BIOL/MBBE 402 Cumulative Multiple Choice

Which of the following is not an intermediate of the citric acid cycle? A) Acetyl-coA B) Citrate C) Oxaloacetate D) Succinyl-coA E) a-Ketoglutarate

A) Acetyl-coA

Which one of the following types of mechanisms is not known to play a role in the reversible alteration of enzyme activity? A) Activation by cleavage of an inactive zymogen B) Allosteric response to a regulatory molecule C) Alteration of the synthesis or degradation rate of an enzyme D) Covalent modification of the enzyme E) Interactions between catalytic and regulatory subunits

A) Activation by cleavage of an inactive zymogen

Which of the following is not true of the citric acid cycle? A) All enzymes of the cycle are located in the cytoplasm, except succinate dehydrogenase, which is bound to the inner mitochondrial membrane B) In the presence of malonate, one would expect succinate to accumulate C) Oxaloacetate is used as a substrate but is not consumed in the cycle D) Succinate dehydrogenase channels electrons directly into the electron transfer chain E) The condensing enzyme is subject to allosteric regulation by ATP and NADH

A) All enzymes of the cycle are located in the cytoplasm, except succinate dehydrogenase, which is bound to the inner mitochondrial membrane

For the reaction A→B, ΔG'° = -60 kJ/mol. The reaction is started with 10 mmol of A; no B is initially present. After 24 hours, analysis reveals the presence of 2 mmol of B, 8 mmol of A. Which is the most likely explanation? A) B formation is kinetically slow; equilibrium has not been reached by 24 hours B) Formation of B is thermodynamically unfavorable C) A and B have reached equilibrium concentrations D) An enzyme has shifted the equilibrium toward A E) The result described is impossible, given the fact that ΔG'° is -60 kJ/mol

A) B formation is kinetically slow; equilibrium has not been reached by 24 hours

Glucose, labeled with 14C in different carbon atoms, is added to a crude extract of a tissue rich in the enzymes of the pentose phosphate pathway. The most rapid production of 14CO2 will occur when the glucose is labeled in: A) C-1 B) C-3 C) C-4 D) C-5 E) C-6

A) C-1

Which of the following intermediates of the citric acid cycle is prochiral? A) Citrate B) Isocitrate C) Malate D) Oxaloacetate E) Succinate

A) Citrate

Which of the following statements about the chemiosmotic theory is correct? A) Electron transfer in mitochondria is accompanied by an asymmetric release of protons on oneside of the inner mitochondrial membrane B) It predicts that oxidative phosphorylation can occur even in the absence of an intact inner mitochondrial membrance C) The effect of uncoupling reagents is a consequence of their ability to carry electrons through membranes D) The membrane ATP synthase has no significant role in the chemiosmotic theory E) All of the above are correct

A) Electron transfer in mitochondria is accompanied by an asymmetric release of protons on oneside of the inner mitochondrial membrane

In the digestion of protein that occurs in the small intestine, which enzyme is critical in the activation of zymogens? A) Enteropeptidase B) Hexokinase C) Papain D) Pepsin E) Secretin

A) Enteropeptidase

Which of the following is not true of the reaction catalyzed by glutamate dehydrogenase? A) It is similar to transamination in that it involves the coenzyme pyridoxal phosphate (PLP) B) NH4+ is produced C) The enzyme can use either NAD+ or NADP+ as a cofactor D) The enzyme is glutamate-specific, but the reaction is involved in oxidizing other amino acids E) alpha-Ketoglutarate is produced from an amino acid

A) It is similar to transamination in that it involves the coenzyme pyridoxal phosphate (PLP)

Which of these cofactors participates directly in most of the oxidation-reduction reactions in the fermentation of glucose to lactate? A) NAD+/NADH B) ADP C) ATP D) FAD/FADH2 E) Glyceraldehyde 3-phosphate

A) NAD+/NADH

Fatty acids are activated to acyl-CoAs and the acyl group is further transferred to carnitine because: A) acyl-carnitines readily cross the mitochondrial inner membrane, but acyl-CoAs do not B) acyl-CoAs easily cross the mitochondrial membrane, but the fatty acids themselves will not C) carnitine is required to oxidize NAD+ to NADH D) fatty acids cannot be oxidized by FAD unless they are in the acyl-carnitine form E) None of the above is true

A) acyl-carnitines readily cross the mitochondrial inner membrane, but acyl-CoAs do not

2,4-Dinitrophenol and oligomycin inhibit mitochondrial oxidative phosphorylation. 2,4- Dinitrophenol is an uncoupling agent; oligomycin blocks the ATP synthesis reaction itself. Therefore, 2,4-dinitrophenol will: A) allow electron transfer in the presence of oligomycin B) allow oxidative phosphorylation in the presence of oligomycin C) block electron transfer in the presence of oligomycin D) diminish O2 consumption in the presence of oligomycin E) do none of the above

A) allow electron transfer in the presence of oligomycin

During seed germination, the glyoxylate pathway is important to plants because it enables them to: A) carry out the net synthesis of glucose from acetyl-CoA B) form acetyl-CoA from malate C) get rid of isocitrate formed from the aconitase reaction D) obtain glyoxylate for cholesterol biosynthesis E) obtain glyoxylate for pyrimidine synthesis

A) carry out the net synthesis of glucose from acetyl-CoA

In the reoxidation of QH2 by purified ubiquinone-cytochrome c reductase (Complex III) from heart muscle, the overall stoichiometry of the reaction requires 2 mol of cytochrome c per mole of QH2 because: A) cytochrome c is a one-electron acceptor, whereas QH2 is a two-electron donor B) cytochrome c is a two-electron acceptor, whereas QH2 is a one-electron donor C) cytochrome c is water soluble and operates between the inner and outer mitochondrial membranes D) heart muscle has a high rate of oxidative metabolism, and therefore requires twice as much cytochrome c as QH2 for electron transfer to proceed normally E) two molecules of cytochrome c must first combine physically before they are catalytically active

A) cytochrome c is a one-electron acceptor, whereas QH2 is a two-electron donor

The first reaction in glycolysis that results in the formation of an energy-rich compound (i.e., acompound whose hydrolysis has a highly negative ΔG'°) is catalyzed by: A) glyceraldehyde 3-phosphate dehydrogenase B) hexokinase C) phosphofructokinase-1 D) phosphoglycerate kinase E) triose phosphate isomerase

A) glyceraldehyde 3-phosphate dehydrogenase

Lipoprotein lipase acts in: A) hydrolysis of triacylglycerols of plasma lipoproteins to supply fatty acids to various tissues B) intestinal uptake of dietary fat C) intracellular lipid breakdown of lipoproteins D) lipoprotein breakdown to supply needed amino acids E) none of the above

A) hydrolysis of triacylglycerols of plasma lipoproteins to supply fatty acids to various tissues

Upon the addition of 2,4-dinitrophenol (DNP) to a suspension of mitochondria carrying out oxidative phosphorylation linked to the oxidation of malate, all of the following occur except: A) oxygen consumption decreases B) oxygen consumption increases C) the P/O ratio drops from a value of approximately 2.5 to 0 D) the proton gradient dissipates E) the rate of transport of electrons from NADH to O2 becomes maximal

A) oxygen consumption decreases

Anaplerotic reactions . A) produce oxaloacetate and malate to maintain constant levels of citric acid cycle intermediates B) produce biotin needed by pyruvate carboxylase C) recycle pantothenate used to make CoA D) produce pyruvate and citrate to maintain constant levels of citric acid cycle intermediates E) all of the above

A) produce oxaloacetate and malate to maintain constant levels of citric acid cycle intermediates

The main function of the oxidative phase of pentose phosphate pathway is to: A) supply pentoses and NADPH B) give the cell an alternative pathway should glycolysis fail C) provide a mechanism for the utilization of the carbon skeletons of excess amino acids D) supply energy E) supply NADH

A) supply pentoses and NADPH

Oxaloacetate uniformly labeled with 14C (i.e., with equal amounts of 14C in each of its carbon atoms) is condensed with unlabeled acetyl-CoA. After a single pass through the citric acid cycle back to oxaloacetate, what fraction of the original radioactivity will be found in the oxaloacetate? A) all B) 1/2 C) 1/3 D) 1/4 E) 3/4

B) 1/2

An enzyme used in both glycolysis and gluconeogenesis is: A) glucose 6-phosphatase B) 3-phosphoglycerate kinase C) hexokinase D) phosphofructokinase-1 E) pyruvate kinase

B) 3-phosphoglycerate kinase

Which of these directly donates a nitrogen atom for the formation of urea during the urea cycle? A) Adenine B) Aspartate C) Creatine D) Glutamate E) Ornithine

B) Aspartate

Cyanide, oligomycin, and 2,4-dinitrophenol (DNP) are inhibitors of mitochondrial aerobic phosphorylation. Which of the following statements correctly describes the mode of action of the three inhibitors? A) Cyanide and 2,4-dinitrophenol inhibit the respiratory chain, and oligomycin inhibits the synthesis of ATP B) Cyanide inhibits the respiratory chain, whereas oligomycin and 2,4-dinitrophenol inhibit the synthesis of ATP C) Cyanide, oligomycin, and 2,4-dinitrophenol compete with O2 for cytochrome oxidase (Complex IV) D) Oligomycin and cyanide inhibit synthesis of ATP; 2,4-dinitrophenol inhibits the respiratory chain E) Oligomycin inhibits the respiratory chain, whereas cyanide and 2,4-dinitrophenol prevent the synthesis of ATP

B) Cyanide inhibits the respiratory chain, whereas oligomycin and 2,4-dinitrophenol inhibit the synthesis of ATP

Malonate is a competitive inhibitor of succinate dehydrogenase. If malonate is added to a mitochondrial preparation that is oxidizing pyruvate as a substrate, which of the following compounds would you expect to decrease in concentration? A) Citrate B) Fumarate C) Isocitrate D) Pyruvate E) Succinate

B) Fumarate

Which enzyme is the major regulatory control point for β-oxidation? A) pyruvate carboxylase B) carnitine acyl transferase I C) acetyl CoA dehydrogenase D) enoyl CoA isomerase E) methylmalonyl CoA mutase

B) carnitine acyl transferase I

Free fatty acids in the bloodstream are: A) bound to hemoglobin B) carried by the protein serum albumin C) freely soluble in the aqueous phase of the blood D) nonexistent; the blood does not contain free fatty acids E) present at levels that are independent of epinephrine

