamate, glutamine, valine
b. valine, lysine, leucine
c. Methionine, alanine, glutamate
d. Serine, tyrosine, asparagines
e. Lysine, serine, proline
b. valine, lysine, leucine
Which of the following is NOT a product of amino acid catabolism?
a. acetoacetate
b. oxaloacetate
c. acetone
d. pyruvate
e. alpha-ketoglutarate
c. acetone
Which of the following sets of amino acids are both glucogenic and ketogenic?
a. isoleucine, phenylalanine, tryrosine, tryptophan
b. glutamine, glutamate, histidine, proline
c. lysine, glutamine, serine, glutamine
d. isoleucine, methionine, glutamine, serine
a. isoleucine, phenylalanine, tryrosine, tryptophan
Uric acid is the breakdown product of
a. inosine
b. uridine
c. dUMP
d. amino acids
e. thymidine
a. inosine
Pyrimidine analogs used to treat human diseases include all of the following except
a. 5-fluorouracil for solid tumors
b. Cytosine arabinoside for myeloid leukemia
c. AZT for acquired immunodeficiency syndrome (AIDS)
d. Acyloganosine (acyclovir) for herpes simplex virus
d. Acyloganosine (acyclovir) for herpes simplex virus
Purine biosynthesis
a. purines are assembled on ribose phosphate
b. includes the thymidylate synthesis reaction
c. takes place on a sequential pathway
d. requires glutamate, aspartate, and ATP
e. has a form of regulation at every step of synthesis
a. purines are assembled on ribose phosphate
PRPP is the key molecule in
1. de novo synthesis of purine and pyrimidine nucleotides
2. salvage of purine bases
3. salvage of pyrimidine bases
4. synthesis of NAD+

a. 1, 2, and 3
b. 1 and 3
c. 2 and 4
d. 1 only
e. All of the above
e. All of the above
Inhibits formation of malonyl CoA
A. Palmitate
B. malonyl-CoA
C. linoleic acid
D. sphingomyelin
E. nervonic acid
A. Palmitate
Inhibits formation of fatty acyl-CoA into the mitchondria
A. Palmitate
B. malonyl-CoA
C. linoleic acid
D. sphingomyelin
E. nervonic acid
B. malonyl-CoA
An essential fatty acid
A. Palmitate
B. malonyl-CoA
C. linoleic acid
D. sphingomyelin
E. nervonic acid
C. linoleic acid
Activates formation of malonyl CoA
A. Palmitate
B. malonyl-CoA
C. linoleic acid
D. sphingomyelin
E. nervonic acid
D. sphingomyelin
Forms by condensation of two molecules of phosphatidylglycerol
a. sphingomyelin
b. phosphatidylserine
c. ganglioside
d. cardiolipin
d. cardiolipin
Important structural lipid of nerve cell membranes that is a phospholipids and a sphingolipid
a. sphingomyelin
b. phosphatidylserine
c. ganglioside
d. cardiolipin
a. sphingomyelin
One of the most abundant phospholipids in human tissue
a. sphingomyelin
b. phosphatidylserine
c. ganglioside
d. cardiolipin
b. phosphatidylserine
Sialic acid containing sphingolipid
a. sphingomyelin
b. phosphatidylserine
c. ganglioside
d. cardiolipin
c. ganglioside
Niemann-Pick disease is caused by the enzyme being defective or deficient in
A. tyrosinase
B. Phenylalanine hydroxylase
C. sphingomyelinase
D. galactosidase
C. sphingomyelinase
Albinism is caused by the enzyme being defective or deficient in
A. tyrosinase
B. Phenylalanine hydroxylase
C. sphingomyelinase
D. galactosidase
A. tyrosinase
Fabry’s disease is caused by the enzyme being defective or deficient in
A. tyrosinase
B. Phenylalanine hydroxylase
C. sphingomyelinase
D. galactosidase
D. galactosidase
Phenylketonuria is caused by the enzyme being defective or deficient in
A. tyrosinase
B. Phenylalanine hydroxylase
C. sphingomyelinase
D. galactosidase
B. Phenylalanine hydroxylase
Know how to identify the structures of
A. PGA1
B. Bile salt
C. Phosphatidylcholine
D. Cholesterol ester
E. S-adenoylmethionine
Know how to identify the structures of
A. serine
B. urea
C. Adenosine
D. Guanosine
E. S-adenoylmethionine
Uric acid is present in high levels in the blood in the disorder known as Gout.
A. True
B. False
A. True
The enzyme xanthine oxidoreductase catalyzes two conversions in purine degradation.
A. True
B. False
A. True
Pyrimidine degradation yields carbon dioxide, ammonia, beta-alanine and beta-aminoisobutyrate.
A. True
B. False
A. True
42. All deoyribonucleotides are synthesized from ribonucleotides by the enzyme ribonucleotide reductase.
A. True
B. False
A. True
Amino acids in excess of the biosynthetic needs of the cell are rapidly degraded.
A. True
B. False
A. True
Transamination reactions are irreversible.
A. True
B. False
B. False
are reversible.
Glutamate dehydrogenase is regulated allosterically by purine nucleotides.
A. True
B. False
A. True
Methionine is synthesized from homocysteine by transfer of a methyl group by SAM.
A. True
B. False
B. False
by methyl-THF.
Transport of ammonia to the liver is mostly in the form of glutamine and free ammonia.
A. True
B. False
B. False
and alanine.
Phospholipase A1 and A2 have no role in phospholipids synthesis.
A. True
B. False
B. False
have a role.
49. The synthesis of prostaglandins can be inhibited by steroids and non-steroidal anti-inflammatory drugs.
A. True
B. False
A. True
Dipalmitoylphosphatidylcholine (DPCC) is the major component of surfactant in the lungs.
A. True
B. False
A. True