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Mixed 4 Flashcards

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1
Q

What is the primary function of antimicrobial resistance (AMR)?
A) To enhance the effectiveness of antibiotics
B) To resist the effects of antibiotics
C) To promote bacterial growth
D) To inhibit bacterial growth

A

B) To resist the effects of antibiotics

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2
Q

True or False: The salvage pathway for thymine is not energetically demanding.

A

True

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3
Q

What enzyme catalyzes the formation of thymidine in the salvage pathway?
A) Thymidine kinase
B) Thymidylate synthase
C) Thymine phosphorylase
D) Thymidine phosphorylase

A

C) Thymine phosphorylase

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4
Q

True or False: The salvage pathway and de novo pathway for nucleotide synthesis compete with each other.

A

False

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5
Q

What is the first step in the degradation of phenylalanine?
A) Hydroxylation to tyrosine
B) Transamination to pyruvate
C) Decarboxylation to phenylethylamine
D) Oxidation to fumarate

A

A) Hydroxylation to tyrosine. The enzyme phenylalanine hydroxylase adds a hydroxyl group (-OH) to phenylalanine, converting it into tyrosine. This is the initial, rate-limiting step in phenylalanine catabolism.

B) Transamination reactions typically involve transferring an amino group, not a primary step in phenylalanine breakdown.
C) While some decarboxylation reactions occur later in phenylalanine metabolism, this is not the first step.
D) Fumarate is involved in the citric acid cycle. Phenylalanine degradation does eventually connect to the citric acid cycle, but not directly through oxidation as the first step.

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6
Q

True or False: Phenylalanine hydroxylase is a monooxygenase enzyme.

A

True

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7
Q

What is the role of aminotransferases in amino acid metabolism?
A) Transfer amino groups between amino acids and keto acids
B) Degrade amino acids
C) Synthesize amino acids
D) Transport amino acids

A

A) Transfer amino groups between amino acids and keto acids

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8
Q

True or False: Aspartate aminotransferase catalyzes the transfer of the amino group of aspartate to α-ketoglutarate.

A

True

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9
Q

What is the product of the reaction catalyzed by alanine aminotransferase?
A) Pyruvate and glutamate
B) Oxaloacetate and glutamate
C) Fumarate and alanine
D) Acetyl CoA and alanine

A

A) Pyruvate and glutamate

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10
Q

True or False: The α-amino groups of serine and threonine can be directly converted into NH4+.

A

True

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11
Q

What is the role of orotidylate decarboxylase in pyrimidine metabolism?
A) Converts orotidylate to uridylate
B) Converts uridylate to cytidylate
C) Converts thymidylate to uridylate
D) Converts cytidylate to orotidylate

A

A) Converts orotidylate to uridylate (UMP). Orotidylate Decarboxylase catalyzes the removal of a carboxyl group (-COOH) from orotidylate, converting it into uridylate (UMP). This is a critical step because UMP is a precursor to all other pyrimidine nucleotides.

B) This conversion is catalyzed by CTP synthetase, a different enzyme in the pathway.
C) This conversion is part of the thymidylate salvage pathway and is catalyzed by thymidine phosphorylase and uridine phosphorylase.
D) This reaction doesn’t occur in the pyrimidine metabolic pathway.

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12
Q

True or False: UMP is a major pyrimidine nucleotide that is a precursor to RNA.

A

True

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13
Q

What enzyme interconverts nucleoside diphosphates and triphosphates?
A) Nucleoside diphosphate kinase
B) Nucleoside monophosphate kinase
C) Nucleoside triphosphate synthase
D) Nucleoside diphosphate synthase

A

A) Nucleoside diphosphate kinase. Its primary function is to transfer a phosphate group from a nucleoside triphosphate (NTP) to a nucleoside diphosphate (NDP). This reaction is reversible, meaning it can also convert NDPs back to NTPs depending on the cell’s energy needs.

