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CHEM 46 > Mixed 2 > Flashcards

Mixed 2 Flashcards

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1
Q

Which amino acid is directly converted to oxaloacetate in the Krebs cycle?
A) Aspartate
B) Alanine
C) Glutamate
D) Serine

A

A) Aspartate

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2
Q

What are the three enzymes involved in the ubiquitination process?

A

E1 (Ubiquitin-activating enzyme), E2 (Ubiquitin-conjugating enzyme), E3 (Ubiquitin-protein ligase)

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3
Q

Which enzyme catalyzes the conversion of argininosuccinate to arginine and fumarate?
A) Argininosuccinate synthase
B) Ornithine transcarbamoylase
C) Argininosuccinate lyase
D) Arginase

A

C) Argininosuccinate lyase

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4
Q

True or False: All proteins are hydrolyzed into free amino acids.

A

False

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5
Q

Which enzyme catalyzes the transfer of the amino group of aspartate to a-ketoglutarate?
A) Alanine aminotransferase
B) Aspartate aminotransferase
C) Glutamate dehydrogenase
D) Serine dehydratase

A

B) Aspartate aminotransferase

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6
Q

True or False: The liver is the major site of amino acid degradation in mammals.

A

True

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7
Q

Which amino acid can be directly converted into NH4+ without first being transferred to a-ketoglutarate?
A) Serine
B) Alanine
C) Aspartate
D) Glutamate

A

A) Serine

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8
Q

What prosthetic group is required for the transamination reaction?

A

Pyridoxal phosphate (PLP)

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9
Q

True or False: Glutamate dehydrogenase catalyzes the oxidative deamination of glutamate.

A

True

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10
Q

What is the product when alanine reacts with a-ketoglutarate?

A

Pyruvate and Glutamate

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11
Q

True or False: Asparagine is directly transaminated into oxaloacetate.

A

False

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12
Q

Which enzyme catalyzes the hydrolysis of asparagine to aspartate?
A) Aspartate aminotransferase
B) Asparaginase
C) Glutaminase
D) Serine dehydratase

A

B) Asparaginase

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13
Q

True or False: Glutamine is converted to glutamate by glutaminase.

A

True

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14
Q

Which amino acid can be converted into acetyl-CoA and glycine?
A) Serine
B) Threonine
C) Alanine
D) Cysteine

A

B) Threonine. Can be converted to Acetyl-CoA or glycine with the enzyme threonine dehydrogenase.

A) Converted to pyruvate, which can then be converted to acetyl-CoA, but it is not directly converted to glycine.
C) Primarily converted to pyruvate.
D) Converted to pyruvate or to other sulfur-containing compounds, but not directly to acetyl-CoA or glycine.

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15
Q

What intermediate is formed when serine is deaminated?

A

Pyruvate and NH4+

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16
Q

True or False: The urea cycle begins with the nucleophilic acyl substitution of ornithine with carbamoyl phosphate.

A

True

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17
Q

Which enzyme catalyzes the formation of citrulline from ornithine and carbamoyl phosphate?
A) Argininosuccinate synthase
B) Ornithine transcarbamoylase
C) Arginase
D) Serine dehydratase

A

B) Ornithine transcarbamoylase

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18
Q

True or False: Fumarate is a product of the urea cycle.

A

True

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19
Q

What is the final product of the urea cycle?

A

Urea

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20
Q

True or False: The conversion of ammonia into urea begins with its reaction with bicarbonate ion and ATP.

A

True

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21
Q

True or False: Branched-chain amino acids are primarily degraded in the liver.

A

False

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22
Q

Which enzyme catalyzes the transamination of alanine to pyruvate?
A) Aspartate aminotransferase
B) Alanine aminotransferase
C) Glutamate dehydrogenase
D) Serine dehydratase

A

B) Alanine aminotransferase

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23
Q

True or False: Threonine dehydratase is involved in the direct deamination of threonine.

A

True

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24
Q

What is the primary site of amino acid degradation in mammals?

A

Liver

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25
Q

True or False: Glutamate dehydrogenase requires NAD+ for the oxidative deamination of glutamate.

A

True

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26
Q

Which amino acid is converted into oxaloacetate via transamination?
A) Alanine
B) Aspartate
C) Glutamate
D) Serine

A

B) Aspartate

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27
Q

True or False: Alanine is directly converted to acetyl-CoA.

