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Biochemistry exam 3 > Board exam questions > Flashcards

Board exam questions Flashcards

1
Q

If the presence of a specific compound, C, increases the Km for an enzyme-substrate reaction, which of the following would be true about that enzyme?

A. C would be a competitive inhibitor of the enzyme.
B. C would be a noncompetitive inhibitor of the enzyme.
C. The velocity vs. [S] plot for the enzyme would be the same with or without C.
D. With C present, the enzyme would convert substrate to product faster.
E. With C present, it would take less substrate to drive the reaction to half-maximum velocity than without C.

A

A

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2
Q

Protein kinase regulate the activities of key enzymes through which of the following?

A.   Oxidation
B.   Hydrolysis
C.   Acetylation
D.   Phosphorylation
E.   Dephosphorylation
A

D

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3
Q

ATP inhibits phosphofructokinase even though ATP also is a substrate for the enzyme. Which of the following types of inhibition BEST explains this phenomenon?

A.   Allosteric
B.   Competitive
C.   Irreversible
D.   Uncompetitive
E.   Noncompetitive
A

A

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4
Q

. Sodium fluoride inhibits glycolysis by affecting

A. amylase
B. enolase
C. phosphatase
D. phosphorylase

A

34 b

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5
Q

. Two enzymes that have been postulated to play very important roles in calcification are

A. enolase and phosphorylase.
B. alkaline phosphatase and catalase.
C. pyrophosphatase and carbonic anhydrase.
D. pyrophosphatase and alkaline phosphatase.
E. carbonic anhydrase and alkaline phosphatase.

A

36D

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6
Q

. Which of the following enzymes is essentially absent from normal mammalian muscle?

A.   Glucokinase
B.   Phosphorylase
C.   Glucose-6-phosphatase
D.   Glucose-6-phosphate isomerase
E.   Glucose-6-phosphate dehydrogenase
A

37 c

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7
Q

Dental plaque arises primarily as a result of enzymatic reactions using which of the following?

A. Sucrose and lipid
B. Sucrose and saliva
C. Glucose and saliva
D. Glucose and protein

A

38 b

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8
Q

Which of the following liver enzymes, absent from other tissues, gives the liver an advantage over other cells in taking up glucose after a meal?

A.   Glucokinase
B.   Aldolase
C.   Hexokinase
D.   Enolase
E.   Glucose-6-phosphatase
A

39 A

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9
Q

. Hydrolysis of sucrose by the enzyme sucrase yields

A.   glucose only.
B.   glucose and maltose.
C.   glucose and fructose.
D.   glucose and galactose.
E.   fructose and maltose.
A

59 C

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10
Q

The arrangement of sugars into D- and L- configurations is based upon their resemblance to D- and L-

A.   glycine.
B.   glucose.
C.   fructose.
D.   glyceraldehyde.
E.   None of the above
A

60 D

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11
Q

. Which of the following is NOT a monosaccharide?

A.   Amylose
B.   Glucose
C.   Fructose
D.   Glyceraldehyde
E.   Glucuronic acid
A

61 A

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12
Q

Some carbohydrates convert Cu2+ ions to Cu+ ions. This property is related to their ability to act as

A. a reducing agent.
B. an oxidizing agent.
C. both a reducing agent and an oxidizing agent.
D. neither a reducing agent nor an oxidizing agent.

A

62 A

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13
Q

What linkages occur in glycogen at branch points between glucose units?

A.   Aplpha-1,4
B.   Alpha-1,6
C.   Beta-1,3
D.   Beta-1,4
E.   Beta-1,6
A

63 B

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14
Q

. How many anomeric carbons are present in a fructose molecule?

A.   0
B.   1
C.   2
D.   5
E.   6
A

64B

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15
Q

Carbohydrate is stored in the body principally as

A.   glucose.
B.   maltose.
C.   sucrose.
D.   glycogen.
E.   glycosaminoglycans.
A

65D

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16
Q

The carbohydrate in highest concentration in resting muscle is

A.   glucose.
B.   lactose.
C.   sucrose.
D.   glycogen.
E.   inositol.
A

70D

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17
Q
  1. Which of the following is LEAST descriptive of lipids?