B) carried by the protein serum albumin

Muscle contraction involves the conversion of: A) chemical energy to potential energy B) chemical energy to kinetic energy C) kinetic energy to chemical energy D) potential energy to chemical energy E) potential energy to kinetic energy

B) chemical energy to kinetic energy

The two main purposes of the citric acid cycle are A) synthesis of citrate and gluconeogenesis B) degradation of acetyl-CoA to produce energy and to supply precursors for anabolism C) degradation of pyruvate to produce energy and to supply precursors for anabolism D) degradation of glucose to produce energy and to supply precursors for anabolism E) degradation of pyruvate to produce energy and to synthesize oxaloacetate for gluconeogenesis

B) degradation of acetyl-CoA to produce energy and to supply precursors for anabolism

Aside from maintaining the integrity of its hereditary material, the most important general metabolic concern of a cell is: A) keeping its glucose levels high B) maintaining a constant supply and concentration of ATP C) preserving its ability to carry out oxidative phosphorylation D) protecting its enzymes from rapid degradation E) running all its major metabolic pathways at maximum efficiency

B) maintaining a constant supply and concentration of ATP

Mammals produce heat by using the endogenous uncoupling agent: A) the small molecule 2-4-Dinitrophenol synthesized by the cell B) the protein thermogenin C) the protein thioredoxin D) the protein cytochrome c E) a modified form of the FoF1 ATPase

B) the protein thermogenin

If the 18-carbon saturated fatty acid, stearic acid is oxidized completely to carbon dioxide and water (via the β-oxidation pathway and the citric acid cycle), and all of the energy-conserving products are used to drive ATP synthesis in the mitochondrion, the net yield of ATP per molecule of stearic acid is (FADH2 equals to 1.5 ATP, NADH equals to 2.5 ATP): A) 3 B) 10 C) 122 D) 108 E) 1,000

C) 122

Inorganic fluoride inhibits enolase. In an anaerobic system that is metabolizing glucose as a substrate, which of the following compounds would you expect to increase in concentration following the addition of fluoride? A) Glucose B) Glyoxylate C) 2-phosphoglycerate D) Phosphoenolpyruvate E) Pyruvate

C) 2-phosphoglycerate

What is the correct order of function of the following enzymes of β-oxidation? 1. β-Hydroxyacyl-CoA dehydrogenase 2. Thiolase 3. Enoyl-CoA hydratase 4. Acyl-CoA dehydrogenase A) 1, 2, 3, 4 B) 3, 1, 4, 2 C) 4, 3, 1, 2 D) 1, 4, 3, 2 E) 4, 2, 3, 1

C) 4, 3, 1, 2

The standard reduction potentials (E'°) for the following half reactions are given. Fumarate + 2H+ + 2e- → succinate E'° = +0.031 V FAD + 2H+ + 2e-→FADH2 E'° = -0.219 V If you mixed succinate, fumarate, FAD, and FADH2 together, all at l M concentrations and in the presence of succinate dehydrogenase, which of the following would happen initially? A) Fumarate and succinate would become oxidized; FAD and FADH2 would become reduced B) No reaction would occur because all reactants and products are already at their standard concentrations C) Fumarate would become reduced, FADH2 would become oxidized D) Succinate would become oxidized, FAD would become reduced E) Succinate would become oxidized, FADH2 would be unchanged because it is a cofactor

C) Fumarate would become reduced, FADH2 would become oxidized

Which of the following statements about the pentose phosphate pathway is correct? A) It generates 36 mol of ATP per mole of glucose consumed B) It generates 6 moles of CO2 for each mole of glucose consumed C) It provides precursors for the synthesis of nucleotides D) It is a reductive pathway; it consumes NADH E) It is present in plants, but not in animals

C) It provides precursors for the synthesis of nucleotides

Ketone bodies are formed in the liver and transported to the extrahepatic tissues mainly as: A) acetoacetyl-CoA B) acetone C) beta-hydroxybutyric acid D) beta-hydroxybutyryl-CoA E) lactic acid

C) beta-hydroxybutyric acid

The isomerization of citrate to isocitrate: A) is the only unnecessary step of the citric acid cycle B) protects cells from the toxic effects of arsenite ion C) converts a tertiary alcohol, which cannot easily be oxidized, to a secondary alcohol that can be oxidized D) is a major regulatory step for the citric acid cycle E) is an oxidation reaction

C) converts a tertiary alcohol, which cannot easily be oxidized, to a secondary alcohol that can

The glycerol produced from the hydrolysis of triacylglycerides enters glycolysis as: A) glucose B) glucose-6-phosphate C) dihydroxyacetone phosphate D) pyruvate E) glyceryl CoA

C) dihydroxyacetone phosphate

ne is: A) a 15-carbon fatty acid B) an essential cofactor for the citric acid cycle C) essential for intracellular transport of fatty acids D) one of the amino acids commonly found in protein E) present only in carnivorous animals

C) essential for intracellular transport of fatty acids

The human genetic disease phenylketonuria (PKU) can result from: A) deficiency of protein in the diet B) inability to catabolize ketone bodies C) inability to convert phenylalanine to tyrosine D) inability to synthesize phenylalanine E) production of enzymes containing no phenylalanine

C) inability to convert phenylalanine to tyrosine

During oxidative phosphorylation, the proton motive force that is generated by electron transport is used to: A) create a pore in the inner mitochondrial membrane B) generate the substrates (ADP and Pi) for the ATP synthase C) induce a conformational change in the ATP synthase D) oxidize NADH to NAD+ E) reduce O2 to H2O

C) induce a conformational change in the ATP synthase

Glutamate is metabolically converted to -ketoglutarate and NH4+ by a process described as: A) deamination B) hydrolysis C) oxidative deamination D) reductive deamination E) transamination

C) oxidative deamination

14. Gluconeogenesis must use "bypass reactions" to circumvent three reactions in the glycolyticpathway that are highly exergonic and essentially irreversible. Reactions carried out by which three of the enzymes listed must be bypassed in the gluconeogenic pathway? 1) Hexokinase 2) Phosphoglycerate kinase 3) Phosphofructokinase-1 4) Pyruvate kinase 5) Triosephosphate isomerase A) 1, 2, 3 B) 1, 2, 4 C) 1, 4, 5 D) 1, 3, 4 E) 2, 3, 4

D) 1, 3, 4

The conversion of 1 mol of fructose 1,6-bisphosphate to 2 mol of phosphoenolpyruvate by the glycolytic pathway results in a net formation of: A) 1 mol of NAD+ and 2 mol of ATP B) 1 mol of NADH and 1 mol of ATP C) 2 mol of NADH and 4 mol of ATP D) 2 mol of NADH and 2 mol of ATP E) 4 mol of NADH and 2 mol of ATP

D) 2 mol of NADH and 2 mol of ATP

Which of the following is (are) true of the β-oxidation of long-chain fatty acids? 1. The enzyme complex that catalyzes the reaction contains biotin. 2. FADH2 serves as an electron carrier. 3. NADH serves as an electron carrier. 4. Oxidation of an 18-carbon fatty acid produces six molecules of propionyl-CoA. 5. Oxidation of a 15-carbon fatty acid produces at least one propionyl-CoA. A) 1, 2, and 3 B) 1, 2, and 5 C) 2, 3, and 4 D) 2, 3, and 5 E) 3 and 5 only

D) 2, 3, and 5

The conversion of 1 mol of pyruvate to 3 mol of CO2 via pyruvate dehydrogenase and the citric acid cycle also yields _____ mol of NADH, _____ mol of FADH2, and _____ mol of ATP (or GTP). A) 2; 2; 2 B) 3; 1; 1 C) 3; 2; 0 D) 4; 1; 1 E) 4; 2; 1

D) 4; 1; 1

During β-oxidation of fatty acids, ___________ is produced in peroxisomes but not in mitochondria. A) acetyl-CoA B) FADH2 C) H2O D) H2O2 E) NADH

D) H2O2

β-oxidation of fatty acid is promoted by which of the following? A) ATP B) FADH2 C) acetyl-CoA D) NAD+ E) propionyl-CoA

D) NAD+

Glucose labeled with 14C in C-3 and C-4 is completely converted to acetyl-CoA via glycolysis and the pyruvate dehydrogenase complex. What percentage of the acetyl-CoA molecules formed will be labeled with 14C, and in which position of the acetyl moiety will the 14C label be found? A) 100% of the acetyl-CoA will be labeled at C-1 (carboxyl) B) 100% of the acetyl-CoA will be labeled at C-2 C) 50% of the acetyl-CoA will be labeled, all at C-2 (methyl) D) No label will be found in the acetyl-CoA molecules E) Not enough information is given to answer this question

D) No label will be found in the acetyl-CoA molecules

Which of the following statements concerning the β-oxidation of fatty acids is true? A) About 1,200 ATP molecules are ultimately produced per 20-carbon fatty acid oxidized B) One FADH2 and two NADH are produced for each acetyl-CoA C) The free fatty acid must be carboxylated in the β position by a biotin-dependent reaction before the process of β oxidation commences D) The free fatty acid must be converted to a thioester before the process of β oxidation commences E) Two NADH are produced for each acetyl-CoA

D) The free fatty acid must be converted to a thioester before the process of β oxidation commences

The major site of formation of acetoacetate from fatty acids is the: A) adipose tissue B) intestinal mucosa C) kidney D) liver E) muscle

D) liver

Tetrahydrofolate (THF) and its derivatives shuttle between different substrates. A) electrons B) H+ C) acyl groups D) one carbon units E) NH2 groups

D) one carbon units

In an anaerobic muscle preparation, lactate formed from glucose labeled in C-3 and C-4 would be labeled in: A) all three carbon atoms B) only the carbon atom carrying the OH C) only the methyl carbon atom D) only the carboxyl carbon atom E) the methyl and carboxyl carbon atoms

D) only the carboxyl carbon atom

The steps of glycolysis between glyceraldehyde 3-phosphate and 3-phosphoglycerate involve all of the following except: A) ATP synthesis B) catalysis by phosphoglycerate kinase C) the formation of 1,3-bisphosphoglycerate D) oxidation of NADH to NAD+ E) utilization of Pi

