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Biochemistry > Final Practice Exam > Flashcards

Final Practice Exam Flashcards

1
Q

For a reaction with delta H = 34 kj/mol and delta S = 22 J/K mol, at 2 degrees celsius, the reaction is ______.

-nonspontaneous
-spontaneous
-at equilibrium
-impossible to determine reactivity
-none of the above

A

Nonspontaneous

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2
Q

The pH of coffee is 5.6. The pH of grapefruit juice is 2.6. This means that the proton concentration in coffee is _____.

-3,000 times higher than in grapefruit juice
-1,000 times higher than in grapefruit juice
-3,000 times lower than in grapefruit juice
-3 times the proton concentration of grapefruit juice
-1,000 times lower than in grapefruit juice

A

1,000 times lower than in grapefruit juice

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3
Q

An A-T base pair consists of ______ H-bonds; a C-G base pair consists of _______ H-bonds.

A

2; 3

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4
Q

How does a catalyst increase the rate of a reaction?

-It increases the temperature of the reaction
-It allows reacting molecules to more easily form the transition state
-It causes a localized increase in the concentration of reactants
-It makes the reaction more exergonic
-None of the above

A

It allows reacting molecules to more easily form the transition state

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5
Q

Which of the following statements regarding allosteric enzymes is TRUE?

-A plot of velocity versus [substrate] often yields a sigmoidal curve
-They are always oligomeric
-They are generally found at regulatory sites in metabolic pathways
-They are subject to regulation by both positive and negative effectors
-All of the above

A

All of the above

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6
Q

Which of the following best describes a new strand of DNA relative to the template strand used to synthesize it?

-An exact copy of the template but with the 3’ and 5’ ends reversed
-A palindromic copy of the template
-A negative copy of the template
-An exact duplicate of the template
-None of the above

A

A negative copy of the template

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7
Q

Lysine can form a salt bridge by interacting with the side chain of ______.

-Pro
-Ser
-Glu
-Gly
-Asn

A

Glu

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8
Q

If the Asp in the chymotrypsin active site was mutated to another amino acid, which of the following would be considered an invisible mutation in that it is least likely to affect the function of the enzyme?

-Asp –> Glu
-Asp –> His
-Asp –> Ser
-Asp –> Lys
-Asp –> Asn

A

Asp –> Glu

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9
Q

Which of the following statements describes integral membrane proteins? (Select all that apply.)

-They protect the contents of the cell from chaotropic agents such as urea
-They are easily dissociated from the membrane by changes in pH or high salt concentration
-They are held in place by hydrophobic effects between the membrane and hydrophobic amino acids.

A

They are held in place by hydrophobic effects between the membrane and hydrophobic amino acids.

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10
Q

Activation of a G protein in response to hormone binding requires binding of the _____ to the ____ subunit.

-GTP; alpha
-GDP; beta
-GTP; beta
-GDP; gamma
-GDP; alpha

A

GTP; alpha

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11
Q

Amylopectin contains primarily ______ glycosidic bonds with ______ glycosidic bonds as branch points.

A

Alpha(1–>4); Alpha (1–>6)

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12
Q

Triose phosphate isomerase catalyzes a reaction that is most like that of _______.

-phosphoglucose isomerase
-aldolase
-hexokinase
-enolase
-phosphoglycerate mutase

A

phosphoglucose isomerase

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13
Q

The reaction catalyzed by the enzyme aldolase has a Delta G degree prime ~ + 23 kj/mol. In muscle cells, the reaction proceeds in this same, forward direction. How can this occur?

-The concentration of reactant(s) must be significantly greater than product(s) in cells.
-This Delta G degree prime means it is thermodynamically favored.
-The concentration of product(s) must be significantly greater than reactant(s) in cells.
-The enzyme changes the Delta G of the reaction in cells to something favorable
-None of the above

A

The concentration of reactant(s) must be significantly greater than product(s) in cells.

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14
Q

Which reaction below produces GTP in the citric acid cycle?

