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MCAT > Biochemistry Ch. 2 > Flashcards

Biochemistry Ch. 2 Flashcards

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MCAT flashcards
1
Q

Catalysts do no impact delta ____ or ____

A

Delta H, delta G, or the equilibrium position

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2
Q

Enzymes (raise/lower) activation energy

A

lower

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3
Q

Enzymes (increase/decrease) the rate of reaction

A

Increase

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4
Q

Enzymes (do/don’t) alter equilibrium constant

A

Don’t

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5
Q

List the six categories of enzymes

A

LIL HOT:

1) Ligase
2) Isomerase
3) Lyase
4) Hydrolase
5) Oxidoreductase
6) Transferase

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6
Q

Define oxidoreductases

A

Category of enzyme that catalyzes oxidation-reduction reactions

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7
Q

What category of enzymes often has a cofactor that acts as an electron carrier

A

Oxidoreductases

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8
Q

Define reductant

A

Electron donor

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9
Q

Define oxidator

A

Electron acceptor

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10
Q

Enzymes with dehydrogenase or reductase in their names are usually what category of enzymes?

A

Oxidoreductases

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11
Q

Oxidases have ___ as the final electron receptor

A

Oxygen

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12
Q

Define transferase

A

Category of enzymes that catalyze the movement of a functional group from one molecule to another

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13
Q

How does aminotransferase work?

A

Can convert aspartate and alpha-ketoglutarate to glutamate and oxaloacetate by moving the amino group from aspartate to alpha-ketoglutarate.

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14
Q

Kinases are an example of what category of enzyme?

A

Kinases

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15
Q

Aminotransferase is any example of what category of enzyme?

A

Transferase

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16
Q

Define kinase

A

Catalyze the transfer of a phosphate group (usually from ATP) to another molecule

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17
Q

Define Hydrolase

A

A category of enzyme that catalyzes the breaking of a compound into 2 molecules using the addition of water

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18
Q

What category of enzyme is phosphatase?

A

Transferase

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19
Q

Describe the mechanism of phosphatase

A

Cleaves a phosphate group from another molecule

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20
Q

Peptidase is an example of what category of enzyme?

A

Hydrolase

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21
Q

Nuclease is an example of what category of enzyme?

A

Hydrolase

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22
Q

Lipase is an example of what category of enzyme?

A

Hydrolase

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23
Q

Define peptidase

A

A hydrolase that breaks down proteins

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24
Q

Define nuclease

A

A hydrolase that breaks down nucleic acids

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25
Q

Define lipase

A

A hydrolase that breaks down lipids

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26
Q

Define lyase

A

A category of enzyme that catalyzes the cleavage of a single molecule into 2 products or can synthesize 3 products into 1 molecule

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27
Q

Lyases do not require ____ as a substrate

A

water

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28
Q

Define synthase

A

A lyase that catalyzes the synthesis of 2 products into 1 molecule

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29
Q

List examples of oxidoreductases

A

Most enzymes with dehydrogenase or reductase in their names

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30
Q

List 2 examples of a transferase

A

aminotransferase and kinases

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31
Q

List 4 examples of hydrolases

A

phosphatases, peptidases, nucleases, lipases

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32
Q

Define isomerase

A

A category of enzyme that catalyzes the rearrangement of bonds within a molecule

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33
Q

Depending on the mechanism of the enzyme, isomerases can also be classified as ________

A

Oxidoreductases, transferases, lyases

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34
Q

Define ligase

A

A category of enzyme that catalyzes addition or synthesis reactions. typically between larger molecules

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35
Q

Ligases often require _____

A

ATP

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36
Q

Synthesis reactions with small molecules are usually catalyzed by ____ while synthesis reactions with large molecules are usually catalyzed by ____