D) oxidation of NADH to NAD+

All of the oxidative steps of the citric acid cycle are linked to the reduction of NAD+ exceptthe reaction catalyzed by: A) isocitrate dehydrogenase B) malate dehydrogenase C) pyruvate dehydrogenase D) succinate dehydrogenase E) the a-ketoglutarate dehydrogenase complex

D) succinate dehydrogenase

The carbon atoms from a fatty acid with an odd number of carbons will enter the citric acid cycle as acetyl-CoA and: A) butyrate B) citrate C) malate D) succinyl-CoA E) α-ketoglutarate

D) succinyl-CoA

The hydrolysis of phosphoenolpyruvate proceeds with a ΔG'° of about -62 kJ/mol. The greatest contributing factors to this reaction are the destabilization of the reactants by electostatic repulsion and stabilization of the product pyruvate by: A) electrostatic attraction B) ionization C) polarization D) tautomerization E) resonance

D) tautomerization

Entry of acetyl-CoA into the citric acid cycle is decreased when: A) [AMP] is high B) NADH is rapidly oxidized through the respiratory chain C) the ratio of [ATP]/[ADP is low D) the ratio of [ATP]/[ADP] is high E) the ratio of [NAD+]/[NADH] is high

D) the ratio of [ATP]/[ADP] is high

Biological oxidation-reduction reactions always involve: A) direct participation of oxygen B) formation of water C) mitochondria D) transfer of electron(s) E) transfer of hydrogens

D) transfer of electron(s)

Glucose labeled with 14C in C-1 and C-4 gives rise in glycolysis to pyruvate labeled in: A) its methyl carbon B) all three carbons C) its carbonyl carbon D) its carboxyl carbon E) A and D

E) A and D

Citrate synthase and the NAD+-specific isocitrate dehydrogenase are two key regulatory enzymes of the citric acid cycle. These enzymes are inhibited by: A) acetyl-CoA and fructose 6-phosphate B) AMP and/or NAD+ C) AMP and/or NADH D) ATP and/or NAD+ E) ATP and/or NADH

E) ATP and/or NADH

In normal mitochondria, the rate of NADH consumption (oxidation) will: A) be increased in active muscle, decreased in inactive muscle B) be very low if the ATP synthase is inhibited, but increase when an uncoupler is added C) decrease if mitochondrial ADP is depleted D) decrease when cyanide is used to prevent electron transfer through the cytochrome a + a3 complex E) All of the above are true

E) All of the above are true

Which compound is an intermediate of the β-oxidation of fatty acids? A) CH3—(CH2)20—CO—COOH B) CH3—CH2—CO—CH2—CO—OPO2-3 C) CH3—CH2—CO—CH2—OH D) CH3—CH2—CO—CO—S—CoA E) CH3—CO—CH2—CO—S—CoA

E) CH3—CO—CH2—CO—S—CoA

Which one of the following is not associated with the oxidation of substrates by the citric acid cycle? A) All of the below are involved. B) CO2 production C) Flavin reduction D) Lipoic acid present in some of the enzyme systems E) Pyridine nucleotide oxidation

E) Pyridine nucleotide oxidation

Which combination of cofactors is involved in the conversion of pyruvate to acetyl-CoA? A) Biotin, FAD, and TPP B) Biotin, NAD+, and FAD C) NAD+, biotin, and TPP D) Pyridoxal phosphate, FAD, and lipoic acid E) TPP, lipoic acid, and NAD+

E) TPP, lipoic acid, and NAD+

Which of the following statements is false in reference to the mammalian synthesis of urea? A) Krebs was a major contributor to the elucidation of the pathway involved B) The amino acid arginine is the immediate precursor to urea C) The carbon atom of urea is derived from mitochondrial HCO3- D) The precursor to one of the nitrogens of urea is aspartate E) The process of urea production is an energy-yielding series of reactions

E) The process of urea production is an energy-yielding series of reactions

Which of the following statements is incorrect? A) Aerobically, oxidative decarboxylation of pyruvate forms acetate that enters the citric acid cycle B) In anaerobic muscle, pyruvate is converted to lactate C) In yeast growing anaerobically, pyruvate is converted to ethanol D) Reduction of pyruvate to lactate regenerates a cofactor essential for glycolysis E) Under anaerobic conditions pyruvate does not form because glycolysis does not occur

E) Under anaerobic conditions pyruvate does not form because glycolysis does not occur

If a person's urine contains unusually high concentrations of urea, which one of the following diets has he or she probably been eating recently? A) High carbohydrate, very low protein B) Very high carbohydrate, no protein, no fat C) Very very high fat, high carbohydrate, no protein D) Very high fat, very low protein E) Very low carbohydrate, very high protein

E) Very low carbohydrate, very high protein

Which one of the following enzymatic activities would be decreased by thiamine deficiency? A) Fumarase B) Isocitrate dehydrogenase C) Malate dehydrogenase D) Succinate dehydrogenase E) a-Ketoglutarate dehydrogenase complex

E) a-Ketoglutarate dehydrogenase complex

The reaction of the citric acid cycle that is most similar to the pyruvate dehydrogenase complex-catalyzed conversion of pyruvate to acetyl-CoA is the conversion of: A) citrate to isocitrate B) fumarate to malate C) malate to oxaloacetate D) succinyl-CoA to succinate E) a-ketoglutarate to succinyl-CoA

E) a-ketoglutarate to succinyl-CoA

Intermediates in the citric acid cycle are used as precursors in the biosynthesis of: A) amino acids B) nucleotides C) fatty acids D) sterols E) all of the above

E) all of the above

A function of the glyoxylate cycle, in conjunction with the citric acid cycle, is to accomplish the: A) complete oxidation of acetyl-CoA to CO2 plus reduced coenzymes B) net conversion of lipid to carbohydrate C) net synthesis of four-carbon dicarboxylic acids from acetyl-CoA D) net synthesis of long-chain fatty acids from citric acid cycle intermediates E) both B and C are correct

E) both B and C are correct

Glucose breakdown in certain mammalian and bacterial cells can occur by mechanisms other than classic glycolysis. In most of these, glucose 6-phosphate is oxidized to 6-phosphogluconate, which is then further metabolized by: A) an aldolase-type split to form glyceric acid and glyceraldehyde 3-phosphate B) an aldolase-type split to form glycolic acid and erythrose 4-phosphate C) conversion to 1,6-bisphosphogluconate D) oxidation to a six-carbon dicarboxylic acid E) decarboxylation to produce keto- and aldopentoses

E) decarboxylation to produce keto- and aldopentoses

Biological oxidation-reduction reactions never involve: A) transfer of e- from one molecule to another B) transfer of H+ (or H3O+) from one molecule to another C) formation of free H+ (or H3O+) D) none of the above E) formation of free e-

E) formation of free e-

In comparison with the resting state, actively contracting human muscle tissue has a: A) higher concentration of ATP B) lower consumption of glucose C) lower rate of consumption of oxygen D) lower ratio of NADH to NAD+ E) higher rate of lactate formation

E) higher rate of lactate formation

The citric acid cycle is an oxidative pathway requiring oxygen for operation. The enzyme which consumes oxygen during the operation of the cycle is? A) isocitrate dehydrogenase B) a-Ketoglutarate dehydrogenase C) aconitase D) succinate dehydrogenase E) none of the above

E) none of the above

All of the following enzymes involved in the flow of carbon from glucose to lactate (glycolysis) are also involved in the reversal of this flow (gluconeogenesis) except: A) 3-phosphoglycerate kinase B) aldolase C) enolase D) phosphoglucoisomerase E) phosphofructokinase-1

E) phosphofructokinase-1

The following fatty acid, in which the indicated carbon is labeled with 14C, is fed to an animal: 14CH3(CH2)9COOH After allowing 30 minutes for fatty acid β-oxidation, the label would most likely be recovered in: A) acetyl-CoA B) beta-hydroxy butyryl-CoA C) both acetyl-CoA and propionyl-CoA D) palmitoyl-CoA E) propionyl-CoA

E) propionyl-CoA

The reaction of the citric acid cycle that produces an ATP equivalent (in the form of GTP) by substrate level phosphorylation is the conversion of: A) citrate to isocitrate B) fumarate to malate C) malate to oxaloacetate D) succinate to fumarate E) succinyl-CoA to succinate

E) succinyl-CoA to succinate

In amino acid catabolism, the first reaction for many amino acids is a(n): A) decarboxylation requiring thiamine pyrophosphate (TPP) B) hydroxylation requiring NADPH and O2 C) oxidative deamination requiring NAD+ D) reduction requiring pyridoxal phosphate (PLP) E) transamination requiring pyridoxal phosphate (PLP)

E) transamination requiring pyridoxal phosphate (PLP)

The two moles of CO2 produced in the first turn of the citric acid cycle have their origin in the: A) carboxyl and methylene carbons of oxaloacetate B) carboxyl group of acetate and a carboxyl group of oxaloacetate C) carboxyl group of acetate and the keto group of oxaloacetate D) two carbon atoms of acetate E) two carboxyl groups derived from oxaloacetate

E) two carboxyl groups derived from oxaloacetate

Almost all of the oxygen (O2) one consumes in breathing is converted to: A) acetyl-CoA B) carbon dioxide (CO2) C) carbon monoxide and then to carbon dioxide D) none of the above E) water

E) water

Compare the two reaction coordinate diagrams below and select the answer that correctly describes their relationship. In each case, the single intermediate is the ES complex. a. (a) describes a strict "lock and key" model, whereas (b) describes a transition-state complementarity model b. The activation energy for the catalyzed reaction is #5 in (a) and is #7 in (b) c. The activation energy for the uncatalyzed reaction is given by #5 + #6 in (a), and by #7 + #4 in (b) d. The contribution of binding energy is given by #5 in (a) and by #7 in (b) e. The ES complex is given by #2 in (a) and #3 in (b)

a. (a) describes a strict "lock and key" model, whereas (b) describes a transition-state complementarity model

Which of these statements is generally true of integral membrane proteins? a. A hydropathy plot reveals one or more regions with a high hydropathy index b. The domains that protrude on the cytoplasmic face of the plasma membrane nearly always have covalently attached oligosaccharides c. They are unusually susceptible to degradation by trypsin d. They can be removed from the membrane with high salt or mild denaturing agents e. They undergo constant rotational motion that moves a given domain from the outer face of a membrane to the inner face and then back to the outer

a. A hydropathy plot reveals one or more regions with a high hydropathy index

Which of these statements about facilitated diffusion across a membrane is true? a. A specific membrane protein lowers the activation energy for movement of the solute through the membrane b. It can increase the size of a transmembrane concentration gradient of the diffusing solute. c. It is impeded by the solubility of the transported solute in the nonpolar interior of the lipid bilayer d. It is responsible for the transport of gases such as O2, N2, and CH4across biological membranes e. The rate is not saturable by the transported substrate

a. A specific membrane protein lowers the activation energy for movement of the solute through the membrane