-fumarate –> malate
-malate –> oxaloacetate
-Isocitrate –> alpha-ketoglutarate
-Alpha-ketoglutarate –> succinyl-CoA
-succinyl-CoA –> succinate

A

succinyl-CoA –> succinate

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15
Q

Which of the following statements is(are) TRUE about oxidative phosphorylation? (Select all that apply)

-Electron transport provides energy to pump protons into the intermembrane space
-An electrochemical gradient is formed across the inner mitochondrial membrane
-Potassium and sodium ions form an ionic gradient across the inner mitochondrial membrane
-Complexes I, III, and IV actively transport protons into the intermembrane space during electron transport.

A

-Electron transport provides energy to pump protons into the intermembrane space
-An electrochemical gradient is formed across the inner mitochondrial membrane
-Complexes I, III, and IV actively transport protons into the intermembrane space during electron transport.

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16
Q

The imbalance of protons across the inner mitochondrial membrane is referred to as _______.

-the protonmotive force
-the chemiosmotic force
-the electron transport force
-the proton gradient force
-the ATP synthase force

A

the protonmotive force

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17
Q

What is the correct order of intermediates during the synthesis of glycogen?

A

Glucose –> glucose-6-phosphate –> glucose-1-phosphate –> UDP-glucose –> glycogen

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18
Q

Bacterial cell walls are made of ______.

-keratin sulfate
-heparin
-chondroitin sulfate
-pectin
-peptidoglycans

A

peptidoglycans

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19
Q

In the conversion of ribulose-5-phosphate to glycolytic intermediates, which of the following enzymes is used?

-phosphoglucomutase
-phosphofructoisomerase
-phosphoglycerate mutase
-transketolase
-none of the above

A

transketolase

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20
Q

Which of the following is an inhibitor of pyruvate dehydrogenase?

-NADH
-FADH2
-Pyruvate
-CO2
-CoA

A

NADH

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21
Q

What coenzyme is required for the complete beta-oxidation of a polyunsaturated fatty acid?

-FADH2
-NADP+
-NADH
-NADPH

A

NADPH

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22
Q

In which location listed below does the following reaction take place:

HMG-CoA –> acetoacetate + Acetyl-CoA

-cytosol of liver cells
-mitochondria of liver cells
-cytosol of cardiomyocytes
-mitochondria of cardiomyocytes

A

mitochondria of liver cells

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23
Q

Which o f the following is FALSE regarding HMG-CoA reductase?

-HMG-CoA reductase levels are increased because of high cholesterol concentrations in the ER
-HMG-CoA reductase levels are decreased because of high cholesterol concentrations in the ER
-HMG-CoA reductase levels are decreased through sterol response element binding protein (SREBP) transcription factor
-HMG-CoA reductase is highly regulated
-It is often a target of inhibition by cholesterol lowering drugs

A

HMG-CoA reductase levels are increased because of high cholesterol concentrations in the ER

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24
Q

Which of the following is TRUE regarding pancreatic beta cells?

-Insulin is secreted by the beta cells in response to low glucose levels
-Insulin is secreted by the beta cells in response to high glucose levels
-Insulin is secreted by the beta cells in response to the increase in beta cell glucose receptor binding
-Glucagon is secreted by the beta cells in response to high glucose levels
-Glucagon is secreted by the beta cells in response to the increase in beta cell glucose receptor binding

A

Insulin is secreted by the beta cells in response to high glucose levels

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25
Q

Which of the following best describes arachidonic acid?

-a 20-carbon fatty acid essential for cholesterol synthesis
-a 2-carbon compound that functions in conjunction with a fatty acid carrier protein for transport of primed fatty acids
-a 20-carbon fatty acid used for synthesis of prostaglandins
-a 20-carbon isoprene-based intermediate of cholesterol synthesis
-a 20-carbon isoprene-based compound used for synthesis of prostaglandins

A

a 20-carbon fatty acid used for synthesis of prostaglandins

26
Q

Which of the following alcohols is esterified to the phosphate group of glycerophospholipids?