A. Nonpolar
B. Carbon-containing
C. Amphipathic
D. Hydrophilic

A

D

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18
Q
  1. Carbon dioxide or bicarbonate is required in the biosynthesis of fatty acids because

A. the bicarbonate/carbonic acid buffer system is very efficient at the pH optimum of this sensitive enzyme system.
B. bicarbonate is a positive effector for this system and favorably alters the conformation of its enzymes.
C. carbon dioxide is incorporated into acetyl coenzyme A forming malonyl coenzyme A, an intermediate in the synthetic process.
D. carbon dioxide is incorporated into carbamyl phosphate, a reactive intermediate in the synthetic process.
E. carbon dioxide provides an anaerobic environment that prevents oxidation of the sulfhydryl groups in the reactive sites of the enzyme system.

A

C

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19
Q
  1. The pathway of extramitochondrial synthesis of even-numbered fatty acids differs from that of the catabolism of fatty acids in that

A. malonyl CoA is an intermediate in synthesis.
B. acyl carrier protein is needed in catabolism.
C. no flavoprotein enzymes are required for catabolism.
D. propionyl CoA may serve as an intermediate in synthesis.

A

A

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20
Q
  1. Triglyceride absorbed into the lymphatic system is transported to the liver as which of the following?
A.   Very low density lipoprotein
B.   Low density lipoprotein
C.   Chylomicrons
D.   Liposomes
E.   Micelles
A

C

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21
Q
  1. A common intermediate of metabolism of carbohydrates, fatty acids and amino acids is
A.   glycerol.
B.   acetyl CoA.
C.   acetoacetate.
D.   oxaloacetate.
E.   acetylcholine.
A

B

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22
Q
  1. A number of catabolic pathways are allosterically inhibited by an increase in the concentration of which of the following?
A.   ADP
B.   AMP
C.   ATP
D.   NAD+
E.   Pyruvate
A

C

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23
Q
  1. In the glycolytic sequence, the enzyme that brings about the transition from 6-carbon metabolites to 3-carbon metabolites is
A.   phosphoglucoisomerase.
B.   phosphofructokinase.
C.   phosphorylase.
D.   hexokinase.
E.   aldolase.
A

E

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24
Q
  1. Under strict anaerobic conditions, the catabolism of one glucose molecule would yield a net of

A. 2 ATP and 2 lactic acid molecules.
B. 4 ATP and 2 lactic acid molecules.
C. 2 ATP and 2 pyruvic acid molecules.
D. 4 ATP and 2 pyruvic acid molecules.

A

A

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25
Q
  1. Muscle glycogen does not yield blood glucose directly but liver glycogen does because

A. hexokinase is not present in liver.
B. muscle cells are impermeable to glucose.
C. muscle does not contain phosphoglucomutase.
D. muscle glycogen differs in structure from liver glycogen.
E. glucose-6-phosphatase is not present in muscle.

A

E

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26
Q
  1. Energy for ATP synthesis is derived from the electron transport system by which of the following processes?
A.   Transamination
B.   Aldolization
C.   Reductive synthesis
D.   Oxidative deamination
E.   Oxidative phosphorylation
A

E

27
Q
  1. Functions of the hexose monophosphate shunt include the production of

(1) NADP for lactate oxidation.
(2) NADPH for fatty acid synthesis.
(3) glucuronic acid for heparin synthesis.
(4) D-ribose for nucleic acid synthesis.
(5) ATP for anaerobic muscle contraction.

A.   (1), (3), and (5)
B.   (1) and (4)
C.   (2), (3), and (5)
D.   (2) and (4)
E.   (3) only
A

D

28
Q
  1. Which of the following represents the chemical substance that is the immediate source of energy for muscle contraction?
A.   Glycogen
B.   Acetyl CoA
C.   Lactic acid
D.   Creatine phosphate
E.   Adenosine triphosphate
A

E

29
Q
  1. Enzymes concerned with the citric acid cycle are found in the
A.   nucleus.
B.   ribosomes.
C.   mitochondria.
D.   nonparticulate cytoplasm.
E.   None of the above
A

C

30
Q
  1. The tricarboxylic acid cycle is initiated by the condensation of which of the following two molecules?
A.   Pyruvate and malate
B.   NAD+ and oxaloacetate
C.   NAD+ and oxalosuccinate
D.   Acetyl coenzyme A and oxaloacetate
E.   Acetyl coenzyme A and oxalosuccinate
A

D

31
Q
  1. Enzymes concerned with the citric acid cycle are found in the
A.   nucleus.
B.   ribosomes.
C.   mitochondria.
D.   nonparticulate cytoplasm.
E.   None of the above
A