Which of the following best describes the cholesterol molecule? a. Amphipathic b. Nonpolar, charged c. Nonpolar, uncharged d. Polar, charged e. Polar, uncharged

a. Amphipathic

From the abbreviated name of the compound Gal(β1-4)Glc, we know that: a. C-4 of glucose is joined to C-1 of galactose by a glycosidic bond b. the compound is a D-enantiomer c. the galactose residue is at the reducing end d. the glucose is in its pyranose form e. the glucose residue is the α-anomer

a. C-4 of glucose is joined to C-1 of galactose by a glycosidic bond

6. The three-dimensional structure of macromolecules is formed and maintained primarily through non-covalent interactions. Which one of the following is not considered a non-covalent interaction? a. Carbon-carbon bonds b. Hydrogen bonds c. Hydrophobic interactions d. Ionic interactions e. Van der Waals interactions

a. Carbon-carbon bonds

Which of the following statements is false? a. Collagen is a protein in which the polypeptides are mainly in the a-helix conformation. b. Disulfide linkages are important for keratin structure. c. Gly residues are particularly abundant in collagen. d. Silk fibroin is a protein in which the polypeptide is almost entirely in the b conformation. e. a-keratin is a protein in which the polypeptides are mainly in the a-helix conformation.

a. Collagen is a protein in which the polypeptides are mainly in the a-helix conformation.

Which of the following statements about cystine is correct? a. Cystine forms when the —CH₂—SH R group is oxidized to form a —CH₂—S—S—CH₂— disulfide bridge between two cysteines. b. Cystine is an example of a nonstandard amino acid, derived by linking two standard amino acids. c. Cystine is formed by the oxidation of the carboxylic acid group on cysteine. d. Cystine is formed through a peptide linkage between two cysteines. e. Two cystines are released when a —CH₂—S—S—CH₂— disulfide bridge is reduced to — CH₂—SH.

a. Cystine forms when the —CH2—SH R group is oxidized to form a —CH2—S—S—CH2— disulfide bridge between two cysteines.

Which of the following pairs of bonds within a peptide backbone show free rotation around both bonds? a. Cα—C and N—Cα b. C=O and N—C c. C=O and N—Cα d. N—C and Cα—C e. N—Cα and N—C

a. Cα—C and N—Cα

Which of the following has not been shown to play a role in determining the specificity of protein kinases? a. Disulfide bonds near the phosphorylation site b. Primary sequence at phosphorylation site c. Protein quaternary structure d. Protein tertiary structure e. Residues near the phosphorylation site

a. Disulfide bonds near the phosphorylation site

Which of these statements about the composition of biological membranes is false? a. In a given eukaryotic cell type (e.g., a hepatocyte), all intracellular membranes have essentially the same complement of lipids and proteins b. The carbohydrate found in membranes is virtually all part of either glycolipids or glycoproteins c. The plasma membranes of the cells of vertebrate animals contain more cholesterol than the mitochondrial membranes d. The ratio of lipid to protein varies widely among cell types in a single organism e. Triacylglycerols are not commonly found in membranes

a. In a given eukaryotic cell type (e.g., a hepatocyte), all intracellular membranes have essentially the same complement of lipids and proteins

Which of these is a general feature of the lipid bilayer in all biological membranes? a. Individual lipid molecules are free to diffuse laterally in the surface of the bilayer b. Individual lipid molecules in one face (monolayer) of the bilayer readily diffuse (flip-flop) to the other monolayer c. Polar, but uncharged, compounds readily diffuse across the bilayer d. The bilayer is stabilized by covalent bonds between neighboring phospholipid molecules e. The polar head groups face inward toward the inside of the bilayer

a. Individual lipid molecules are free to diffuse laterally in the surface of the bilayer

Which of the following statements concerning the process of spontaneous folding of proteins is false? a. It may be an essentially random process b. It may be defective in some human disease c. It may involve a gradually decreasing range of conformational species d. It may involve initial formation of a highly compact state e. It may involve initial formation of local secondary structure

a. It may be an essentially random process (double check)

Which of the following generalizations concerning motor proteins is correct? a. They convert chemical energy into kinetic energy b. They convert chemical energy into potential energy c. They convert kinetic energy into chemical energy d. They convert kinetic energy into rotational energy e. They convert potential energy into chemical energy

a. They convert chemical energy into kinetic energy

Imagine a protein that binds to several different targets with the levels of levels of affinity shown below. Receptor W: Ka = 2.0 x 10⁻⁴ M⁻¹ Receptor X: Ka = 6.7 x 10⁻⁷ M⁻¹ Receptor Y: Kd = 8.0 x 108 M Receptor Z: Kd = 1.5 x 105 M Rank the affinity of the protein for the target from strongest to weakest. a. W > Z > X > Y b. Z > X > W > Y c. W > Y > X > Z d. Y > W > X > Z e. Y > X > Z > W

a. W > Z > X > Y

In the diagram below, the plane drawn behind the peptide bond indicates the: a. absence of rotation around the C—N bond because of its partial double-bond character. b. plane of rotation around the Ca—N bond. c. region of steric hindrance determined by the large C=O group. d. region of the peptide bond that contributes to a Ramachandran plot. e. theoretical space between -180 and +180 degrees that can be occupied by the f and y angles in the peptide bond.

a. absence of rotation around the C—N bond because of its partial double-bond character.

Amino acids are ampholytes because they can function as either a(n): a. acid or a base. b. neutral molecule or an ion. c. polar or a nonpolar molecule. d. standard or a nonstandard monomer in proteins. e. transparent or a light-absorbing compound.

a. acid or a base.

The energy that is released by the hydrolysis of ATP by actin is used for: a. actin filament assembly b. actin filament disassembly c. actin-myosin assembly d. actin-myosin disassembly e. muscle contraction

a. actin filament assembly

The pH of a sample of urine is 5.7, while lime juice has a pH 2.0. The urine sample has: a. approximately a hundred thousand times lower [H+] than the lime juice b. approximately 5,000 times lower [H+] than the lime juice c. approximately 3.5 times lower [H+] than the lime juice d. approximately 0.285 times the [H+] as the lime juice e. approximately 5 times lower [H+] than the lime juice

a. approximately a hundred thousand times lower [H+] than the lime juice (double check)

Peripheral membrane proteins: a. are generally noncovalently bound to membrane lipids b. are usually denatured when released from membranes c. can be released from membranes only by treatment with detergent(s) d. may have functional units on both sides of the membrane e. penetrate deeply into the lipid bilayer

a. are generally noncovalently bound to membrane lipids

In the α-helix the hydrogen bonds: a. are roughly parallel to the axis of the helix. b. are roughly perpendicular to the axis of the helix. c. occuar mainly between electronegative atoms of the R groups. d. occur only between some of the amino acids of the helix. e. occur only near the amino and carboxyl termini of the helix.

a. are roughly parallel to the axis of the helix.

A true statement about hydrophobic interactions is that they: a. are the driving force in the formation of micelles of amphipathic compounds in water. b. do not contribute to the structure of water-soluble proteins. c. have bonding energies of approximately 20-40 Kilo joule per mole. d. involve the ability of water to denature proteins. e. primarily involve the effect of polar solutes on the entropy of aqueous systems.

a. are the driving force in the formation of micelles of amphipathic compounds in water.

In glycoproteins, the carbohydrate moiety is always attached through the amino acid residues: a. asparagine, serine, or threonine b. aspartate or glutamate c. glutamine or arginine d. glycine, alanine, or aspartate e. tryptophan, aspartate, or cysteine

a. asparagine, serine, or threonine

Sphingosine is not a component of: a. cardiolipin b. ceramide c. cerebrosides d. gangliosides e. sphingomyelin

a. cardiolipin

In a mixture of the five proteins listed below, which should elute 4th in size-exclusion (gel- filtration) chromatography? a. cytochrome c (Mr = 13,700) b. immunoglobulin G (Mr = 145,000) c. ribonuclease A (Mr = 450,000) d. RNA polymerase (Mr = 68,500) e. serum albumin (Mr = 13, 000)

a. cytochrome c (Mr = 13,700)

Enzymes are biological catalysts that enhance the rate of a reaction by: a. decreasing the activation energy b. decreasing the amount of free energy released c. increasing the activation energy d. increasing the amount of free energy released e. increasing the energy of the transition state

a. decreasing the activation energy

Hormone-activated phospholipase C can convert phosphatidylinositol 4,5-bisphosphate to: a. diacylglycerol + inositol triphosphate b. diacylglycerol + inositol+ phosphate c. glycerol + inositol + phosphate d. glycerol + phosphoserine e. phosphatidyl glycerol + inositol + phosphate

a. diacylglycerol + inositol triphosphate

The specificity of the potassium channel for K+over Na+is mainly the result of the:= a. differential interaction with the selectivity filter protein b. hydrophobicity of the channel c. phospholipid composition of the channel d. presence of carbohydrates in the channel e. presence of cholesterol in the channel

a. differential interaction with the selectivity filter protein

Proteins often have regions that show specific, coherent patterns of folding or function. These regions are called: a. domains. b. oligomers. c. peptides. d. sites. e. subunits.

a. domains.

Facilitated diffusion through a biological membrane is: a. driven by a difference of solute concentration b. driven by ATP c. endergonic d. generally irreversible e. not specific with respect to the substrate

a. driven by a difference of solute concentration

The most important contribution to the stability of a protein's conformation appears to be the: a. entropy increase from the decrease in ordered water molecules forming a solvent shell around it. b. maximum entropy increase from ionic interactions between the ionized amino acids in a protein. c. sum of free energies of formation of many weak interactions among the hundreds of amino acids in a protein. d. sum of free energies of formation of many weak interactions between its polar amino acids and surrounding water. e. stabilizing effect of hydrogen bonding between the carbonyl group of one peptide bond and the amino group of another.

a. entropy increase from the decrease in ordered water molecules forming a solvent shell around it.