-serine
-glycerol
-ethanolamine
-choline
-all of the above

A

all of the above

27
Q

The amino acids Ala, Cys, Gly, and Ser are all degraded to the metabolic intermediate ______ and are considered ______.

-Acetyl-CoA; glucogenic
-Pyruvate; glucogenic
-Acetoacetate; ketogenic
-Pyruvate; ketogenic
-Acetyl-CoA; ketogenic

A

Pyruvate; glucogenic

28
Q

Oxidative deamination of glutamate… (Select all that apply)

-Generates alpha-ketoglutarate
-is inhibited by glutamate
-is activated by GTP
-eliminates the keto group from alpha-keto acids

A

Generates alpha-ketoglutarate

29
Q

Which of the lipoproteins is responsible for removing cholesterol from cells?

-HDL
-VHDL
-Chylomicron
-LDL
-VLDL

A

HDL

30
Q

Which of the following commonly occurs before cholesterol is packaged into a VLDL?

-phosphorylation by ATP
-hydration of the alkene
-oxidation to increase water solubility
-esterification with a fatty acid
-all of the above may occur

A

esterification with a fatty acid

31
Q

The common products of fuel metabolism in mammals are _______.

-pyruvate and acetyl-CoA
-oxaloacetate and acetyl-CoA
-ATP and acetyl-CoA
-pyruvate and glucose
-none of the above

A

pyruvate and acetyl-CoA

32
Q

Insulin-dependent (type I) diabetes ________.

-is associated with a deficiency of insulin receptors
-can be treated with injections of ghrelin
-is associated with a deficiency of pancreatic beta cells
-can be treated with injections of leptin
-is associated with a deficiency of signal transduction

A

is associated with a deficiency of pancreatic beta cells

33
Q

What species are combined to produce carbamoyl phosphate?

-glycine and inorganic phosphate, releasing CO2
-NH3, PO4 -3, HCO3 -
-acetate and NH4+, releasing CO2
-alanine and inorganic phosphate, releasing acetate

A

NH3, PO4 -3, HCO3 -

34
Q

Enzymes accelerate biochemical reactions by _____.

-providing a more favorable pathway for the reactions
-establishing a “closed system” for each reaction
-promoting reaction pathways associated with a positive delta G
-decreasing the delta G for the reactions
-increasing the delta G for the reactions

A

providing a more favorable pathway for the reactions

35
Q

Which of the following correctly describes the B-DNA double helix?

-one helical rotation has a rise of 3.4 nm
-base pairs are located in the center of the helix
-right-handed helix
-antiparallel strands
-all of the above

A

all of the above

36
Q

The kidney has a small amount of gluconeogenic activity. Which of the following explains the source of carbon for gluconeogenesis?

-conversion of glutamine into glutamic acid, then to alpha-ketoglutarate
-conversion of alanine into pyruvate
-conversion of aspartate into oxaloacetate
-conversion of citrate into acetyl-CoA and oxaloacetate
-conversion of odd-chain fatty acids into succinyl-CoA

A

conversion of glutamine into glutamic acid, then to alpha-ketoglutarate

37
Q

Which of the following functional groups has two hydrogen bond donors and one hydrogen bond acceptor?

-thiol
-amine
-alcohol
-amide
-ester

A

Amine

38
Q

RNA occurs primarily as single-stranded molecules that can give rise to _______ structures.

-stem-loop
-diploid
-haploid
-parallel
-tautomeric

A

stem-loop

39
Q

At a pH above its pKa, the phenolic group of tyrosine is _______.

-deprotonated and negatively charged
-protonated and positively charged
-deprotonated and neutral
-protonated and neutral
-none of the above

A

deprotonated and negatively charged

40
Q

A new drug has been discovered that inhibits the reaction catalyzed by enzyme A. Based on this information, what is the drug?

-uncompetitive inhibitor
-mixed inhibitor
-allosteric activator
-competitive inhibitor
-More information is required to answer this question

A

competitive inhibitor

41
Q

Which of the following is most critical for maintaining the tertiary structure of a protein?