B) This enzyme primarily phosphorylates nucleoside monophosphates (NMPs) to nucleoside diphosphates (NDPs).
C) This name is a more general term and doesn’t specifically refer to the interconversion of NDPs and NTPs.
D) This enzyme is involved in the de novo synthesis of NDPs, not their interconversion with NTPs.

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14
Q

True or False: ATP is the universal currency of energy in cells.

A

True

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15
Q

What is the role of GTP in cellular processes?
A) Serves as an energy source for select biological processes
B) Acts as a universal energy currency
C) Inhibits enzyme activity
D) Degrades nucleotides

A

A) Serves as an energy source for select biological processes

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16
Q

True or False: UDP-glucose participates in the biosynthesis of glycogen.

A

True

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17
Q

What is the starting material for de novo purine synthesis?
A) Amino acids and bicarbonate
B) Activated ribose (PRPP) and base
C) Nucleosides and ATP
D) Amino acids and ATP

A

A) Amino acids and bicarbonate

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18
Q

True or False: Inosinate is an intermediate in purine synthesis.

A

True

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19
Q

What is the role of THF in purine synthesis?
A) Donates one-carbon units
B) Acts as a substrate for synthase enzymes
C) Inhibits synthase enzymes
D) Degrades purines

A

A) Donates one-carbon units. THF’s primary role in purine synthesis is to donate the critical one-carbon units needed at specific points during the construction of the purine ring.

B) While THF interacts with enzymes in the pathway, it primarily functions as a coenzyme (a helper molecule) rather than a direct substrate that gets incorporated.
C) THF is essential for purine synthesis; it doesn’t inhibit the enzymes involved.
D) THF is involved in building purines, not breaking them down.

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20
Q

True or False: Purine bases are assembled already attached to the ribose ring.

A

True

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21
Q

What is the role of HMG-CoA synthase in cholesterol synthesis?
A) Catalyzes the formation of 3-hydroxy-3-methylglutaryl CoA
B) Degrades cholesterol
C) Transports cholesterol
D) Activates cholesterol

A

A) Catalyzes the formation of 3-hydroxy-3-methylglutaryl CoA

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22
Q

True or False: HMG-CoA lyase removes acetyl-CoA from HMG-CoA to yield acetoacetate.

A

True

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23
Q

What is the role of ferredoxin in nitrogen fixation?
A) Provides high-potential electrons
B) Acts as a substrate for nitrogenase
C) Inhibits nitrogenase
D) Degrades nitrogen

A

A) Provides high-potential electrons. Ferredoxin plays a critical role in nitrogen fixation by supplying the high-energy electrons that nitrogenase needs to convert nitrogen gas into ammonia.

B) Nitrogen gas (N2) is the substrate for nitrogenase, not ferredoxin.
C) Ferredoxin is essential for nitrogenase activity, not an inhibitor.
D) Ferredoxin is involved in nitrogen fixation (building ammonia), not nitrogen degradation.

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24
Q

True or False: At least 16 ATP molecules are hydrolyzed for each electron transferred in nitrogen fixation.

A

True. The balanced reaction for nitrogen fixation is:
N2 + 8H+ + 8e- + 16 ATP -> 2NH3 + H2 + 16ADP + 16 Pi

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25
Q

What is the role of phenylalanine hydroxylase in amino acid metabolism?
A) Hydroxylates phenylalanine to tyrosine
B) Degrades phenylalanine
C) Synthesizes phenylalanine
D) Transports phenylalanine

A

A) Hydroxylates phenylalanine to tyrosine

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26
Q

True or False: Tyrosine is transaminated to p-hydroxyphenylpyruvate.

A

True

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27
Q

What is the role of adenylosuccinate synthase in purine metabolism?
A) Converts IMP to adenylosuccinate
B) Converts adenylosuccinate to AMP
C) Converts AMP to IMP
D) Converts GMP to IMP

A

A) Converts IMP to adenylosuccinate

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28
Q

True or False: Adenylosuccinate is non-enzymatically converted into adenylate.