A

False

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28
Q

Which amino acid can be converted to pyruvate through transamination?
A) Alanine
B) Glutamate
C) Aspartate
D) Serine

A

A) Alanine

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29
Q

True or False: Leucine is a ketogenic amino acid.

A

True. Leucine is broken down into acetyl-CoA and acetoacetate, both of which are ketone body precursors. It cannot be converted into glucose.

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30
Q

What is the final product of the oxidative deamination of glutamate?

A

NH4+ and α-Ketoglutarate

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31
Q

True or False: All amino acids can be converted to glucose.

A

False

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32
Q

Which cycle converts nitrogen from amino acids into urea?
A) Krebs cycle
B) Calvin cycle
C) Urea cycle
D) Cori cycle

A

C) Urea cycle

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33
Q

True or False: Citrulline is an intermediate in the urea cycle.

A

True

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34
Q

Which enzyme catalyzes the formation of arginine in the urea cycle?
A) Argininosuccinate synthase
B) Ornithine transcarbamoylase
C) Argininosuccinate lyase
D) Arginase

A

C) Argininosuccinate lyase

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35
Q

True or False: The urea cycle is linked to the Krebs cycle through fumarate.

A

True

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36
Q

Which molecule is the carrier of activated carbon dioxide in the urea cycle?
A) Biotin
B) Ubiquitin
C) Carbamoyl phosphate
D) Pyridoxal phosphate

A

C) Carbamoyl phosphate

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37
Q

True or False: Fumarate is produced in the conversion of argininosuccinate to arginine.

A

True

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38
Q

What is the source of the first nitrogen atom in the urea cycle?

A

Ammonia

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39
Q

True or False: The liver is the only organ capable of performing the urea cycle.

A

True

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40
Q

Which molecule serves as the initial acceptor of the nitrogen in the urea cycle?
A) Ornithine
B) Citrulline
C) Arginine
D) Fumarate

A

A) Ornithine

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41
Q

What is the equation used to relate the equilibrium constant Keq to the Gibbs free energy change (ΔG°)?
A) ΔG° = -RTlnKeq
B) ΔG° = RTlnKeq
C) Keq = ΔG°/RT
D) Keq = -ΔG°/RT

A

A) ΔG° = -RTlnKeq

42
Q

True or False: For an exergonic (spontaneous) reaction, the reactants are more stable than the products.

A

False

43
Q

Which of the following factors affect the rate of an enzyme-catalyzed reaction?
A) Concentration of substrate
B) Temperature
C) pH
D) All of the above

A

D) All of the above

44
Q

True or False: Noncompetitive inhibitors bind to the allosteric site of the enzyme-substrate complex.

A

True

45
Q

Which of the following is NOT a type of reversible enzyme inhibition?
A) Competitive
B) Noncompetitive
C) Uncompetitive
D) None of the above

A

D) None of the above

46
Q

In the Michaelis-Menten equation for enzyme kinetics, what does the parameter Vmax represent?
A) The maximum rate of reaction
B) The substrate concentration
C) The enzyme concentration
D) The dissociation constant

A

A) The maximum rate of reaction

47
Q

True or False: In the Lineweaver-Burk plot for enzyme kinetics, the x-intercept gives -1/Km.

A

True

48
Q

Which of the following best describes a ping-pong reaction mechanism for multi-substrate enzymes?
A) All reactants must bind before any product is released.
B) There is a specific order for binding of substrates and release of products.
C) At least one product is formed before all substrates are bound.
D) The substrates bind randomly with no specific order.

A

C) At least one product is formed before all substrates are bound.

49
Q

In the reaction catalyzed by alkaline phosphatase, what is the substrate?
A) p-Nitrophenol
B) 4-Nitrophenyl phosphate
C) Inorganic phosphate
D) Water

A

B) 4-Nitrophenyl phosphate

50
Q

True or False: The average normal range for alkaline phosphatase activity in adult serum is 20-120 U/L.

A

True

51
Q

The rate of enzymatic browning in fruits is catalyzed by which enzyme?
A) Alkaline phosphatase
B) Polyphenol oxidase
C) Catechol oxidase
D) ATPase

A

B) Polyphenol Oxidase (PPO). It is considered the primary enzyme responsible for enzymatic browning of fruits due to melanin.
However, option C) can also be correct in some situations. Catechol oxidase is more specific to catechol and similar compounds

52
Q

Which of the following is a characteristic of enzymes?
A) They are inorganic catalysts.
B) They increase the activation energy of reactions.
C) They are biomolecules that speed up reactions.
D) They are consumed during the reaction.