A

Lyases; ligase

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37
Q

Enzymes can affect the ____ but not the ___ of a reaction

A

Kinetics; thermodynamics

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38
Q

If a reaction is endergonic, energy is ___ and delta G is ___

A

required; G>0

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39
Q

If a reaction is exergonic, energy is ___ and delta G is ___

A

released; G<0

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40
Q

The active site is stabilized by _______

A

H bonding, ionic interactions, and transient covalent bonds

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41
Q

The ___ part of the induced fit model is endergonic

A

The substrate changing shape to respond to the enzyme

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42
Q

The ___ part of the induced fit model is exergonic

A

Release of the enzyme from susbtrate, causing both enzyme and substrate to resume relaxed, non-induced forms

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43
Q

Define cofactor

A

small inorganic molecules or metal ions that bind to the active site of an enzyme and participate in the catalysis of a reaction

44
Q

Define co-enzyme

A

small organic groups that bind to the active site of an enzyme and participate in the catalysis of a reaction

45
Q

Cofactors are often ingested as ______

A

dietary minerals

46
Q

Define apoenzyme

A

Enzymes without cofactors

47
Q

Define holoenzyme

A

Enzymes with cofactors

48
Q

Define prosthetic groups

A

Tightly bound cofactors or coenzymes that are necessary for enzyme function

49
Q

Coenzymes are usually ___ or ___ derivatives

A

Vitamin

50
Q

NAD+. FAD, and coenzyme A are examples of ___

A

coenzymes

51
Q

List 3 examples of a coenzyme

A

NAD+. FAD, and coenzyme A

52
Q

List the water-soluble vitamins that also act as coenzymes

A

B and ascorbic acid (C) vitamins

53
Q

List the fat-soluble vitamins that also act as coenzymes

A

A, D, E, K

54
Q

Fat soluble vitamins are regulated by _____

A

Partition coefficients

55
Q

Define partitions coefficient

A

Quantify ability of molecule to dissolve in a polar vs non polar environment

56
Q

Increasing ___ will increase the rate of the reaction (reaction velocity = v) until reaching saturation, at which the enzyme is working at maximum velocity (vmax) and the addition of ____ will not change v

A

[S]

57
Q

A reaction cannot go any faster once it’s reached ____

A

saturation

58
Q

At saturation, the enzyme is working at ____

A

maximum velocity ( v max)

59
Q

At saturation, the only way to increase v max is to ____

A

Increase enzyme concentration

60
Q

when the reaction rate is equal to half of Vmax, ___ = ____

A

Km = [S]

61
Q

Define Km

A

the substrate concentration at which half of the enzyme’s active sites are full

62
Q

High Km indicates ___

A

low affinity for substrate

63
Q

Low Km indicates ___

A

high affinity for substrate

64
Q

Define Kcat

A

Number of substrate molecules converted to product per enzyme molecule per second

65
Q

Define Lineweaver-Burk plot

A

Double reciprocal graph of the Michaelis-Menten equation

66
Q

Define Michaelis-Menten plot

A

Plot showing that as substrate increases the rate of reaction increases, until plateauing at vmax

67
Q

When would an enzyme demonstrate a sigmoid curve on a Michaelis-Menten plot?

A

When demonstrating cooperativity among substrate binding sites

68
Q

Phosphofructokinase-1 is an example of a regulatory enzyme demonstrating ____

A

Cooperativity

69
Q

Define Hill’s coefficient

A

A value that indicates the nature of cooperative binding

70
Q

If Hill’s coefficient >1, then ___

A

positively cooperative binding occurs so that after 1 ligand is bound the affinity of the enzyme for further ligands increase

71
Q

If Hill’s coefficient is < 1, then ____

A

negatively cooperative binding occurs so that after 1 ligand is bound the affinity of the enzyme for further ligands decreases

72
Q

If Hill’s = 1, then _____

A

the enzyme does not exhibit cooperative binding

73
Q

During cooperative binding, when a substrate binds, subunits transition from the ___ state to the ___ state

A

Tense (T); relaxed (R)

74
Q

What is the optimum temperature of an enzyme in the human body?

A

37C (98.6F and 310K)

75
Q

What is the optimum pH for most enzymes in the human body?