A

True

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29
Q

What is the role of aspartate aminotransferase in amino acid metabolism?
A) Transfers the amino group of aspartate to α-ketoglutarate
B) Degrades aspartate
C) Synthesizes aspartate
D) Transports aspartate

A

A) Transfers the amino group of aspartate to α-ketoglutarate

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30
Q

True or False: The carbon backbone donated by aspartate is lost as fumarate.

A

True

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31
Q

What is the role of alanine aminotransferase in amino acid metabolism?
A) Transfers the amino group of alanine to α-ketoglutarate
B) Degrades alanine
C) Synthesizes alanine
D) Transports alanine

A

A) Transfers the amino group of alanine to α-ketoglutarate

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32
Q

True or False: The α-amino groups of serine and threonine can be directly converted into NH4+.

A

True

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33
Q

What is the role of orotidylate decarboxylase in pyrimidine metabolism?
A) Converts orotidylate to uridylate
B) Converts uridylate to cytidylate
C) Converts thymidylate to uridylate
D) Converts cytidylate to orotidylate

A

A) Converts orotidylate to uridylate (UMP)

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34
Q

True or False: UMP is a major pyrimidine nucleotide that is a precursor to RNA.

A

True

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35
Q

What is the role of cytidine triphosphate synthase in nucleotide metabolism?
A) Converts UTP to CTP
B) Converts CTP to UTP
C) Converts ATP to ADP
D) Converts GTP to GDP

A

A) Converts UTP to CTP

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36
Q

True or False: ATP is used to convert the carbonyl group into a good leaving group in the synthesis of CTP.

A

True

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37
Q

What is the first step in the de novo synthesis of purines?
A) Formation of PRPP
B) Formation of IMP
C) Formation of AMP
D) Formation of GMP

A

A) Formation of PRPP

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38
Q

True or False: The de novo synthesis of purines begins with simple sugars.

A

False. Simple sugars like glucose are metabolized through glycolysis and the pentose phosphate pathway. These pathways produce ribose-5-phosphate, a sugar-derived molecule. Ribose-5-phosphate is a precursor to PRPP (phosphoribosyl pyrophosphate). PRPP is the actual molecule that initiates de novo purine synthesis.

39
Q

What enzyme catalyzes the conversion of UMP to UDP?
A) Nucleoside monophosphate kinase
B) Nucleoside diphosphate kinase
C) Nucleoside triphosphate synthase
D) Nucleoside monophosphate synthase

A

A) Nucleoside monophosphate kinase

40
Q

True or False: UTP is more reactive than UMP.

A

True

41
Q

What is the role of pepsin in protein digestion?
A) Hydrolyzes peptide bonds in proteins
B) Synthesizes proteins
C) Transports proteins
D) Inhibits protein digestion

A

A) Hydrolyzes peptide bonds in proteins

42
Q

True or False: Pepsin is maximally active at pH 2.

A

True

43
Q

What is the role of secretin in the digestive system?
A) Regulates gastric juices in the stomach
B) Synthesizes digestive enzymes
C) Inhibits gastric juices
D) Degrades proteins

A

C) Inhibits gastric juices. Secretin acts as a signal to reduce stomach acidity and promote a more alkaline environment in the small intestine as food enters from the stomach.

A) While secretin does influence gastric juice secretion, its primary role is to inhibit it, not regulate it in a general sense.
B) Secretin doesn’t synthesize digestive enzymes; that’s the role of the pancreas and other digestive organs.
D) Secretin doesn’t directly break down proteins. Protein digestion is primarily carried out by enzymes like pepsin in the stomach and other proteases in the small intestine.

44
Q

True or False: Secretin hormone releases bicarbonate to neutralize excess acid.

A

True

45
Q

True or False: Polyphenol oxidase (PPO) is responsible for the browning of fruits such as bananas.

A

True

46
Q

What is the main reaction catalyzed by catechol oxidase in the experiment?
A) Oxidation of catechol to o-quinones
B) Reduction of catechol to o-quinones
C) Oxidation of catechol to water
D) Reduction of catechol to water

A

A) Oxidation of catechol to o-quinones

47
Q

True or False: p-hydroxybenzoic acid acts as an inhibitor of catechol oxidase.