The type of motion least common in biological membranes is: a. flip-flop diffusion of phospholipid from one monolayer to the other. b. lateral diffusion of individual lipid molecules within the plane of each monolayer. c. lateral diffusion of membrane proteins in the bilayer. d. lateral diffusion of protein molecules in the lipid bilayer e. random motion of the fatty acyl side chains in the interior of the phospholipid bilayer.

a. flip-flop diffusion of phospholipid from one monolayer to the other.

Phenyl-methane-sulfonyl-fluoride (PMSF) inactivates serine proteases by binding covalently to the catalytic serine residue at the active site; this enzyme-inhibitor bond is not cleaved by the enzyme. This is an example of what kind of inhibition? a. irreversible b. competitive c. non-competitive d. mixed e. pH inhibition

a. irreversible

At pH 7.0, converting an aspartic acid to b-carboxyl aspartate, will have what effect on the overall charge of the protein containing it? a. it will become more negative b. it will become more positive. c. it will stay the same. d. there is not enough information to answer the question. e. the answer depends on the salt concentration.

a. it will become more negative

The double-reciprocal transformation of the Michaelis-Menten equation, also called the Lineweaver-Burk plot, is given by: 1/V0 = Km /(Vmax[S]) + 1/Vmax To determine Km from a double-reciprocal plot, you would: a. multiply the reciprocal of the x-axis intercept by −1 b. multiply the reciprocal of the y-axis intercept by −1 c. take the reciprocal of the x-axis intercept d. take the reciprocal of the y-axis intercept e. take the x-axis intercept where V0 = 1/2 Vmax

a. multiply the reciprocal of the x-axis intercept by −1

Three buffers are made by combining a 1 M solution of acetic acid with a 1 M solution of sodium acetate in the ratios shown below. 1M acetic acid:1M sodium acetate Buffer #1: 90mL:10mL Buffer #2: 50mL:50mL Buffer #3: 10mL:90mL Which of these statements is true of the resulting buffers? a. pH of buffer 1 < pH of buffer 2 < pH of buffer 3 b. pH of buffer 1 = pH of buffer 2 = pH of buffer 3 c. pH of buffer 1 > pH of buffer 2 > pH of buffer 3 d. The problem cannot be solved without knowing the value of pKa e. None of the above

a. pH of buffer 1 < pH of buffer 2 < pH of buffer 3

The first step in two-dimensional gel electrophoresis generates a series of protein bands by isoelectric focusing. In a second step, a strip of this gel is turned 90 degrees, placed on another gel containing SDS, and electric current is again applied. In this second step: a. proteins with similar isoelectric points become further separated according to their molecular weights. b. the individual bands become stained so that the isoelectric focus pattern can be visualized. c. the individual bands become visualized by interacting with protein-specific antibodies in the second gel. d. the individual bands undergo a second, more intense isoelectric focusing. e. the proteins in the bands separate more completely because the second electric current is in the opposite polarity to the first current.

a. proteins with similar isoelectric points become further separated according to their molecular weights.

A buffer system consists of a. weak acid and its conjugate base b. weak acid and a proton donor c. weak acid and a proton d. weak acid and a proton acceptor e. weak acid and a any base

a. weak acid and its conjugate base

In one catalytic cycle, the Na+/K+ATPase transporter transports: a. 2 Na+out, 3 K+in, and converts 1 ATP to ADP + Pi b. 3 Na+out, 2 K+in, and converts 1 ATP to ADP + Pi c. 3 Na+in, 2 K+out, and converts 1 ATP to ADP + Pi d. 1 Na+out, 1 K+in, and converts 1 ATP to ADP + Pi e. 2 Na+out, 3 K+in, and converts 1 ADP + Pito ATP

b. 3 Na+out, 2 K+in, and converts 1 ATP to ADP + Pi

Which of the following is not a fat-soluble vitamin? a. A b. C c. D d. E e. K

b. C

Which of the following is least likely to result in protein denaturation? a. Altering net charge by changing pH b. Changing the salt concentration c. Disruption of weak interactions by boiling d. Exposure to detergents e. Mixing with organic solvents such as acetone

b. Changing the salt concentration

The bacterium E. coli requires simple organic molecules for growth and energy—it is therefore a: a. Chemoautotroph b. Chemoheterotroph c. Lithotroph d. Photoautotroph e. Photoheterotroph

b. Chemoheterotroph

D-Glucose is called a reducing sugar because it undergoes an oxidation-reduction reaction at the anomeric carbon. One of the products of this reaction is: a. D-galactose b. D-gluconate c. D-glucuronate d. D-ribose e. muramic acid

b. D-gluconate

In a highly basic solution, pH = 1.3, the dominant form of glycine is: a. NH₂—CH₂—COOH. b. NH₂—CH₂—COO⁻. c. NH₂—CH₃⁺—COO⁻. d. NH₃⁺—CH₂—COOH. e. NH₃⁺—CH₂—COO⁻.

b. NH₂—CH₂—COO⁻.

In eukaryotes, the nucleus is enclosed by a double membrane called the: a. Cell membrane b. Nuclear envelope c. Nucleolus d. Nucleoplasm e. Nucleosome

b. Nuclear envelope

The four covalent bonds in methane (CH4) are arranged around carbon to give which one of the following geometries? a. Linear b. Tetrahedral c. Trigonal bipyramidal d. Trigonal planar e. Trigonal pyramidal

b. Tetrahedral

Which description is correct? a. All the residues in the peptide with sequence "AKLFPIEARQA" have only one chiral center. b. The pI value of the peptide with sequence "AKQHPMLWND" should be around 11.5. c. When the peptide with sequence "CYTTLNKTG" was completely digested by trypsin, we can get one tripeptide and one hexapeptide. d. The peptide with sequence "AKLFPIEARQA" does not contain any aromatic ring. e. The pI value of the peptide with sequence "ESQWMRLGIV" should be around 8.5.

b. The pI value of the peptide with sequence "AKQHPMLWND" should be around 11.5.

Which of the following statements concerning receptor enzymes is correct? a. They are not usually membrane-associated proteins b. They contain an enzyme activity that acts upon a cytosolic substrate c. They contain an enzyme activity that acts upon the extracellular ligand d. They have a ligand-binding site on the cytosolic side of the membrane e. They have an active site on the extracellular side of the membrane

b. They contain an enzyme activity that acts upon a cytosolic substrate

Which one of the following statements is false of enzyme catalysts? a. Their catalytic activity is dependent on pH b. They increase the rate for a given reaction by a maximum of approximately fifty-fold. c. They do not increase the equilibrium constant for a given reaction d. They are not equally active on D and L isomers of a given substrate e. Their effectiveness can be affected by the presence of an inhibitor

b. They increase the rate for a given reaction by a maximum of approximately fifty-fold.

Enzyme X exhibits maximum activity at pH = 6.9. X shows a fairly sharp decrease in its activity when the pH goes much lower than 6.4. One likely interpretation of this pH activity is that: a. a Glu residue on the enzyme is involved in the reaction b. a His residue on the enzyme is involved in the reaction c. the enzyme has a metallic cofactor d. the enzyme is found in gastric secretions e. the reaction relies on specific acid-base catalysis

b. a His residue on the enzyme is involved in the reaction

For amino acids with neutral R groups, at any pH below the pI of the amino acid, the population of amino acids in solution will have: a. a net negative charge. b. a net positive charge. c. no charged groups. d. no net charge. e. positive and negative charges in equal concentration.

b. a net positive charge.

Consider the transport of glucose into an erythrocyte by facilitated diffusion. When the glucose concentrations are 5 mM on the inside and 0.1 mM on the outside, the free-energy change for glucose uptake into the cell is: (These values may be of use to you: R= 8.315 J/mol·K; T= 298 K; 9 (Faraday constant) = 96,480 J/V; N= 6.022x1023/mol.) a. less than 2 kJ/mol. b. about 10 kJ/mol. c. about 30 kJ/mol. d. about -30 kJoule/mol. e. impossible to calculate without knowledge of the membrane potential.

b. about 10 kJ/mol.

Energy requiring metabolic pathways that yield complex molecules from simpler precursors are: a. amphibolic b. anabolic c. autotrophic d. catabolic e. heterotrophic

b. anabolic

In an a helix, the R groups on the amino acid residues: a. alternate between the outside and the inside of the helix. b. are found on the outside of the helix spiral. c. cause only right-handed helices to form. d. generate the hydrogen bonds that form the helix. e. stack within the interior of the helix.

b. are found on the outside of the helix spiral.

An allosteric interaction between a ligand and a protein is one in which: a. binding of a molecule to a binding site affects binding of additional molecules to the same site b. binding of a molecule to a binding site affects binding properties of another site on the protein c. binding of the ligand to the protein is covalent d. multiple molecules of the same ligand can bind to the same binding site e. two different ligands can bind to the same binding site

b. binding of a molecule to a binding site affects binding properties of another site on the protein

A good transition-state analog: a. binds covalently to the enzyme b. binds to the enzyme more tightly than the substrate c. binds very weakly to the enzyme d. is too unstable to isolate e. must be almost identical to the substrate

b. binds to the enzyme more tightly than the substrate

Fatty acids are a component of: a. carotenes b. cerebrosides c. sterols d. vitamin D e. vitamin K

b. cerebrosides

The benefit of measuring the initial rate of a reaction V0 is that at the beginning of a reaction: a. [ES] can be measured accurately. b. changes in [S] are negligible, so [S] can be treated as a constant. c. changes in Km are negligible, so Km can be treated as a constant. d. V0 = Vmax. e. varying [S] has no effect on V0.

b. changes in [S] are negligible, so [S] can be treated as a constant.