A

C) They are biomolecules that speed up reactions.

A) Incorrect. They are organic catalysts, being proteins.
B) Incorrect. Enzymes work by lowering the activation energy of a reaction, which is the energy required to start a chemical reaction.
D) They are not used up in the reaction so they can be used again and again.

53
Q

True or False: The first law of thermodynamics states that energy can be created or destroyed.

A

False. The first law of thermodynamics states that energy cannot be created nor destroyed

54
Q

Which of the following statements about the second law of thermodynamics is correct?
A) Entropy can increase in reversible processes.
B) Entropy always increases in all processes.
C) Entropy can remain the same for reversible processes.
D) Entropy always decreases in all processes.

A

C) Entropy can remain the same for reversible processes.

55
Q

What is the sign of ΔG° for an endergonic reaction?
A) Negative
B) Positive
C) Zero
D) Cannot be determined

A

B) Positive

A) Indicate an exergonic reaction
C) Reaction is at equilibrium

56
Q

Which of the following factors does NOT affect the rate of an enzyme-catalyzed reaction?
A) pH
B) Allosteric interactions
C) Inhibitors
D) Concentration of products

A

D) Concentration of products

57
Q

In the analysis of enzyme kinetics using the Lineweaver-Burk plot, an increase in the y-intercept indicates:
A) An increase in Vmax
B) A decrease in Vmax
C) An increase in Km
D) A decrease in Km

A

B) A decrease in Vmax

58
Q

True or False: Catalysis by enzymes involves increasing the stability of the transition state.

A

False

59
Q

Which of the following statements about free energy is correct?
A) Cells can only use heat energy to do work, not free energy.
B) Free energy measures the energy available to perform work at constant pressure and temperature.
C) Systems at equilibrium have maximum free energy.
D) Free energy of products is always less than free energy of reactants.

A

B) Free energy measures the energy available to perform work at constant pressure and temperature.

60
Q

In the reaction catalyzed by catechol oxidase, what is the substrate?
A) Oxygen
B) Catechol
C) Benzoquinone
D) Melanin

A

B) Catechol

61
Q

True or False: The third law of thermodynamics is applicable to biological systems.

A

False

62
Q

Which of the following represents the enthalpy (ΔH) component of the Gibbs free energy equation?
A) ΔG = ΔH - TΔS
B) ΔG = -TΔS
C) ΔG = ΔH + TΔS
D) ΔG = ΔH/TΔS

A

A) ΔG = ΔH - TΔS

63
Q

What happens when the entropy (ΔS) of a reaction is positive?
A) The reaction becomes more favorable.
B) The reaction becomes less favorable.
C) There is no effect on the reaction.
D) The reaction rate decreases.

A

A) The reaction becomes more favorable.

64
Q

True or False: Substrate-level phosphorylation requires coupling with compounds that have a high energy transfer potential.

A

True

65
Q

Which complex in the electron transport chain is bypassed by the mobile shuttle FADH2?
A) Complex I
B) Complex II
C) Complex III
D) Complex IV

A

A) Complex I

66
Q

What is the final electron acceptor in the electron transport chain?
A) NADH
B) FADH2
C) Oxygen
D) Cytochrome c

A

C) Oxygen

67
Q

True or False: The transport of ATP from the mitochondria is coupled with the transport of ADP and Pi.

A

True

68
Q

Which of the following inhibits oxidative phosphorylation by dissipating the electrochemical gradient?
A) ADP
B) Dinitrophenol
C) Oligomycin
D) Pi

A

B) Dinitrophenol. A chemical uncoupler that disrupts oxidative phosphorylation by dissipating the proton gradient across the inner mitochondrial membrane. It allows protons to re-enter the mitochondrial matrix without passing through ATP synthase, effectively uncoupling electron transport from ATP synthesis. This leads to a decrease in ATP production and an increase in heat generation.