A

True

48
Q

What technique was used to monitor the catechol concentration in the solution?
A) HPLC
B) UV-Vis Spectroscopy
C) Mass Spectrometry
D) NMR Spectroscopy

A

B) UV-Vis Spectroscopy

49
Q

True or False: The slope of absorbance vs. time can be used to calculate the initial velocity of the enzymatic reaction.

A

True

50
Q

What residues are present at the active site of catechol oxidase?
A) Two zinc ions, six histidine residues, one cysteine residue
B) Two copper ions, six histidine residues, one cysteine residue
C) Two iron ions, six histidine residues, one cysteine residue
D) Two magnesium ions, six histidine residues, one cysteine residue

A

B) Two copper ions, six histidine residues, one cysteine residue

51
Q

True or False: The copper ions in catechol oxidase transition among met-, oxy-, and deoxy-forms during catalysis.

A

True

52
Q

What type of inhibition is exhibited by p-hydroxybenzoic acid?
A) Competitive inhibition
B) Non-competitive inhibition
C) Uncompetitive inhibition
D) Mixed inhibition

A

A) Competitive inhibition

53
Q

True or False: PPOs cause more than 50% of losses during pre-harvest and post-harvest processing of fruit and vegetables.

A

True

54
Q

What is the biological importance of PPOs?
A) They catalyze the oxidation of ortho-diphenols to o-quinones
B) They degrade proteins
C) They synthesize carbohydrates
D) They inhibit enzyme activity

A

A) They catalyze the oxidation of ortho-diphenols to o-quinones

55
Q

True or False: The enzyme pepsin is responsible for the digestion of proteins in food.

A

True

56
Q

What is the function of rennin in digestion?
A) Digests proteins in adults
B) Digests milk protein in infants
C) Synthesizes carbohydrates
D) Inhibits enzyme activity

A

B) Digests milk protein in infants

57
Q

True or False: Histamine causes the release of more stomach acid.

A

True

58
Q

How does alcohol affect digestion?
A) Speeds up digestion
B) Irritates the stomach lining and delays digestion
C) Increases enzyme activity
D) Neutralizes stomach acid

A

B) Irritates the stomach lining and delays digestion

59
Q

True or False: The stomach protects itself from its own secretions by forming a thick, bicarbonate-rich mucus layer.

A

True

60
Q

What hormone acts as a brake to ensure a balanced digestive environment?
A) Gastrin
B) Somatostatin
C) Secretin
D) Cholecystokinin

A

B) Somatostatin

61
Q

True or False: The augmented histamine test is an invasive method to measure gastric juice pH.

A

True

62
Q

What condition is characterized by damage to the stomach lining, leaving it exposed to acid?
A) Duodenitis
B) Duodenal ulcer
C) Gastritis
D) GERD

A

B) Duodenal ulcer

63
Q

True or False: Pancreatin contains trypsin, amylase, and lipase.

A

True

64
Q

True or False: The breakdown of vegetable oil by lipase produces fatty acids and glycerols.

A

True

65
Q

What is the principle behind the decolorization of phenolphthalein as an indicator of digestion?
A) It changes color based on pH
B) It reacts with proteins
C) It reacts with carbohydrates
D) It reacts with fats

A

A) It changes color based on pH

66
Q

What is the effect of Orlistat on fat digestion?
A) Inhibits lipase and reduces fat absorption
B) Increases lipase activity
C) Neutralizes stomach acid
D) Increases carbohydrate digestion

A

A) Inhibits lipase and reduces fat absorption

67
Q

True or False: Sodium citrate functions as an activator of glucose metabolism.

A

True

68
Q

What carbohydrate pathway is Pathway A of carbohydrate metabolism by yeast experiment?
A) Anaerobic glycolysis
B) Aerobic glycolysis
C) Fermentation
D) Gluconeogenesis

A

B) Aerobic glycolysis

69
Q

True or False: Methylene blue is colorless under reducing conditions.

