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M1 > Enzymes > Flashcards

Enzymes Flashcards

1
Q

Proteolytic enzymes catalyze the hydrolysis of ______

A

peptide bonds

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2
Q

Most proteolytic enzymes also catalyze the hydrolysis of an _____

A

Ester bond

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3
Q

An inactive enzyme without its cofactor protein part of a holoenzyme

A

apoenzyme

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4
Q

Requires a tightly bound meta ion

A

Metalloenzymes

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5
Q

Consequence of Thiamine (B1) deficiency

A

Beriberi (weight loss, heart problems, neurological dysfunction)

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6
Q

Consequence of Riboflavin (B2) deficiency

A

Cheliosis and angular stomatitis (lesions of the mouth), dermatitis

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7
Q

Consequence of Pyridoxine (B6) deficiency

A

Depression, confusion, convulsions

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8
Q

Consequence of niacin deficiency

A

Pellagra

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9
Q

Consequence of Pantothenic acid deficiency

A

Hypertension

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10
Q

Consequence of Biotin deficiency

A

Rash about the eyebrows, muscle pain, fatigue (rare)

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11
Q

Consequence of folic acid deficiency

A

Anemia, neural-tube defects in development

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12
Q

Consequence of B12 deficiency

A

Anemia, pernicious anemia, methylmalonic acidosis

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13
Q

Roles in vision, growth, and reproduction

A

Vitamin A Deficiencies include: night blindness, cornea damage, damage to respiratory and GI tract

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14
Q

Antioxidant vitamin

A

Vitamin C (ascorbic acid) Deficiencies include: scurvy (swollen and bleeding gums, subdermal hemorrhaging); Vitamin E Deficiencies include: Inhibition of sperm production; lesions in muscles and nerves (rare)

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15
Q

Vitamin in charge of regulation of calcium and phosphate metabolism

A

Vitamin D Deficiencies include: Rickets (children): skeletal deformaties, impaired growth, Osteomalacia (adults): soft bending bones

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16
Q

Vitamin that regulates blood coagulation

A

Vitamin K Deficiencies include: subdermal hemorrhaging

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17
Q

Oxidoreductases

A

Act on many chemical groupings to add or remove hydrogen atoms

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18
Q

Transferases

A

Transfer functional groups between donor and acceptor molecules. Kinases are specialized transferases that regulate metabolism by transferring phosphate from ATP to other molecules

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19
Q

Hydrolases

A

Add water across a bond, hydrolyzing it

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20
Q

Lyases

A

Add water, ammonia or carbon dioxide across double bonds, or remove these groups to produce double bonds

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21
Q

Isomerases

A

Carry out many kinds of isomerization: L to D isomerization, mutase reactions (shifts of chemical groups) and others

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22
Q

Ligases

A

Catalyze reactions in which two chemical groups are joined or ligated using energy from ATP

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23
Q

Enzyme exhibit a very high degree of

A

specificity

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24
Q

1+ inorganic ions, such as Fe2+, Mg2+, Mn2+, or Zn2+

A

cofactor

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25
Q

complex organic or metalloorganic molecule that act as transient carriers of specific functional groups

A

coenzyme

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26
Q

coenzyme or metal ion that is very tightly or covalently bound to the enzyme protein

A

prosthetic group

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27
Q

complete catalytically active enzyme together with its bound coenzyme and/or metal ions

A

holoenzyme

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28
Q

Translocases

A

Movement of molecules or ions across membranes or their separation within membranes

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29
Q

The molecule that is bound to the active site and acted upon by the enzyme

A

substrate

30
Q

difference between the ground state energy level and the transition state energy level

A

activation energy

31
Q

catalysts _____the activation energy and ______ the reaction rate

A

lower, increase

32
Q

under standard conditions K’eq=

A

[P]/[S]

33
Q

K’eq has a ______ relationship to Delta G’

A

Inverse

34
Q

for a unimolar reaction S –> P a rate equaction expresses the rate of reaction and V =

A

V=k[S] where V is the velocity of the reaction and [S] is the concentration of the substrate

35
Q

first-order reaction = rate depends only on the

A

concentration of S

36
Q

Second-order reactions V=

A

V=k[S1][S2]

37
Q

covalent interactions between enzymes and substrate _____the activation energy

A

lower

38
Q

barrier to reaction, Delta G (activation energy) includes:

A

the entropy of molecules in solution the solvation shell of hydrogen-bonded water that surrounds and stabilizes most biomolecules in aqueous solution the distortion of substrates that must occur in many reactions the need for proper alignment of catalytic functional groups on the enzyme

