Enzymes

Question 1

Proteolytic enzymes catalyze the hydrolysis of ______

Answer 1

peptide bonds

Question 2

Most proteolytic enzymes also catalyze the hydrolysis of an _____

Answer 2

Ester bond

Question 3

An inactive enzyme without its cofactor protein part of a holoenzyme

Answer 3

apoenzyme

Question 4

Requires a tightly bound meta ion

Answer 4

Metalloenzymes

Question 5

Consequence of Thiamine (B1) deficiency

Answer 5

Beriberi (weight loss, heart problems, neurological dysfunction)

Question 6

Consequence of Riboflavin (B2) deficiency

Answer 6

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

Question 7

Consequence of Pyridoxine (B6) deficiency

Answer 7

Depression, confusion, convulsions

Question 8

Consequence of niacin deficiency

Answer 8

Pellagra

Question 9

Consequence of Pantothenic acid deficiency

Answer 9

Hypertension

Question 10

Consequence of Biotin deficiency

Answer 10

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

Question 11

Consequence of folic acid deficiency

Answer 11

Anemia, neural-tube defects in development

Question 12

Consequence of B12 deficiency

Answer 12

Anemia, pernicious anemia, methylmalonic acidosis

Question 13

Roles in vision, growth, and reproduction

Answer 13

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

Question 14

Antioxidant vitamin

Answer 14

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)

Question 15

Vitamin in charge of regulation of calcium and phosphate metabolism

Answer 15

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

Question 16

Vitamin that regulates blood coagulation

Answer 16

Vitamin K Deficiencies include: subdermal hemorrhaging

Question 17

Oxidoreductases

Answer 17

Act on many chemical groupings to add or remove hydrogen atoms

Question 18

Transferases

Answer 18

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

Question 19

Hydrolases

Answer 19

Add water across a bond, hydrolyzing it

Question 20

Lyases

Answer 20

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

Question 21

Isomerases

Answer 21

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

Question 22

Ligases

Answer 22

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

Question 23

Enzyme exhibit a very high degree of

Answer 23

specificity

Question 24

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

Answer 24

cofactor

Question 25

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

Answer 25

coenzyme

Question 26

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

Answer 26

prosthetic group

Question 27

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

Answer 27

holoenzyme

Question 28

Translocases

Answer 28

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

Question 29

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

Answer 29

substrate

Question 30

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

Answer 30

activation energy

Question 31

catalysts \_\_\_\_\_the activation energy and ______ the reaction rate

Answer 31

lower, increase

Question 32

under standard conditions K'eq=

Answer 32

[P]/[S]

Question 33

K'eq has a ______ relationship to Delta G'

Answer 33

Inverse

Question 34

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

Answer 34

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

Question 35

first-order reaction = rate depends only on the

Answer 35

concentration of S

Question 36

Second-order reactions V=

Answer 36

V=k[S1][S2]

Question 37

covalent interactions between enzymes and substrate \_\_\_\_\_the activation energy

Answer 37

lower

Question 38

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

Answer 38

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

Question 39

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

Answer 39

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

Question 40

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

Answer 40

induced fit enhances catalytic properties

Question 41

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

Answer 41

general acid-base catalysis covalent catalysis metal ion catalysis

Question 42

Metal Ion Catalysis

Answer 42

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

Question 43

initial transient period during which ES builds up

Answer 43

pre–steady state

Question 44

period during which [ES] and other intermediates remain constant

Answer 44

steady state

Question 45

the traditional analysis of reaction rates

Answer 45

steady-state kinetics

Question 46

Michaelis-Menten equation

Answer 46

V₀ = V_max [S] /K_m + [S] where V₀ is the initial velocity, V_max is the maximum velocity, [S] is the initial substrate concentration, and K_m is a constant called the Michaelis constant

Question 47

Km = [S] when

Answer 47

when V₀ = ½Vmax

Question 48

Lineweaver-Burk equation

Answer 48

1/V₀ = K_m + [S]/V_max[S]

Question 49

for a two-step Michaelis-Menten mechanism

Answer 49

V_max = k₂[E_t]

Question 50

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

Answer 50

specificity constant

Question 51

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

Answer 51

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

Question 52

Answer 52

Question 53

What nomenclature is this

Answer 53

Question 54

Intersecting Lines Indicate the Formation of a

Answer 54

Ternary Complex

Question 55

Parellel lines indicate a ____________ pathway

Answer 55

Ping-pong (Double-Displacement)

Question 56

for an enzyme where product release,\_\_\_\_\_\_\_\_\_ , is rate-limiting

Answer 56

EP → E + P ; (k3 is rate-limiting):

Question 57

types of reversible inhibition

Answer 57

* competitive inhibition * uncompetitive inhibition * mixed inhibition * noncompetitive inhibition

Question 58

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

Answer 58

competitive inhibition the Michaelis-Menten equation becomes V₀ = (Vmax[S]) /(αKm + [S]) where α = 1 + [I]/K₁ and K_I = ([E][I]) /[EI]

Question 59

What inhibition is indicated?

Answer 59

Competitive Inhibition ## Footnote lines intersect at the y axis

Question 60

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

Answer 60

Uncompetitive Inhibitors

Question 61

What type of inhibition is depicted here?

Answer 61

Uncompetitive Inhibition lines are parallel

Question 62

affects the V_max but not the K_m; special case of α = α′

Answer 62

Noncompetitive inhibition

Question 63

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

Answer 63

irreversible inhibitor

Question 64

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

Answer 64

suicide inactivator = mechanism-based inactivators

Question 65

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

Answer 65

transition-state analogs

Question 66

catalytic activity increases or decreases in response to certain signals allows the cell to meet changing needs for energy and biomolecules

Answer 66

regulatory enzymes

Question 67

Modulation of Regulatory Enzyme

Answer 67

* 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

Question 68

regulation in which the substrate and modulator are identical

Answer 68

homotrophic

Question 69

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

Answer 69

heterotropic

Question 70

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

Answer 70

aspartate transcarbamoylase (ATCase)

Question 71

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

Answer 71

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