A) does not inhibit oxidative phosphorylation
C) inhibits ATP synthase. Does not dissipate EC gradient.
D) does not inhibit oxidative phosphorylation

69
Q

What is the overall equation for the reaction catalyzed by alkaline phosphatase?
A) 4-Nitrophenyl phosphate → p-Nitrophenol + Inorganic phosphate
B) p-Nitrophenol → 4-Nitrophenyl phosphate + Inorganic phosphate
C) 4-Nitrophenyl phosphate + H2O → p-Nitrophenol + Inorganic phosphate
D) p-Nitrophenol + Inorganic phosphate → 4-Nitrophenyl phosphate + H2O

A

C) 4-Nitrophenyl phosphate + H2O → p-Nitrophenol + Inorganic phosphate

70
Q

True or False: p-Nitrophenol is colorless in solution.

A

False

71
Q

What is the function of magnesium chloride in the alkaline phosphatase assay?
A) It acts as a buffer.
B) It is a substrate.
C) It is an inhibitor.
D) It enhances the enzyme activity.

A

D) It enhances the enzyme activity.

72
Q

Which disease may be indicated by low alkaline phosphatase levels?
A) Liver disease
B) Gallbladder disease
C) Wilson’s disease
D) Osteoporosis

A

C) Wilson’s disease

73
Q

True or False: A decrease in both Km and Vmax in enzyme kinetics indicates competitive inhibition.

A

False. Competitive inhibition when Km increases, but Vmax stays the same.

74
Q

In the Lineweaver-Burk plot for enzyme kinetics with an inhibitor, an increase in the slope indicates:
A) Competitive inhibition
B) Noncompetitive inhibition
C) Uncompetitive inhibition
D) Mixed inhibition

A

Depending on specific scenarios, both A or D are applicable

75
Q

What type of inhibition occurs when the inhibitor binds to the enzyme-substrate complex?
A) Competitive
B) Noncompetitive
C) Uncompetitive
D) Mixed

A

C) Uncompetitive

76
Q

True or False: In the sequential ordered mechanism for multi-substrate enzymes, there is a specific order for binding substrates and release of products.

A

True

77
Q

Which of the following inhibition patterns is characteristic of the ping-pong mechanism?
A) Substrate A vs Product Q - Competitive
B) Substrate B vs Product P - Competitive
C) Substrate A vs Product P - Noncompetitive
D) Substrate B vs Product Q - Noncompetitive

A

C) Substrate A vs Product P - Noncompetitive

78
Q

True or False: The maximum velocity (Vmax) for an enzyme will decrease if the enzyme concentration is increased.

A

False

79
Q

What type of chemical reaction is catalyzed by hydrolase enzymes?
A) Oxidation-reduction
B) Group transfer
C) Bond cleavage with water participation
D) Isomerization

A

C) Bond cleavage with water participation

A) Oxidoreductases
B) Transferases
D) Isomerases

80
Q

Which amino acid residue in enzymes is involved in covalent catalysis?
A) Aspartate
B) Glutamate
C) Serine
D) Histidine

A

C) Serine

81
Q

True or False: Oxidative phosphorylation involves the production of ATP by oxidizing NADH and FADH2.

A

True

82
Q

What is the primary role of cytochrome c in the electron transport chain?
A) Transporting electrons from NADH to Complex I
B) Transporting electrons from FADH2 to Complex II
C) Transporting electrons from Complex III to Complex IV
D) Transporting protons across the inner mitochondrial membrane

A

C) Transporting electrons from Complex III to Complex IV

83
Q

This refers to a series of reactions undergone by a precursor molecule to transform it into a final product molecule.
A. Rection Mechanism
B. Metabolism
C. Metabolic Pathway
D. Metabolomics

A

C. Metabolic Pathway

84
Q

These are metabolic pathways that break down a molecule to harness energy.
A. Catabolic Reactions
B. Diverging Pathway
C. Linear Pathway
D. Anabolic Reactions

A

A. Catabolic Reactions

85
Q

What is energy coupling?
A. Energy coupling is the combination of a highly exergonic reaction with an endergonic reaction leading to an overall reaction that is spontaneous.
B. Energy coupling is the use of light energy from sunlight by autotrophs to synthesize complex biomolecules.
C. Energy coupling is the transfer of a phosphate group from one molecule to ADP to synthesize ATP, the energy currency of the cell.
D. Energy coupling is the production of chemical energy from other forms of energy by living organisms

A

A. Energy coupling is the combination of a highly exergonic reaction with an endergonic reaction leading to an overall reaction that is spontaneous.