39
Q

replacement of the solvation shell of structured water around the substrate with weak bonds between substrate and enzyme

A

desolvation replaces most or all hydrogen bonds between the substrate and water

40
Q

mechanism by which the enzyme itself undergoes a conformational change when the substrate binds, induced by multiple weak interactions with the substrate

A

induced fit enhances catalytic properties

41
Q

catalytic functional groups aid in the cleavage and formation of bonds by a variety of mechanisms:

A

general acid-base catalysis covalent catalysis metal ion catalysis

42
Q

Metal Ion Catalysis

A

help orient the substrate for reaction stabilize charged reaction transition states mediate oxidation-reduction reactions by reversible changes in the metal ion’s oxidation state

43
Q

initial transient period during which ES builds up

A

pre–steady state

44
Q

period during which [ES] and other intermediates remain constant

A

steady state

45
Q

the traditional analysis of reaction rates

A

steady-state kinetics

46
Q

Michaelis-Menten equation

A

V0 = Vmax [S] /Km + [S]

where V0 is the initial velocity, Vmax is the maximum velocity, [S] is the initial substrate concentration, and Km is a constant called the Michaelis constant

47
Q

Km = [S] when

A

when V0 = ½Vmax

48
Q

Lineweaver-Burk equation

A

1/V0 = Km + [S]/Vmax[S]

49
Q

for a two-step Michaelis-Menten mechanism

A

Vmax = k2[Et]

50
Q

•the rate constant for the conversion of E + S to E + P

A

specificity constant

51
Q

the first substrate is converted to product and dissociates before the second substrate binds

A

example: Ping-Pong, or double-displacement, mechanism

52
Q
A
53
Q

What nomenclature is this

A
54
Q

Intersecting Lines Indicate the Formation of a

A

Ternary Complex

55
Q

Parellel lines indicate a ____________ pathway

A

Ping-pong (Double-Displacement)

56
Q

for an enzyme where product release,_________ , is rate-limiting

A

EP → E + P ; (k3 is rate-limiting):

57
Q

types of reversible inhibition

A
  • competitive inhibition
  • uncompetitive inhibition
  • mixed inhibition
  • noncompetitive inhibition
58
Q

competes with substrate for active site of an enzyme; type of reversible inhibition; Km increases but Vmax is unchanged

A

competitive inhibition

the Michaelis-Menten equation becomes

V0 = (Vmax[S]) /(αKm + [S])

where α = 1 + [I]/K1 and KI = ([E][I]) /[EI]

59
Q

What inhibition is indicated?

A

Competitive Inhibition

lines intersect at the y axis

60
Q

binds at a site distinct from the substrate active site; binds only to the ES comples; type of reversible inhibition; both Vmax and Km deceases

A

Uncompetitive Inhibitors

61
Q

What type of inhibition is depicted here?

A

Uncompetitive Inhibition

lines are parallel

62
Q

affects the Vmax but not the Km; special case of α = α′

A

Noncompetitive inhibition

63
Q

bind covalently with or destroy a functional group on an enzyme that is essential for the enzyme’s activity, or form a highly stable noncovalent association

A

irreversible inhibitor

64
Q

undergo the first few steps until it is converted into a compound that combines irreversibly with the enzyme

class of irreversible inhibitors

A

suicide inactivator = mechanism-based inactivators

65
Q

stable molecules designed to resemble transition states; type of irreversible inhibitors; bind to an enzyme more tightly than does the substrate in

A

transition-state analogs

66
Q

catalytic activity increases or decreases in response to certain signals

allows the cell to meet changing needs for energy and biomolecules

A

regulatory enzymes

67
Q

Modulation of Regulatory Enzyme

A
  • allosteric enzymes = function through reversible, noncovalent binding of regulatory compounds called allosteric modulators or allosteric effectors (small metabolites or cofactors)
  • reversible covalent modification
  • binding of separate regulatory proteins
  • removal of peptide segments by proteolytic cleavage
68
Q

regulation in which the substrate and modulator are identical

A

homotrophic

69
Q

regulation in which the modulator is a molecule other than the substrate

A

heterotropic

70
Q

catalyzes the formation of carbamoyl aspartate, an early step in pyrimidine biosynthesis:

A

aspartate transcarbamoylase (ATCase)

71
Q

The Kinetic Properties of Allosteric Enzymes Diverge from Michaelis-Menten Behavior

A

plots of V0 versus [S] usually produce a sigmoid saturation curve, rather than a hyperbolic curve

[S]0.5 or K0.5 represents the [S] giving half-maximal velocity of the reaction

72
Q
A

M1 (48 decks)

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