C

32
Q
  1. Acids found in the citric acid (Krebs) cycle are
A.   glutamic acid and succinic acid.
B.   glucuronic acid and aspartic acid.
C.   oxaloacetic acid and aspartic acid.
D.   oxaloacetic acid and pyruvic acid.
E.   oxaloacetic acid and α-ketoglutaric acid.
A

E

33
Q
  1. If protein is catabolized for energy, then MOST of the energy is derived from which of the following?
A.   Urea production
B.   Oxidative deamination
C.   Transamination reactions
D.   Cleavage of peptide bonds
E.   Oxidation of α-keto acids derived from amino acids.
A

E

34
Q
  1. Which of the following is the FIRST step in the catabolism of many amino acids?

A. Formation of a dipeptide with glutamate
B. Conjugation of the alpha amino to glucuronate
C. Transamination of the alpha amino to a keto acid
D. Conjugation of the alpha carboxyl group to glucuronate
E. Decarboxylation of the alpha carboxyl group to form a primary amine

A

C

35
Q
  1. After prolonged acidosis, which of the following represents the nitrogenous product that is excreted in high amounts in the urine?
A.   Urea
B.   Ammonia
C.   Uric acid
D.   Creatinine
E.   Aspartic acid
A

B

36
Q
  1. Excessive utilization of fats by the body as a source of energy during disturbances in carbohydrate metabolism can lead to all of the following conditions EXCEPT

A. ketosis.
B. acidosis.
C. ketonuria.
D. alkalosis.

A

D

37
Q
  1. In relative insulin insufficiency, acetyl CoA is usually channeled into
A.   ketone-body formation.
B.   cholesterol synthesis.
C.   fatty-acid synthesis.
D.   gluconeogenesis.
E.   the Krebs cycle
A

A

38
Q
  1. The final step in the complete metabolism of fat is carried out by means of
A.   anaerobic glycolysis.
B.   the tricarboxylic acid cycle.
C.   the reductive fixation of CO2.
D.   the hexose monophosphate shunt.
E.   the Krebs-Henseleit (urea) cycle.
A

B

39
Q
  1. Mobilization of fat stored in adipocytes involves

A. activation of fatty acids by synthesis of acyl CoA.
B. rearrangement of fatty acids in triglycerides.
C. phosphorylation of glycerol at the expense of ATP.
D. activation of triglyceride lipase by ADP.
E. activation of triglyceride lipase by a cAMP dependent protein kinase.

A

E

40
Q
  1. How do inadequate insulin levels, such as those which occur in diabetes mellitus, affect fat metabolism?

A. Glucose utilization is increased.
B. Utilization of fat for energy is increased.
C. Storage of cholesterol by the Kupffer cells is increased.
D. Level of beta-hydroxybutyric acid in the urine is depressed.

A

B

41
Q
  1. Which of the following is necessary for de novo synthesis of cholesterol?
A.   NAD+
B.   NADH
C.   NADP+
D.   NADPH
E.   FADH2
A

D

42
Q
  1. Most endogenous cholesterol in the liver is usually converted into which of the following?
A.   Glucose
B.   Steroids
C.   Cholic acid
D.   Oxaloacetate
E.   Ketone bodies
A

C

43
Q
  1. Ribose phosphate needed for nucleic acid synthesis can be derived from

A. gluconeogenesis.
B. the pentose phosphate pathway.
C. the Krebs’ tricarboxylic acid cycle.
D. decarboxylation of aromatic amino acids.
E. one-carbon transfer from tetrahydrofolate derivatives.

A

B

44
Q
  1. Lipid is required in the average diet because it

A. has a high caloric value.
B. provides essential fatty acids.
C. aids in absorption of carbohydrates.
D. is necessary for storage of carbohydrates.

A

B

45
Q
  1. Which of the following must be digested before being in a form that can be absorbed by enterocytes?
A.   Monoglycerides
B.   Fatty acids
C.   Fructose
D.   Glycine
E.   Maltose
A

E

46
Q
  1. A sustained, severe carbohydrate deficiency in the diet will result in which of the following?

A. Ketoacidosis
B. Severe metabolic alkalosis
C. A deficiency in prostaglandin formation
D. An inability to synthesize ascorbic acid

A

A

47
Q
  1. Epinephrine causes an elevation in cAMP levels in muscle cells which in turn activate
A.    ATPase.
B.   adenyl cyclase.
C.   glycogen synthetase.
D.   glycogen phosphorylase.
E.   glycogen phosphorylase phosphatase.
A

D

48
Q
  1. Two hormones which act similarly to increase glycogen and lipid breakdown as well as cyclic AMP synthesis are

A. insulin and calcitonin.
B. glucagon and epinephrine.
C. aldosterone and testosterone.
D. parathyroid hormone and glucagon.