During muscle contraction, hydrolysis of ATP results in a change in the: a. conformation of actin b. conformation of myosin c. structure of the myofibrils d. structure of the sarcoplasmic reticulum e. structure of the Z disk

b. conformation of myosin

Enzymes differ from other catalysts in that only enzymes: a. form an activated complex with the reactants b. display specificity toward a single reactant c. fail to influence the equilibrium point of the reaction d. are not consumed in the reaction e. lower the activation energy of the reaction catalyzed

b. display specificity toward a single reactant

Which of the following monosaccharides is not an aldose? a. erythrose b. fructose c. glucose d. glyceraldehyde e. ribose

b. fructose

In a plot of l/V against 1/[S] for an enzyme-catalyzed reaction, the presence of a competitive inhibitor will alter the: a. curvature of the plot b. intercept on the l/[S] axis c. intercept on the l/V axis d. pK of the plot. e. Vmax

b. intercept on the l/[S] axis

The ion channel that opens in response to acetylcholine is an example of a ____________ signal transduction system. a. G protein b. ligand-gated c. receptor-enzyme d. serpentine receptor e. voltage-gated

b. ligand-gated

Protein S will fold into its native conformation only when protein Q is also present in the solution. However, protein Q can fold into its native conformation without protein S. Protein Q, therefore, may function as a ____________ for protein S. a. ligand b. molecular chaperone c. protein precursor d. structural motif e. super secondary structural unit

b. molecular chaperone

When oxygen binds to a heme-containing protein, the two open coordination bonds of Fe²⁺are occupied by: a. one O atom and one amino acid atom b. one O₂ molecule and one amino acid atom c. one O₂ molecule and one heme atom d. two O atoms e. two O₂ molecules

b. one O₂ molecule and one amino acid atom

Non-steroidal anti-inflammatory drugs (NSAIDS) like aspirin and ibuprofen act by blocking production of: a. biological waxes b. prostaglandins c. sphingolipids d. vitamin D e. none of the above

b. prostaglandins

The force that drives an ion through a membrane channel depends upon: a. the charge on the membrane b. the difference in electrical potential across the membrane c. the size of the channel d. the size of the ion e. the size of the membrane

b. the difference in electrical potential across the membrane

The pH of a solution of 1 M HCl is: a. 0 b. 0.1 c. 1 d. 10 e. -1

c. 1

The inner (plasma) membrane of E. coli is about 75% lipid and 25% protein by weight. How many molecules of membrane lipid are there for each molecule of protein? (Assume that the average protein isMr 50,000 and the average lipid is 750.) a. 1 b. 50 c. 200 d. 10,000 e. 50,000

c. 200

Which of the following statements about starch and glycogen is false? a. Amylose is unbranched; amylopectin and glycogen contain many (α1à6) branches b. Both are homopolymers of glucose c. Both serve primarily as structural elements in cell walls d. Both starch and glycogen are stored intracellularly as insoluble granules e. Glycogen is more extensively branched than starch

c. Both serve primarily as structural elements in cell walls

Which of the following is not involved in signal transduction by the b-adrenergic receptor pathway? a. ATP b. Cyclic AMP c. Cyclic GMP d. GTP e. All of the above are involved

c. Cyclic GMP

A neutral mutation has no effect on the properties of the mutated protein. Indicate which of the following would likely be neutral mutations? a. Glu→Asp b. Leu→Val c. Cys→Ala d. Lys→Arg e. All of the above

c. Cys→Ala

Which vitamin is derived from cholesterol? a. A b. B₁₂ c. D d. E e. K

c. D

Which of the following is not correct concerning 2,3-bisphosphoglycerate (BPG)? a. It binds at a distance from the heme groups of hemoglobin b. It binds with lower affinity to fetal hemoglobin than to adult hemoglobin c. It increases the affinity of hemoglobin for oxygen d. It is an allosteric modulator e. It is normally found associated with the hemoglobin extracted from red blood cells

c. It increases the affinity of hemoglobin for oxygen

Which of the following is not correct concerning cooperative binding of a ligand to a protein? a. It is usually a form of allosteric interaction b. It is usually associated with proteins with multiple subunits c. It rarely occurs in enzymes d. It results in a nonlinear Hill Plot e. It results in a sigmoidal binding curve

c. It rarely occurs in enzymes

Which of the following is not correct concerning 2,3-bisphosphoglycerate (BPG)? a. It binds at a distance from the heme groups of hemoglobin. b. It binds with lower affinity to fetal hemoglobin than to adult hemoglobin. c. It stabilizes the Relaxed (R) state of the hemoglobin d. It is normally found associated with the hemoglobin extracted from red blood cells. e. None of the above

c. It stabilizes the Relaxed (R) state of the hemoglobin

Which of the following statements regarding simple Michaelis - Menten enzyme kinetics is correct? a. Km is expressed in terms of a reaction velocity (moles-1) b. Km is the dissociation constant of the enzyme - substrate complex c. Km is the substrate concentration required to achieve half of Vmax d. Km is 1⁄2 Vmax e. Both A and D are correct

c. Km is the substrate concentration required to achieve half of Vmax

Which of the following is correct with respect to the amino acid composition of proteins? a. Larger proteins have a more uniform distribution of amino acids than smaller proteins. b. Proteins contain at least one each of the 20 different standard amino acids. c. Proteins with different functions usually differ significantly in their amino acid composition. d. Proteins with the same molecular weight have the same amino acid composition. e. The average molecular weight of an amino acid in a protein increases with the size of the protein.

c. Proteins with different functions usually differ significantly in their amino acid composition.

Which of the following does not involve cyclic AMP? a. Regulation of glycogen synthesis and breakdown b. Regulation of glycolysis c. Signaling by acetylcholine d. Signaling by epinephrine e. Signaling by glucagon

c. Signaling by acetylcholine

Which one of the following statements about membranes is true? a. Most plasma membranes contain more than 70% proteins b. Sterol lipids are common in bacterial plasma membranes c. Sterol lipids are common in human cell plasma membranes d. Sterol lipids are common in plant cell plasma membranes e. The plasma membranes of all cell types within a particular organism have basically the same lipid and protein composition

c. Sterol lipids are common in human cell plasma membranes

Which of the following is not an appropriate description for van der Waals interactions? a. They involve dipole-dipole interactions. b. Their strength depends on the distance between the two interacting atoms. c. They are highly specific. d. An individual van der Waals interaction does not contribute significantly to the stability of a protein. e. They can involve hydrophobic amino acids.

c. They are highly specific.

A nonapeptide was determined to have the following amino acid composition: Lys, (Arg) 2, (Leu) 2, Val, Asp, Met, Asn. The native peptide was incubated with 1-fluoro-2,4-dinitrobenzene (FDNB) and then hydrolyzed; 2,4-dinitrophenylvaline was identified by HPLC. When the native peptide was exposed to cyanogen bromide (CNBr), a heptapeptide and a dipeptide were recovered. Incubation of the native peptide with trypsin gave a dipeptide, a pentapeptide and two free amino acids; 2,4-Dinitrophenylvaline was recovered from the pentapeptide, and 2,4- dinitrophenylmethionine was recovered from the dipeptide. Native peptide went through pepsin digestion and produced a free Leu, a dipeptide and a hexapeptide; the hexapeptide was further treated with trypsin digestion and generated a dipeptide, a tripeptide and free Arg. The native sequence was determined to be: a. Val-Asp-Leu-Asn-Met-Arg-Arg-Lys-Leu. b. Val-Asp-Leu-Arg-Arg-Met-Asn-Lys-Leu. c. Val-Asp-Leu-Asn-Arg-Arg-Met-Lys-Leu. d. Val-Asp-Leu-Asn-Arg-Lys-Met-Arg-Leu. e. Val-Asp-Leu-Arg-Arg-Asn-Met-Lys-Leu.

c. Val-Asp-Leu-Asn-Arg-Arg-Met-Lys-Leu.

A ligand-gated ion channel (such as the nicotinic acetylcholine receptor) is: a. a charged lipid in the membrane bilayer that allows ions to pass through b. a membrane protein that permits a ligand to pass through the membrane only when opened by the appropriate ion c. a membrane protein that permits an ion to pass through the membrane only when opened by the appropriate ligand d. a molecule that binds to the membrane thereby allowing ions to pass through e. always requires a second ligand to close the channel once it is opened

c. a membrane protein that permits an ion to pass through the membrane only when opened by the appropriate ligand

An integral membrane protein can be extracted with: a. a buffer of alkaline or acid pH b. a chelating agent that removes divalent cations c. a solution containing detergent d. a solution of high ionic strength e. hot water

c. a solution containing detergent

The major carrier of chemical energy in all cells is: a. acetyl triphosphate b. adenosine monophosphate c. adenosine triphosphate d. cytosine tetraphosphate e. uridine diphosphate

c. adenosine triphosphate

Protein kinase A (PKA) is: a. activated by covalent binding of cyclic AMP. b. affected by cyclic AMP only under unusual circumstances. c. allosterically activated by cyclic AMP. d. competitively inhibited by cyclic AMP. e. noncompetitively inhibited by cyclic AMP.

c. allosterically activated by cyclic AMP.

The fluidity of the lipid side chains in the interior of a bilayer is generally increased by: a. a decrease in temperature b. an increase in fatty acyl chain length c. an increase in the number of double bonds in fatty acids d. an increase in the percentage of phosphatidyl ethanolamine e. the binding of water to the fatty acyl side chains

c. an increase in the number of double bonds in fatty acids

One of the enzymes involved in glycolysis, aldolase, requires Zn2+ for catalysis. Under conditions of zinc deficiency, when the enzyme may lack zinc, it would be referred to as the: a. holoenzyme b. coenzyme c. apoenzyme d. prosthetic group e. substrate

c. apoenzyme

A monoclonal antibody differs from a polyclonal antibody in those monoclonal antibodies: a. are labeled with chemicals that can be visualized. b. are produced by cells from the same organism that produced the antigen. c. are synthesized by a population of identical, or "cloned," cells. d. are synthesized only in living organisms. e. have only a single polypeptide chain that can recognize an antigen.

c. are synthesized by a population of identical, or "cloned," cells.

Guanyl cyclase receptor enzymes: a. are all membrane-spanning proteins b. are examples of ligand-gated ion channels c. catalyze synthesis of a phosphate ester d. catalyze synthesis of a phosphoric acid anhydride e. require hydrolysis of ATP in addition to GTP

c. catalyze synthesis of a phosphate ester

An average protein will not be denatured by: a. a detergent such as sodium dodecyl sulfate b. heating to 90°C c. dihydrogen monoxide d. pH 10 e. urea

c. dihydrogen monoxide

The peptide CMAGT has: a. a disulfide bridge. b. five peptide bonds. c. four peptide bonds. d. no free carboxyl group. e. two free amino groups.

c. four peptide bonds.