-hydrogen bonds
-hydrophobic interactions
-salt bridges
-disulfide bonds
-none of the above

A

hydrophobic interactions

42
Q

Cells control or regulate the flux through metabolic pathways by means of… (Select all that apply)

-allosteric control of enzymes
-covalent modification of enzymes
-genetic control of the concentration of enzymes
-altering the delta G value of reactions

A

-allosteric control of enzymes
-covalent modification of enzymes
-genetic control of the concentration of enzymes

43
Q

How does the reaction catalyzed by malate dehydrogenase proceed despite a sGs’ of 29.7 kJ/mol?

-Concentrations of oxaloacetate are kept very low by rapid use in the subsequent step
-High levels of NAD+ allow the reaction to proceed
-The enzyme is unique in its ability to catalyze the reaction in only one direction
-An elevated [H+] allows the reaction to proceed
-The enzyme-catalyzed reaction under cellular conditions has a much smaller energy of activation.

A

Concentrations of oxaloacetate are kept very low by rapid use in the subsequent step

44
Q

The formation of a dipeptide from two amino acids requires _______.

-loss of water
-interaction of the two side chains
-reduction of the alpha-carboxyl group
-protonation of the alpha-amine group
-none of the above

A

loss of water

45
Q

A Lineweaver-Burk plot is also referred to as _______. (Select all that apply)

-a sigmoidal plot
-a linear plot
-a Michaelis-Menten plot
-a double reciprocal plot

A

-a linear plot
-a double reciprocal plot

46
Q

What three amino acids are found in the catalytic triad of chymotrypsin, a protease which acts in the small intestine?

A

Asp, His, Ser

47
Q

A pore that simultaneously transports two different molecules in different directions is called ______.

-a gap junction
-an antiport
-a uniport
-an equilibrium channel
-a symport

A

an antiport

48
Q

Which of the following represents the net products of glycolysis from one molecule of glucose?

-6 CO2, 30 ATP
-2 pyruvate, 2 NADH, 2 ATP
-2 pyruvate, 2 NADH, 4 ATP
-3 pyruvate, 2 NADH, 4 ATP
-6 CO2, 32 ATP

A

2 pyruvate, 2 NADH, 2 ATP

49
Q

Why is phosphoglycerate kinase still considered a kinase even though ADP is converted to ATP?

-ATP is the ultimate source of the phosphate that is transferred to ADP
-The phosphate is transferred in conjunction with an oxidative reaction
-The enzyme is freely reversible
-The reaction is metabolically irreversible
-None of the above

A

The enzyme is freely reversible

50
Q

A common type of covalent modification of regulatory enzymes involves ______ of serine residues.

A

phosphorylation

51
Q

Leucine has a _______ side chain; glutamate has a ______ side chain

A

nonpolar; charged

52
Q

________ are amphipathic molecules that constitute the major lipid components.

A

Phospholipids

53
Q

The products of glycolysis include ATP, NADH, and ______

A

pyruvate

54
Q

Glucose can be synthesized from noncarbohydrate precursors by _______.

A

gluconeogenesis

55
Q

________ and pyruvate can be combined in an ATP-dependent reaction that regenerates one of the key intermediates in the citric acid cycle

A

CO2

56
Q

NADPH used in lipid biosynthesis is produced by the _______ pathway.

A

Pentose phosphate

57
Q

The beta-oxidation of odd-numbered fatty acids results in ________ as a final product.

A

Propionyl-CoA

58
Q

The molecules acetoacetate, acetone, and D-beta-hydroxybutyrate are metabolic fuels termed ________.

A

ketone bodies

59
Q

The amino acid ______ has been thought to act as a transfer system for NH3, safely allowing the toxic molecule to be transported from the liver to kidneys.

A

Glutamate

60
Q

________ is the degradation product of glucose, fatty acids, and ketogenic amino acids.

A

Acetyl-CoA

61
Q

During starvation the ______ generates as much as 50% of the body’s glucose supply.

A

kidneys

Biochemistry (5 decks)

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