A

B

49
Q
  1. Which of the following is a principal action of insulin?

A. To mobilize lipid deposits
B. To enhance cell permeability to glucose
C. To decrease cell permeability to glucose
D. To conserve glucose by breaking down amino acids

A

B

50
Q
  1. Aldosterone is normally associated with partial regulation of which of the following processes?
A.   Sodium balance
B.   Gluconeogenesis
C.   Lipid digestion
D.   Protein degradation
E.   Carbohydrate metabolism
A

A

51
Q
  1. The mechanism of systemic fluoride action in reducing dental decay is most likely the result of

A. an increase in hardness of the tooth.
B. an inhibition of proteolytic enzymes.
C. deposition of CaF2 in areas of enamel susceptible to bacterial penetration.
D. an increase in carbohydrate metabolism in the oral cavity as a result of enzyme inhibition.
E. a reduction in rate of solubilization of enamel as fluoride content of the tissue increases.

A

E

52
Q
  1. Fluoroapatite can form during hard tissue formation by a (an)

A. substitution of OH ions by F ions.
B. reaction between CaF2 and CaHPO4.
C. reaction of F ions with hydroxylysine residues.
D. absorption of F ions onto hydroxyapatite crystal surfaces.

A

A

53
Q
  1. Which of the following statements is NOT true concerning fluoride?

A. It is expected rapidly by the kidney.
B. It is deposited in calcified tissues.
C. It occurs only in the ionic form in plasma.
D. It passes the placental barrier relatively slowly.
E. At 1 ppm. In water, it is tasteless, odorless and colorless.

A

C

54
Q
  1. The anticaries effect of fluoride is LEAST related to which of the following?

A. Ion exchange
B. Decreased solubility
C. Facilitation of remineralization
D. Its presence during enamel formation
E. Activation of plaque polysaccharide hydrolysis

A

E

55
Q
  1. The rate of fluoride incorporation into bone depends upon the

A. water-mineral ratio.
B. age of the individual.
C. rate of bone remodeling or turnover.
D. amount of ionizable fluoride in the diet.
E. All of the above

A

E

56
Q
  1. Sodium fluoride inhibits glycolysis by affecting which of the following?

A. Amylase
B. Enolase
C. Phosphatase
D. Phosphorylase

A

B

57
Q
  1. Which of the following sweeteners is non-nutritive as well as non-cariogenic?
A.   D-fructose
B.   Saccharin
C.   Galactose
D.   Sorbitol
E.   Maltose
A

B

58
Q

A10. What are predominant linkages in glycogen between glucose units?

A.	Alpha-1,4
B.	Alpha-1,6
C.	Beta-1,3
D.	Beta-1,4
E.	Beta-1,6
A

A

59
Q

A11. Glucose can be made from each of the following substances EXCEPT one. Which one is this EXCEPTION?

A.	Lactate
B.	Acetyl CoA
C.	Glycerol
D.	Pyruvate
E.	Fructose
A

B

60
Q

A14. Glucose-6-phosphatase is found associated with which of the following?

A. Kidneys and liver
B. Liver and muscles
C. Kidneys and brain
D. Kidneys and muscles

A

A

61
Q

A26. Each of the following is expected to be active during fatty acid biosynthesis EXCEPT one. Which one is this EXCEPTION?

A.	Tricarboxylic acid cycle
B.	Pyruvate dehydrogenase
C.	Amino acid catabolism 
D.	Beta oxidation
E.	Glycolysis
A

D

62
Q

A27. Which of the following is a ketone body?

A.	Glycerol
B.	Glucagon
C.	Acetyl CoA
D.	Acetoacetate
E.	Phosphatidycholine
A

D

63
Q

A32. Which of the following provides the immediate energy source for the transport of glucose into intestinal epithelial cells?

A. NADH
B. NADPH
C. Na+ gradient across the luminal membrane
D. H+ gradient across the luminal membrane

A

C

64
Q

A34. The catabolism of which of the following results in no energy production in the form of ATP?

A. Lipid
B. Protein
C. Nucleotide
D. Carbohydrate

A

C

Biochemistry exam 3 (15 decks)

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