The reference compound for naming D and L isomers of sugars is: a. fructose b. glucose c. glyceraldehyde d.ribose e. sucrose

c. glyceraldehyde

When the linear form of glucose cyclizes, the product is a(n): a. anhydride b. glycoside c. hemiacetal d. lactone e. oligosaccharide

c. hemiacetal

The fundamental cause of sickle-cell disease is a change in the structure of: a. blood b. capillaries c. hemoglobin d. red cells e. the heart

c. hemoglobin

A protein is in its native conformation when a. it is thermodynamically least stable b. it has the highest Gibbs free energy c. it is in any of its functional, folded states d. it is unfolded e. none of the above

c. it is in any of its functional, folded states

Integrins are: a. membrane proteins that are involved in ion transport b. membrane proteins that are involved in sugar transport c. membrane proteins that mediate cell adhesion d. proteins of the extracellular matrix that bind to cell surface proteins e. proteins that are found at the membrane-cytoplasm interface

c. membrane proteins that mediate cell adhesion

An octapeptide composed of four repeating Gly-Ala units has: a. one free amino group on an Ala residue. b. one free amino group on an Ala residue and one free carboxyl group on a Gly residue. c. one free amino group on a Gly residue and one free carboxyl group on an Ala residue. d. two free amino and two free carboxyl groups. e. two free carboxyl groups, both on Gly residues.

c. one free amino group on a Gly residue and one free carboxyl group on an Ala residue.

In hemoglobin, the transition from T state to R state (low to high affinity) is triggered by: a. Fe²⁺ binding b. heme binding c. oxygen binding d. subunit association e. subunit dissociation

c. oxygen binding

The effects of acetylcholine on the postsynaptic ion channel are mainly due to: a. cyclic nucleotide synthesis b. protein cleavage (proteolysis) c. protein conformational changes d. protein phosphorylation e. protein synthesis

c. protein conformational changes

Proteins are classified within families or superfamilies based on similarities in: a. evolutionary origin. b. physico-chemical properties. c. structure and/or function. d. subcellular location. e. subunit structure.

c. structure and/or function.

The steady state assumption, as applied to enzyme kinetics, implies: a. Km =Ks b. the enzyme is regulated c. the ES complex is formed and broken down at equivalent rates d. the Km is equivalent to the cellular substrate concentration e. the maximum velocity occurs when the enzyme is saturated

c. the ES complex is formed and broken down at equivalent rates

For enzymes in which the slowest (rate-limiting) step is the reaction k2 k2 ES → P Km becomes equivalent to: a. kcat b. the [S] where V0 = Vmax c. the dissociation constant, Kd, for the ES complex d. the maximal velocity e. the turnover number

c. the dissociation constant, Kd, for the ES complex

At the isoelectric pH of a tetrapeptide: a. only the amino and carboxyl termini contribute charge. b. the amino and carboxyl termini are not charged. c. the total net charge is zero. d. there are four ionic charges. e. two internal amino acids of the tetrapeptide cannot have ionizable R groups.

c. the total net charge is zero.

The aqueous solution with the Lowest pH is: a. 0.01 M HCl b. 0.1 M acetic acid (pKa = 4.86) c. 0.1 M formic acid (pKa = 3.75) d. 0.1 M HCl e. 10⁻¹² M NaOH

d. 0.1 M HCl (double check)

13. Which of the following would have the highest pH? a. 1 M HCl b. 1 M NH₃ (pKa = 9.25) c. 0.5 M NaHCO₃ (pKa = 3.77) d. 0.1 M NaOH e. 0.001 M NaOH

d. 0.1 M NaOH

If the free energy change ΔG for a reaction is -46.11 kJ/mol, the reaction is: a. At equilibrium b. Endergonic c. Endothermic d. Exergonic e. Exothermic

d. Exergonic

Which of the following is a heteropolysaccharide? a. Cellulose b. Chitin c. Glycogen d. Hyaluronate e. Starch

d. Hyaluronate

Which of the following is true about the properties of aqueous solutions? a. A pH change from 5.0 to 6.0 reflects an increase in the hydroxide ion concentration ([OH-])of 20% b. A pH change from 8.0 to 6.0 reflects a decrease in the proton concentration ([H+]) by a factor of 100 c. Charged molecules are generally insoluble in water d. Hydrogen bonds form readily in aqueous solutions e. The pH can be calculated by adding 7 to the value of the pOH

d. Hydrogen bonds form readily in aqueous solutions

Dr. Sinclair is trying to separate a protein mixture containing three proteins A, B, C. Protein A: homotetramer, Mr = 20,000, pI = 6; Protein B: monomer, Mr = 80,000, pI = 7; Protein C: monomer, Mr = 13,000, pI = 9. Please choose the correct one form the following descriptions: a. If Dr. Bingham dissolves the mixture in 0.1 M Tris-HCl (pH 7) and uses SDS-PAGE to separate the mixture, the protein bands in the gel from top to bottom should be B-A-C. b. If Dr. Bingham dissolves the mixture in 20 mM phosphate buffer (pH 8) and loads it to an anion exchange column equilibrated with the same buffer, only protein C can bind to the column. c. If Dr. Bingham dissolves the mixture in 0.1 M Tris-HCl (pH 7) and uses size-exclusion column to separate the mixture, protein C will be first eluted. d. If Dr. Bingham dissolves the mixture in 0.1 M Tris-HCl (pH 7) and uses size-exclusion column to separate the mixture, the elution sequence is B-A-C. e. If Dr. Bingham dissolves the mixture in 0.1 M Tris-HCl (pH 7) and uses SDS-PAGE to separate the mixture, the protein bands in the gel from top to bottom should be B-C-A.

d. If Dr. Bingham dissolves the mixture in 0.1 M Tris-HCl (pH 7) and uses size-exclusion column to separate the mixture, the elution sequence is B-A-C.

The macromolecules that serve in the storage and transmission of genetic information are: a. Carbohydrates. b. Lipids c. Membranes d. Nucleic acids e. Proteins

d. Nucleic acids

Which of the following contains an ether-linked alkyl group? a. Cerebrosides b. Gangliosides c. Phosphatidyl serine d. Platelet-activating factor e. Sphingomyelin

d. Platelet-activating factor

Consider an acetate buffer, initially at the same pH as its pKa (4.76). When a large quantity of sodium hydroxide (NaOH) is mixed with this buffer, the: a. pH remains constant. b. pH rises more than if an equal amount of NaOH is added to an acetate buffer initially at pH 6.76. c. pH rises more than if an equal amount of NaOH is added to unbuffered water at pH 4.76. d. Ratio of acetic acid to sodium acetate in the buffer falls. e. Sodium acetate formed precipitates because it is less soluble than acetic acid.

d. Ratio of acetic acid to sodium acetate in the buffer falls.

The α-keratin chains indicated by the diagram below have undergone one chemical step. To alter the shape of the α-keratin chains—as in hair waving—what subsequent steps are required? a. Chemical oxidation and then shape remodeling b. Chemical reduction and then chemical oxidation c. Chemical reduction and then shape remodeling d. Shape remodeling and then chemical oxidation e. Shape remodeling and then chemical reduction

d. Shape remodeling and then chemical oxidation

Which of the following statements about membrane lipids is true? a. Glycerophospholipids are found only in the membranes of plant cells. b. Glycerophospholipids contain fatty acids linked to glycerol through amide bonds. c. Lecithin (phosphatidylcholine), which is used as an emulsifier in margarine and chocolate, is a sphingolipid. d. Some sphingolipids include oligosaccharides in their structure. e. Triacylglycerols are the principal components of erythrocyte membranes

d. Some sphingolipids include oligosaccharides in their structure.

Which of the following is true about the two molecules shown below? a. They have the same configuration b. They are cis-trans isomers c. They are enantiomers of each other d. They are diastereomers of each other e. None of the above

d. They are diastereomers of each other

Which one of the following statements is true of enzyme catalysts? a. They bind to substrates, but are never covalently attached to substrate or product b. They increase the equilibrium constant for a reaction, thus favoring product formation c. They increase the stability of the product of a desired reaction by allowing ionizations, resonance, and isomerizations not normally available to substrates d. They lower the activation energy for the conversion of substrate to product e. To be effective they must be present at the same concentration as their substrates

d. They lower the activation energy for the conversion of substrate to product

The interactions of ligands with proteins: a. are relatively nonspecific b. are relatively rare in biological systems c. are usually irreversible d. are usually transient e. usually result in the inactivation of the proteins

d. are usually transient

Stereoisomers that are nonsuperimposable mirror images of each other are known as: a. anomers b. cis-trans isomers c. diastereoisomers d. enantiomers e. geometric isomers

d. enantiomers

Glucose transport into erythrocytes is an example of: a. active transport b. antiport c. electrogenic uniport d. facilitated diffusion e. symport

d. facilitated diffusion

The amino acid substitution of Val for Glu in Hemoglobin S results in aggregation of the protein because of ___________ interactions between molecules. a. covalent b. disulfide c. hydrogen bonding d. hydrophobic e. ionic

d. hydrophobic

Vmax for an enzyme-catalyzed reaction: a. generally increases when pH increases. b. increases in the presence of a competitive inhibitor. c. is limited only by the amount of substrate supplied. d. is twice the rate observed when the concentration of substrate is equal to the Km. e. is unchanged in the presence of a uncompetitive inhibitor.

d. is twice the rate observed when the concentration of substrate is equal to the Km.

Carbon monoxide (CO) is toxic to humans because: a. it binds to myoglobin and causes it to denature b. it is rapidly converted to toxic CO₂ c. it binds to the globin portion of hemoglobin and prevents the binding of O₂ d. it binds to the Fe in hemoglobin and prevents the binding of O₂ e. it binds to the heme portion of hemoglobin and causes heme to unbind from hemoglobin

d. it binds to the Fe in hemoglobin and prevents the binding of O₂

The type of membrane transport that uses ion gradients as the energy source is: a. facilitated diffusion b. passive transport c. primary active transport d. secondary active transport e. simple diffusion

d. secondary active transport

The Lineweaver-Burk plot is used to: a. extrapolate for the value of reaction rate at infinite enzyme concentration b. determine the equilibrium constant for an enzymatic reaction c. illustrate the effect of temperature on an enzymatic reaction d. solve, graphically, for the rate of an enzymatic reaction at infinite substrate concentration e. solve, graphically, for the ratio of products to reactants for any starting substrate concentration

d. solve, graphically, for the rate of an enzymatic reaction at infinite substrate concentration

The biochemical property of lectins that is the basis for most of their biological effects is their ability to bind to: a. amphipathic molecules b.hydrophobic molecules c. specific lipids d. specific oligosaccharides e. specific peptides

d. specific oligosaccharides

An enzyme-catalyzed reaction was carried out with the substrate concentration initially a thousand times greater than the Km for that substrate. After 9 minutes, 1% of the substrate had been converted to product, and the amount of product formed in the reaction mixture was 12 μM. If, in a separate experiment, one-third as much enzyme and twice as much substrate had been combined, how long would it take for the same amount (12 μM) of product to be formed? a. 1.5 min b. 3 min c. 6 min d. 13.5 min e. 27 min

e. 27 min

An enzyme has a Km for substrate of 10 mM and Vmax of 5 mol L-1 sec-1 at a total enzyme concentration of 1 nM. At [S] = 10 mM, kcat is: a. 2500 per M per sec. b. 5000 per M per sec. c. 1250 per M per sec. d. 2500 per sec. e. 5000 per sec.

e. 5000 per sec.