A

7.4

76
Q

Most enzymes in the human body are optimal at a pH of 7.4; what enzymes are the exception, where can you find them, and at what pH do they work?

A

Pepsin, in the stomach, at pH 2; pancreatic enzymes, in the small intestine, at pH 8.5

77
Q

How does salinity effect enzymes?

A

In vitro; disrupt H and ionic bonds, causing denaturation

78
Q

Define feedback regulation

A

Molecules further down a metabolic pathway that regulate enzymes higher up the pathway

79
Q

Define feedforward regulation

A

Intermediate molecules in a metabolic pathway that regulate enzyme higher up in the pathway

80
Q

List the 4 types of reversible inhibition

A

1) competitive
2) noncompetitive
3) mixed
4) uncompetitive

81
Q

Define competitive inhibition

A

A type of reversible inhibition in which the inhibitor binds to the same active site as the substrate

82
Q

How can competitive inhibition be overcome?

A

By adding more substrate

83
Q

Competitive inhibition doesn’t impact ___ but does increase ___

A

Vmax; Km

84
Q

Define noncompetitive inhibition

A

A type of reversible inhibition in which the inhibitor binds to the allosteric site, causing conformational change in the enzyme

85
Q

Noncompetitive inhibition decreases ___ but does not change ____

A

Vmax, Km

86
Q

Define mixed inhibition

A

A type of reversible inhibition in which an inhibitor binds equally to the allosteric site on an enzyme or enzyme-substrate complex with a different affinity for each

87
Q 
Which type of reversible inhibition binds to both the enzyme and enzyme-substrate complex?
A) competitive inhibition
B) noncompetitive inhibition
C) mixed inhibition
D) uncompetitive inhibition
A

A and B

88
Q

_____ inhibitors have an equal affinity for the enzyme and enzyme-substrate complex

A

Noncompetitive

89
Q

Mixed inhibition decreases ___ and can increase or decrease ___

A

Vmax; Km

90
Q

When would mixed inhibition cause Km to increase

A

If the inhibitory preferentially binds to the enzyme

91
Q

When would mixed inhibition cause Km to decrease

A

If the inhibitor preferentially binds to the enzyme-substrate complex

92
Q

Define uncompetitive inhibition

A

A type of reversible inhibition in which an inhibitor binds to the allosteric site of an enzyme-substrate complex and prevents the release of the substrate from the enzyme

93
Q

Uncompetitive inhibition lowers ___ and ___

A

Vmax; Km

94
Q

How does competitive inhibition effect Vmax and Km?

A

Does not effect Vmax; increases Km

95
Q

How does noncompetitive inhibition effect Vmax and Km?

A

Decreases; does not effect Km

96
Q

How does mixed inhibition effect Vmax and Km?

A

Vmax decreases; Km increases or decreases

97
Q

How does uncompetitive inhibition effect Vmax and Km?

A

Decreases Vmax; decreases Km

98
Q

Define irreversible inhibition

A

The binding of an inhibitor that causes permanent conformation change to the enzyme or when the active site is occupied by the inhibitor for a long time

99
Q

Allosteric enzymes shift between what two forms?

A

Active and inactive forms

100
Q

Enzymes can be covalently modified to by activated or deactivated by what two mechanisms?

A

phosphorylation or glycosylation

101
Q

Define glycosylation

A

Covalent attachment of sugar moieties; can tag an enzyme to be transported with a cell or modify protein activity and selectivity

102
Q

Define zymogen

A

inactive forms of enzymes that have a regulatory site preventing the catalytic domain from being bound by the substrate

103
Q

Trypsinogen is an example of what form of enzyme?

A

Zymogen

104
Q

Define caspases

A

Apoptotic enzymes

105
Q

Most zymogens have the suffix ___

A

-ogen

106
Q

Digestive enzymes are typically examples of what form of enzyme and why>

A

Zymogens; we want to wait for the enzymes to be activated only when it’s time to digest food so that the enzymes don’t digest the stomach lining

MCAT (13 decks)

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