A

True

70
Q

True or False: Hexane is a non-polar solvent that readily dissolves non-polar molecules like fats and waxes.

A

True

71
Q

What color is typically associated with the chloroform extract (CE) in plant metabolites?
A) Yellow
B) Green
C) Brown
D) All of the above

A

D) All of the above

72
Q

True or False: Methanol is a highly polar solvent that dissolves polar compounds like phenolics and flavonoids.

A

True

73
Q

What is the rationale for using hexane, chloroform, and methanol in sequence for extraction?
A) To remove non-polar lipids first
B) To extract moderately polar secondary metabolites next
C) To extract polar secondary metabolites last
D) All of the above

A

D) All of the above

74
Q

True or False: The experiment employed a technique called fractionation.

A

True

75
Q

What is the basis of bilirubin quantitation in the experiment?
A) Use of diazonium salts
B) Use of UV-Vis Spectroscopy
C) Formation of a red purple dipyrrole azo derivative
D) All of the above

A

D) All of the above

76
Q

True or False: Alcohol is used to discriminate between conjugated and unconjugated bilirubin.

A

True

77
Q

What does elevated total bilirubin levels indicate?
A) Possible problem with bilirubin metabolism
B) Increased breakdown of red blood cells
C) Problems with bile flow
D) All of the above

A

D) All of the above

78
Q

True or False: High levels of conjugated bilirubin indicate problems with bile flow.

A

True

79
Q

What is the final colored product in the Berthelot reaction for ammonia detection?
A) Indophenol dye
B) Benzoquinone chlorimine
C) Monochloramine
D) Phenol

A

A) Indophenol dye

80
Q

True or False: Urea synthesis is the major pathway for the metabolism of ammonia.

A

True

81
Q

What are the repercussions of abnormal renal pH homeostasis?
A) Acidosis
B) Alkalosis
C) Both A and B
D) None of the above

A

C) Both A and B

82
Q

True or False: Acidosis can lead to bone problems, muscle loss, and irregular heartbeats.

A

True

83
Q

What is the basis of cholesterol quantitation in the experiment?
A) Liebermann-Burchard color reaction
B) Zak color reactions
C) Both A and B
D) None of the above

A

C) Both A and B

84
Q

True or False: Temperature fluctuations can be a potential source of error in cholesterol analysis.

A

True

85
Q

What is the clinical significance of total blood cholesterol level?
A) Indicator of cardiovascular disease risk
B) Essential for various body functions
C) Can lead to atherosclerosis if elevated
D) All of the above

A

D) All of the above

86
Q

True or False: HDL cholesterol is often referred to as “good” cholesterol.

A

True

87
Q

What is the mechanism of action of statin drugs in treating hypercholesterolemia?
A) Inhibit HMG-CoA reductase
B) Increase LDL receptors
C) Lower cholesterol levels
D) All of the above

A

D) All of the above

88
Q

True or False: Statins bind to the allosteric site of HMG-CoA reductase.

A

True

89
Q

What is the primary function of hexane in the extraction protocol?
A) Remove non-polar lipids and pigments
B) Extract moderately polar secondary metabolites
C) Extract polar secondary metabolites
D) None of the above

A

A) Remove non-polar lipids and pigments

90
Q

True or False: Chloroform is a moderately polar solvent.

A

True

91
Q

What compounds are typically dissolved by methanol?
A) Phenolics
B) Flavonoids
C) Tannins
D) All of the above

A

D) All of the above

92
Q

True or False: The presence of pigments can contribute to the color of the chloroform extract.

A

True

93
Q

What is the role of diazonium salts in bilirubin quantitation?
A) Generate colorful reaction products
B) Form a red purple dipyrrole azo derivative
C) Both A and B
D) None of the above

A

C) Both A and B

94
Q

True or False: Elevated unconjugated bilirubin levels indicate increased breakdown of red blood cells.

A

True

CHEM 46 (15 decks)

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