Which of the following is notinvolved in signal transduction by the b-adrenergic receptor pathway? a. Cyclic AMP synthesis b. GTP hydrolysis c. GTP-binding protein d. Protein kinase e. All of the above are involved.

e. All of the above are involved.

Hydrophobic interactions make important energetic contributions to: a. Binding of a hormone to its receptor protein. b. Enzyme-substrate interactions. c. Membrane structure. d. Three-dimensional folding of a polypeptide chain. e. All of the above are true.

e. All of the above are true.

Which of the following molecules or substances contain, or are derived from, fatty acids? a. Beeswax b. Prostaglandins c. Sphingolipids d. Triacylglycerols e. All of the above contain or are derived from fatty acids

e. All of the above contain or are derived from fatty acids

Which of the following parts of the IgG molecule is involved in binding to an antigen? a. Fab b. Varible domain c. CH¹ d. CH² e. Both a and b are correct.

e. Both a and b are correct.

What functional groups are present on this molecule? a. Carboxyl and aldehyde b. Hydroxyl and aldehyde c. Hydroxyl and ketone d. Hydroxyl and ester e. Carboxyl and ketone

e. Carboxyl and ketone

Which of the following statements about allosteric control of enzymatic activity is false? a. Allosteric effectors give rise to sigmoidal V0 vs. [S] kinetic plots b. Allosteric proteins are generally composed of several subunits c. An effector may either inhibit or activate an enzyme d. Binding of the effector changes the conformation of the enzyme molecule e. Heterotropic allosteric effectors compete with substrate for binding sites

e. Heterotropic allosteric effectors compete with substrate for binding sites

Which of the following is an epimeric pair? a. D-glucose and D-glucosamine b. D-glucose and D-mannose c. D-glucose and L-glucose d. D-lactose and D-sucrose e. L-mannose and L-fructose

e. L-mannose and L-fructose

The Henderson-Hasselbalch equation: a. Allows the graphic determination of the molecular weight of a weak acid from its pH alone. b. Does not explain the behavior of di- or tri-basic weak acids c. Employs the same value for pKa for all weak acids. d. Is equally useful with solutions of acetic acid and of hydrochloric acid. e. Relates the pH of a solution to the pKa and the concentrations of acid and conjugate base.

e. Relates the pH of a solution to the pKa and the concentrations of acid and conjugate base.

Which of the following is not a reducing sugar? a. Fructose b. Glucose c. Glyceraldehyde d. Ribose e. Sucrose

e. Sucrose

The proteins of the Major Histocompatibility Complex (MHC) bind and display: a. antigen fragments b. B cell fragments c. immunoglobin fragments d. macrophage fragments e. T cell fragments

e. T cell fragments

Which of the following statements about protein-ligand binding is correct? a. The Ka is equal to the concentration of ligand when all of the binding sites are occupied b. The Ka is independent of such conditions as salt concentration and pH c. The larger the Ka (association constant), the weaker the affinity d. The larger the Ka, the faster is the binding e. The larger the Ka, the smaller the Kd (dissociation constant)

e. The larger the Ka, the smaller the Kd (dissociation constant)

Which of the following statements concerning signal transduction by the insulin receptor is not correct? a. Activation of the receptor protein kinase activity results in the activation of additional protein kinases b. Binding of insulin to the receptor activates a protein kinase c. Binding of insulin to the receptor results in a change in its quaternary structure d. The receptor protein kinase activity is specific for tyrosine residues on the substrate proteins e. The substrates of the receptor protein kinase activity are mainly proteins that regulate transcription

e. The substrates of the receptor protein kinase activity are mainly proteins that regulate transcription

Which of the following properties of water does not contribute to the fitness of the aqueous environment for living organisms? a. Cohesion of liquid water due to hydrogen bonding b. High heat of vaporization c. High specific heat d. The density of water is greater than the density of ice e. The very low molecular weight of water

e. The very low molecular weight of water

Which of the following statements concerning protein domains is true? a. They are a form of secondary structure. b. They are examples of structural motifs. c. They consist of separate polypeptide chains (subunits). d. They have been found only in prokaryotic proteins. e. They may retain their correct shape even when separated from the rest of the protein.

e. They may retain their correct shape even when separated from the rest of the protein.

Which of the following is not involved in the specificity of signal transduction? a. Interactions between receptor and signal molecules b. Location of receptor molecules c. Structure of receptor molecules d. Structure of signal molecules e. Transmembrane transport of signal molecules by receptor molecules

e. Transmembrane transport of signal molecules by receptor molecules

Which of the following statements about buffers is true? a. A buffer composed of a weak acid of pKa = 5 is stronger at pH 4 than at pH 6. b. At pH values lower than the pKa, the salt concentration is higher than that of the acid. c. The pH of a buffered solution remains constant no matter how much acid or base is added to the solution. d. The strongest buffers are those composed of strong acids and strong bases. e. When pH = pKa, the weak acid and conjugated base concentrations in a buffer are equal.

e. When pH = pKa, the weak acid and conjugated base concentrations in a buffer are equal.

A hydronium ion: a. has the structure H₃O+ b. is a hydrated hydrogen ion c. is a hydrated proton d. is the usual form of one of the dissociation products of water in solution e. all of the above are true

e. all of the above are true

In competitive inhibition, an inhibitor: a. binds at several different sites on an enzyme b. binds covalently to the enzyme c. binds only to the ES complex d. lowers the characteristic Vmax of the enzyme e. binds reversibly at the active site

e. binds reversibly at the active site

To calculate the turnover number of an enzyme, you need to know: a. the enzyme concentration b. the initial velocity of the catalyzed reaction at [S] >> Km c. the initial velocity of the catalyzed reaction at low [S] d. the Km for the substrate e. both A and B

e. both A and B

Serpentine receptors: a. are examples of G (GTP-binding) regulatory proteins b. are mainly involved in the regulation of ion transport c. are present in prokaryotic cells but not in eukaryotic cells d. are present in the nucleus and affect gene expression e. have multiple membrane-spanning helical domains

e. have multiple membrane-spanning helical domains

Ubiquitin is a: a. component of the electron transport system b. protease c. protein kinase d. protein phosphorylase e. protein that tags another protein for proteolysis

e. protein that tags another protein for proteolysis

Steriod hormone response elements (HREs) are __________ , which, when bound to _____________, alter gene expession at the level of ________________. a. intron sequences; activated hormone receptor; translation b. nuclear proteins; hormone; transcription c. plasma membrane proteins; hormone; transcription d. sequences in DNA; receptor-hormone complex; replication e. sequences in DNA; receptor-hormone complex; transcription

e. sequences in DNA; receptor-hormone complex; transcription

The enzyme fumarase catalyzes the reversible hydration of fumaric acid to L-malate, but it will not catalyze the hydration of maleic acid, the cis-isomer of fumaric acid. This is an example of: a. biological activity b. chiral activity c. racemization d. stereoisomerization e. stereospecificity

e. stereospecificity

An α helix would be destabilized most by: a. an electric dipole spanning several peptide bonds throughout the a helix. b. interactions between neighboring Asp and Arg residues. c. interactions between two adjacent hydrophobic Val residues. d. the presence of an Arg residue near the carboxyl terminus of the a helix. e. the presence of two Lys residues near the amino terminus of the a helix.

e. the presence of two Lys residues near the amino terminus of the a helix.

Experiments on denaturation and renaturation after the reduction and reoxidation of the—S—S— bonds in the enzyme ribonuclease (RNase) have shown that: a. folding of denatured RNase into the native, active conformation, requires the input of energy in the form of heat b. native ribonuclease does not have a unique secondary and tertiary structure. c. the completely unfolded enzyme, with all —S—S— bonds broken, is still enzymatically active d. the enzyme, dissolved in water, is thermodynamically stable relative to the mixture of amino acids whose residues are contained in RNase e. the primary sequence of RNase is sufficient to determine its specific secondary and tertiary structure

e. the primary sequence of RNase is sufficient to determine its specific secondary and tertiary structure

The three-dimensional structure of a protein is determined primarily by: a. electrostatic guidance from nucleic acid structure b. how many amino acids are in the protein c. hydrophobic interaction with lipids that provide a folding framework d. modification during interactions with ribosomes e. the sequence of amino acids in the protein

e. the sequence of amino acids in the protein

The number of substrate molecules converted to product in a given unit of time by a single enzyme molecule at saturation is referred to as the: a. dissociation constant. b. half-saturation constant. c. maximum velocity. d. Michaelis-Menten number. e. turnover number.

e. turnover number.

Myoglobin and the subunits of hemoglobin have: a. no obvious structural relationship b. very different primary and tertiary structures c. very similar primary and tertiary structures d. very similar primary structures, but different tertiary structures e. very similar tertiary structures, but different primary structures

e. very similar tertiary structures, but different primary structures

Osmosis is movement of a: a. charged solute molecule (ion) across a membrane b. gas molecule across a membrane c. nonpolar solute molecule across a membrane d. polar solute molecule across a membrane e. water molecule across a membrane

e. water molecule across a membrane

3. Which of the following pairs is interconverted in the process of mutarotation? a. D-glucose and D-fructose b. D-glucose and D-galactose c. D-glucose and D-glucosamine d. D-glucose and L-glucose e. α-D-glucose and β-D-glucose

e. α-D-glucose and β-D-glucose

A sequence of amino acids in a certain protein is found to be -Ser-Gly-Pro-Gly-. The sequence is most probably part of a(n): a. antiparallel β sheet. b. parallel β sheet. c. α helix. d. α sheet. e. β turn.

e. β turn.