Enzymology I Flashcards
1
Q
Lowers the activation energy in a reaction
A
Enzymes
2
Q
Enzymes makes the reaction _________ times faster than uncatalyzed reactions
A
106 to 1020
3
Q
Enzymes are made up of specialised proteins. T/F
A
T
4
Q
Enzyme during chemical reaction gets used up. T/F
A
F
5
Q
Not all enzymes are proteins. T/F
A
T
6
Q
all enzymes need cofactors to be activated. T/F
A
F
7
Q
● Protein part of an enzyme without cofactors or prosthetic groups
● Gives the 3-dimensional structure
A
Apoenzyme
8
Q
Catalytically inactive ❗️ and heat-labil
A
Apoenzyme
9
Q
● a.k.a cosubstrates
● Usually synthesized by vitamins
A
Coenzymes
10
Q
Is coenzyme monogamous or polygamous.
A
Poly
11
Q
most vitamins function as a coenzyme. T/F
A
T
12
Q
3 groups of cofactors
A
A. Coenzyme
B. Prosthetic Group
C. Metal Ions
13
Q
Small organic or inorganic molecules
● Soluble non-protein components needed by apoenzyme
for its activity
A
Cofactor
14
Q
Can cofactors undergo regeneration?
A
Yes
15
Q
2 types of vitamin deficiency
A
Functional deficiency
Dietary deficiency
16
Q
drugs and toxins that inhibits proteins required for coenzyme synthesis
A
Functional deficiency
17
Q
Dietary deficiency
A
inadequate intake of vitamin
18
Q
a.k.a Iron-sulfur clusters
● Inorganic molecules
A
Metal ions
19
Q
Metal ions are involved in what chemical rxn?
A
electron transfer reactions
20
Q
Is metal ions monogamous or polygamous?
A
Mono
21
Q
● Organic molecule
● Firmly and permanently attaches to an apoenzyme
(monogamous)
A
Prosthetic grp
22
Q
Classify the following based on the type of cofactors:
Biotin (B7)
A
Prosthetic group
23
Q
Classify the following based on the type of cofactors:
NAD+
A
Coenzyme - oxidation reduction coenzyme
24
Q
Classify the following based on the type of cofactor:
Pyridoxal phosphate (PLP),
A
Prosthetic group
25
Classify the following based on the type of cofactor:
Thiaminepyrophosphate (TPP), and lipoic acid
Prosthetic group
26
Apoenzyme + Cofactor
Holoenzyme
27
Completely catalytic active enzyme
Holoenzyme
28
● a.k.a Key Enzyme
● Catalyzes the rate-limiting or committed step
Regulatory enzyme
29
The rate limiting step is considered to be the _______ reaction in a metabolic process
Slowest
30
The site or region on an enzyme where substrates bind
and where the enzyme-substrate complex (ES complex)
forms, allowing it to catalyze a reaction
Active site
31
Active site is located in
Clefts and crevices
32
The surface of an enzyme is lined with functional groups and catalytic group. T/f
T
33
● Region that is physically separated from catalytic site of an
enzyme
● Where allosteric modifiers and effectors bind
Allosteric site
34
Goal of allosteric enzymes
To induce conformational change in the enzyme
35
___________ allosteric effectors: enhances activity of catalytic
site; stimulate the enzyme
Positive
36
___________ allosteric effectors: changes the conformation of
the active site to inhibit the activity of the enzyme
Negative
37
Term used for reactant
Substrate
38
Classifications of coenzyme
→ Activation-Transfer Coenzymes
→ Oxidation-Reduction Coenzymes
39
Oxidation-Reduction Coenzymes. Examples:
NAD+, FAD, Vit. E
40
Derived from Vitamin B5 (Pantothenic acid).
Coenzyme A (5 Yr old boy loves Apples)
41
Coenzyme A take part in what reactions
CAC, FA synthesis and oxidation, acylations and cholesterol synthesis.
42
→ α- Ketoglutarate → succinyl CoA
α- Ketoglutarate Dehydrogenase Complex Reaction
43
Pyruvate → Acetyl CoA
Pyruvate Dehydrogenase Complex
44
Derived from Vitamin B3 (Niacin)
NAD+ & NADP+
45
→ Catalyzes alcohols to ketones oxidation
→ Example: Lactate to pyruvate
NAD-dependent dehydrogenase:
46
NADP
reductive synthesis pathways
47
Thiamine pyrophosphate
● Derived from Vitamin B1 (Thiamine)
● Synthesized in human cells
48
Cofactor in energy-yielding metabolism
Thiamine pyrophosphate (TPP)
49
TPP has a carbon-reactive functional group which serves as a carrier of ketone groups in metabolism.