B. Photosynthesis
C. Substrate-level phosphorylation
D. Too general, not the best choice

86
Q

The synthesis of fatty acids is which type of metabolic pathway?
A. Circular pathway
B. Catabolic pathway
C. Linear pathway
D. Spiral pathway

A

D. Spiral pathway. Same set of enzymes is used repeatedly in a cyclical manner, but each cycle adds two carbons to the growing fatty acid chain. This creates a spiral pattern of elongation.

A. the starting molecule is regenerated at the end e.g. TCA Cycle
B. Catabolic pathways break down complex molecules into simpler ones, releasing energy. Fatty acid synthesis is anabolic
C. A linear pathway proceeds in a straight line, with each step producing a different intermediate. Fatty acid synthesis is repetitive.

87
Q

What is the difference between a converging pathway and a diverging pathway? Check all correct answers.
A. Converging pathways have one precursor molecules and multiple products while diverging pathways have multiple precursor molecules and one product.
B. Converging pathways harness energy while diverging pathways use energy.
C. Diverging pathways have one precursor molecules and multiple products while converging pathways have multiple precursor molecules and one product.
D. Converging pathways are mainly catabolic pathways while diverging pathways are mainly anabolic pathways.

A

B, C, and D

88
Q

What happens to the energy content of a polypeptide strand when it folds to its three dimensional structure?
A. The enthalpy decreases.
B. The enthalpy increases.
C. The entropy increases
D. The free energy remains the same.

A

A. The enthalpy decreases. Protein folding is driven by the decrease in enthalpy, which results from the formation of numerous favorable interactions within the protein structure.

89
Q

A process may lead to a negative ΔSuniverse.
A. True
B. False

A

B. False

90
Q

This thermodynamic parameter of the universe increases in value when energy movement takes place.

A

Entropy

91
Q

This thermodynamic law allows measurement of absolute entropy values of systems and pure substances.

A

Third Law of Thermodynamics

92
Q

This thermodynamics parameter refers to the total energy content of a system.

A

Internal Energy

93
Q

True or False: The ΔGo of a reaction is -5 kJ/mol at 25oC so the reaction is at equilibrium.

A

False

94
Q

True or False: All complexes and other protein electron carriers involved in the electron transport chain are transmembrane proteins.

A

False. CoQ (Ubiquinone) and Cytochrome c are NOT transmembrane proteins.

95
Q

How many moles of electrons are passed on in one complete reaction of the electron transport chain from Complex I to Complex IV to reduce 1 mole of O2?
A. 4
B. 1
C. 2
D. 8

A

A. 4
Oxygen is reduced to water (H2O) at the end of the ETC. The balanced half-reaction for this process is:
O2 + 4H+ + 4e- → 2H2O

96
Q

Which gradients are created across the inner mitochondrial membrane due to an active electron transport chain? Check all that apply.
A. Charge
B. Entropy
C. Energy
D. Concentration

A

All choices.

97
Q

Which gradients created across the inner mitochondrial membrane are responsible for oxidative phosphorylation Check all that apply.
A. Charge
B. Energy
C. Entropy
D. Concentration

A

A and D

98
Q

Which detergent is often used in the extraction of electron transport chain complexes?
A. Digitonin
B. Cholesterol
C. Sodium dodecyl sulfate (SDS)
D. Triton X-100

A

Depending on the situation, option A and D are acceptable. Digitonin is known for isolating complexes with high cholesterol content while Triton X-100 offers a more broad-spectrum approach to solubilizing a wider range of ETC complexes.

99
Q

All complexes in the electron transport chain create a proton gradient across the inner mitochondrial membrane except for _______.
A. Succinate dehydrogenase
B. Cytochrome bc1 complex
C. Cytochrome c oxidase
D. NADH:ubiquinone oxidoreductase

A

A. Succinate dehydrogenase. It is the only complex in the ETC that does not directly contribute to the proton gradient by pumping protons across the inner mitochondrial membrane, since complex II is bypassed.

100
Q

Which complex in the electron transport chain accepts electrons from NADH?
A. Complex II
B. Complex I
C. Complex III
D. Complex IV

A

B. Complex I. It is specifically designed to accept electrons from NADH and initiate their journey through the electron transport chain.

A. Accepts electrons from FADH2, not NADH.
C. Receives electrons from ubiquinone (which received them from Complex I or Complex II).
D. The final electron acceptor in the chain, receiving electrons from cytochrome c and passing them to oxygen to form water.

CHEM 46 (15 decks)

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