No. ALDEHYDE GROUP DAPAT
50
Special roles of TPP
→ Transketolase reaction in PPP
→ Oxidative decarboxylation reactions in CAC
→ Catabolism of the branched-chain amino acids
51
(Vitamin B7)
● Prosthetic group
Biotin
52
Cofactors of carboxylases
Biotin
53
Enzyme: pyruvate carboxylase
Role
Convert pyruvate to oxaloacetate. Primary substrate of gluconeogenesis.
54
Enzyme: Acetyl-CoA carboxylase
Role
→ Acetyl-CoA to Malonyl-CoA
▪ De Novo Synthesis of Fatty Acids
55
Active form of biotin
Active form: Biocytin
56
Derived from Vitamin B2 (Riboflavin)
FAD
57
Coenzyme of dehydrogenases
FAD
58
FAD is important in the following rxns:
CAC
Beta oxidation
Nitric oxide synthesis
59
FAD is a stronger oxidizing agent than NAD. T/F
T
60
Derived from Vitamin B6 (Pyridoxine)
Pyridoxal Phosphate (PLP)
61
Major cofactor in transamination reactions
PLP
62
PLP is important in the following:
Important in the following:
→ Heme synthesis
→ Transamination
→ Histamine synthesis
→ Neurotransmitter synthesis
63
Metal ions cofactor:
Carbonic anhydrase
Zn+2
64
Metal ions cofactor:
Hexokinase, pyruvate kinase, G6PD, Enolase, glycosyltransferase, phosphoglucomutase
Mg+2
65
Metal ions cofactor:
Lipase
Ca+2
66
Metal ions cofactor:
Urease
Ni+2
67
Metal ions cofactor:
Salivary amylase
Cl-
68
Metal ions cofactor:
Cytochrome oxidase
Catalase
Peroxidase
Fe+2
69
Metal ions cofactor:
Pyruvate kinase
Propionyl CoA carboxylase
K+
70
Cofactor of Hexokinase or Glucokinase
Mg2+
71
6 major classes of enzymes
H - Hydrolases
I - Isomerases
L - lyases
L - ligase
O - oxidoreductases
T - transaminases
72
Transfer of electrons and hydrogen atoms
OXIDOREDUCTASES
73
Transfer functional groups other than hydrogen (like C-, N-,
or P-) from donors to acceptors
● Utilizes 2 substrates to produce 2 products
TRANSFERASE
74
Catalyze cleavage of chemical bonds (ester, ether, peptide or glycosidic bonds) by addition of H2O, producing 2 products
HYDROLASES
75
All digestive enzymes are hydrolases. T/f
T
76
Cleaves C-C, C-O, C-N bonds by means other than hydrolysis or oxidation (no addition of H2O)❗
LYASES
77
Rearrange bond structure of a compound 📖[Marks]
● Catalyze the transfer of functional groups or double bonds
within the same molecule or catalyze racemization of
optical or geometric isomers
ISOMERASES
78
Catalyze ligation or joining of 2 substrates with covalent
bonds
LIGASES
79
Classify type of enzyme:
Dehydrogenase
Oxidoreductase
80
Classify type of enzyme:
Kinases
Transferase
81
Classify type of enzyme:
Peroxidases
Oxidoreductase
82
Classify type of enzyme:
Esterases
Hydrolases
83
Classify type of enzyme:
Thiolases
Hydrolases
84
Classify type of enzyme:
Decarboxylases
Lyases
85
Classify type of enzyme:
Aldolases
Lyases
86
Classify type of enzyme:
L-alanine to D-alanine
Isomerases
87
Classify type of enzyme:
Pyruvate carboxylase
Ligases
88
Classify type of enzyme:
DOPA decarboxylase
Lyases
89
Cleaves C-C bond and released as CO2, DOPA is decarboxylated as Dopamine❗
DOPA decarboxylase
90
Lyases generate either a double bond or a ring structure but DO NOT ALWAYS generate a double bond. T/F
T
91
Transfers the functional group phosphate from ATP to anacceptor molecule❗
Kinases
92
Glucose to G6PD is highly spontaneous thus it is what type of rxn? Endergonic or exergonic?
Exergonic
93
Addition of H2O to a substrate
Hydratase
94
First step in gluconeogenesis
Pyruvate carboxylase
95
Enzymes Can be temporarily changed or modified during reaction. T/F
T
96
Enzymes are generated or recycled or return to their original
form. T/F
T
97
ENZYMES INCREASE REACTION RATES BY DECREASING ACTIVATION ENERGY. T/F
T
98
Axis where reaction progress that represents progressive bond breakage/ formation
X axis
99
Axis where free energy, ΔG
Y axis
100
→ rate limiting step of the overall reaction
→ has a higher free energy than either substrate or
product
Transition state (S=/)
101
→ rate limiting step of the overall reaction
Transition state
102
Activation energy =/
difference in free energy between the transition state and substrate
103
represents the difference between the energies of the reactants and the energies of the products
Activation energy
104
formation of the transition state from substrate is endergonic or exergonic?
Endergonic
105
If the transition from substrate to transition state is endergonic, what is the overall reaction?
Exergonic
106
enzyme catalyzes only on a single chemical reaction. T/F
T
107
Catalyzes only one reaction.
Absolute Specificity.
Examples: Carbonic Anhydrase, Catalase, Glucokinase
108
highly specific for glucose
Glucokinase
109
Can catalyze the phosphorylation of the hexoses glucose, galactose and mannose.
Group Specificity
110
Recognizes only the L-isomer of lactate but not the D-isomer
Stereospecificity
Example: lactate dehydrogenase
111
Most Enzymes are made up of proteins. Therefore they are bonded by peptide bonds. T/F
T
112
unfolding of proteins with the use of acid or base, chaotropic agents or detergents
Denaturation
113
thermal denaturation of the enzyme is reversible or irreversible?
Irreversible
114
What occurs in vmax?
all enzymes have been saturated (all enzymes have been “partnered” with a substrate)
115
When the rxn reaches vmax, does this represent the E-S complex?
Yes
116
rate of chemical reaction
Reaction velocity
117
Competitive Inhibition
Inhibitor binds to ENZYME to block substrate.
118
Non-Competitive Inhibition
Inhibitor binds to SUBSTRATE. Binding could still occur but there is decreased catalytic activity due to conformational change.
119
substrate binds to a site whose shape complements its own.
Lock and Key Model
120
Lock and Key Model is developed by
Fischer
121
does not take into account the 3-dimensional flexibility of
proteins → the key acts on the lock but not vice versa
→ Enzymes are not rigid or static structures, the lock
should also act on the key
Lock and key
122
substrate and enzyme fit only at binding ❗.
Enzyme undergoes a slight conformational change
(“induced fit”) on binding to the substrate
Koshlands induce fit model
123
Enzyme forms a complementary shape or flexible pocket that approximates substrate’s shape
Induce fit model
124
The induct fit model is induced by what bond
Hydrogen bond
125
The Michaelis-Menten constant Km represents which of
the following kinetic relationships?
A. Dissociation constant of the ES complex.
B. [Substrate] at Vmax.
C. [Substrate] at Vmax/2.
D. Vmax at highest [substrate]
C
126
Which of the following is the catalytically active
enzyme?
A. Coenzyme
B. Holoenzyme
C. Metal ion
D. Prosthetic group
B
127
Denaturation is an effect of which factor affects the
activity of HMG CoA reductase?
A. Cofactor
B. pH
C. Substrate concentration
D. Temperature
D
128
Which of the following is TRUE about the
characteristics/attributes of HMG CoA reductase as a
rate-limiting enzyme?
A. Activity is not affected by a number of allosteric
molecules.
B. Catalyzes the first irreversible step of a metabolic
pathway.
C. Catalyzes the slowest reaction in a multi-step
pathway.
D. Favors a highly spontaneous and irreversible
reaction.
C
129
How does Atorvastatin® as a competitive inhibitor of
HMG CoA reductase decrease cholesterol synthesis?
A. Binds to the active site of the enzyme.
B. Binds to the allosteric site of the enzyme.
C. Promotes the inactivation of the enzyme.
D. Increases the Km of the enzyme.
A
130
Which regulatory mechanism affects HMG CoA
reductase activity in a patient with
hypercholesterolemia?
A. Allosteric (Non Covalent modification)
B. Feedback inhibition
C. Induction or repression of enzyme synthesis
D. Reversible covalent modification
E. Zymogen activation
B
131
Catalyze cleavage of high-energy phosphate bond of
pyrophosphate (PPi) in the presence of H2O, forming 2
inorganic phosphates (2 Pi)
Pyrophosphatase
132
a substance that mediates inflammatory and allergic conditions
Histamine
133
Histidine decarboxylase
Catalyzes the removal of carboxyl group of histidine to
produce histamine in the presence of PLP as a cofactor
134
Catalyzes transfer of OH at the left side of carbon 3 of
D-xylulose 5-phosphate to the right side, forming
D-ribulose 5-phosphate
Epimerase
