Enzymes And Bioenergetics Flashcards
0
Q
Physically distinct versions of a given enzyme, each of which catalyzes the same reaction
A
Isozymes
1
Q
Protein catalysts that increase the velocity of a chemical reaction and are not consumed during the reaction they catalyze
A
Enzymes
2
Q
Catalyze oxidations and reductions
A
Oxidoreductases
3
Q
Catalyze transfer of moieties such as glycosyl, methyl, or phosphoryl groups
A
Transferases
4
Q
Catalyze hydrolytic cleavage of C-C, C-O, C-N and other bonds
A
Hydrolases
5
Q
Catalyze cleavage of C-C, C-O, C-N and other bonds by atom elimination, leaving double bonds
A
Lyases
6
Q
Catalyze geometric or structural changes within a molecule
A
Isomerases
7
Q
Catalyze the joining together of two molecules coupled to the hydrolysis of ATP
A
Ligases
8
Q
Properties of Enzymes
A
Contain an active site Highly efficient Highly specific Require cofactors Compartmentalized Can be regulated or inhibited
9
Q
Distinguished by their tight, stable incorporation into protein’s structure by covalent or noncovalent forces
A
Prosthetic Group
10
Q
Bind in transient, dissociable manner either to the enzyme or to a substrate
A
Cofactor
11
Q
Serve as recyclable shuttles or group transfer agents that transport many substrates from their point of generation to their point of utilization
A
Coenzyme
12
Q
How enzymes work?
A
Lower free energy of activation
Do not change the energy of the reactants and products and the equilibrium of the reaction
13
Q
Describes how reaction velocity varies with substrate concentration
A
Michaelis-Menten Equation
14
Q
Enzymes that follow Michaelis-Menten Kinetics have a
A
Hyperbolic curve
15
Q
Allosteric reactions have
A
Sigmoid curve
16
Q
Low substrate affinity =
A
High Km
17
Q
High substrate affinity =
A
Low Km
18
Q
Factors that affect the reaction rate
A
Substrate concentration
Temperature
pH
19
Q
Zero Order Kinetics
Rate not affected by substrate concentration
A
Above Km
20
Q
First Order Kinetics
Rate directly proportional to substrate concentration
A
Below Km
21
Q
High Temperature =
A
Increased reaction rate
22
Q
Extremely High Temperature =
A
Decreased reaction rate (due to denaturation)
23
Q
pH Extremes =
A
Decreased reaction rate (due to denaturation)
24
Reciprocal of the Michaelis-Menten Equation; Used to calculate Km and Vmax as well as to determine the mechanism of action of enzyme inhibitors
Lineweaver-Burk Plot
25
Any substance that can diminish the velocity of an enzyme-catalyzed reaction
Enzyme inhibitor
26
Inhibitor is shaped similar to substrate and competes for binding site; Increase substrate, Increased Km, Vmax Not changed
Competitive Inhibitor
27
Inhibitor binds to enzyme somewhere other than the active site and halts catalysis; Increased enzyme, Km Not changed, Vmax Lowered
Noncompetitive Inhibitor
28
Regulation of Enzyme Activity
Change in substrate concentration
Through allosteric binding sites
Through covalent modification of the enzyme
Through induction and repression of enzyme synthesis
29
The substrate itself serves as an effector
Homotropic Effectors
30
The effector is different from the substrate
Heterotropic Effectors
31
Serum Enzyme: Aspartate aminotransferase
Myocardial infarction
32
Serum Enzyme: Alanine aminotransferase
Viral hepatitis
33
Serum Enzyme: Amylase
Acute pancreatitis
34
Serum Enzyme: Ceruloplasmin
Hepatolenticular degeneration (Wilson's disease)
35
Serum Enzyme: Creatine kinase
Muscle disorders and Myocardial infarction
36
Serum Enzyme: Gamma-Glutamyl transpeptidase
Various liver diseases
37
Serum Enzyme: Lactate dehydrogenase (isozymes)
Myocardial infarction
38
Serum Enzyme: Lipase
Acute pancreatitis
39
Serum Enzyme: Phosphatase, acid
Metastatic carcinoma of the prostate
40
Serum Enzyme: Phosphatase, alkaline (isozymes)
Various bone disorders, obstructive liver diseases
41
Transfer and utilization of energy in biologic systems
Bioenergetics
42
Measure of heat content of the reactants and products; Measure in joules
Enthalpy (
43
Measure of the change in randomness or disorder of the reactants and products; Measured in joules/Kelvin
Entrophy (
44
Amount of energy that can be used;
Change in Free Energy (
45
Standard Free Energy Change
46
Net loss of energy (Exergonic)
| (+) Spontaneous Reaction
47
Net gain of energy (Endergonic)
| (-) Spontaneous Reaction
48
Same (Equilibrium)
| Forward and Backward Reactions Equal
49
(-) Enthalpy (+) Entropy =
Always Spontaneous Reaction
50
(+) Enthalpy (-) Entropy =
Always No Spontaneous Reaction
51
(+) Enthalpy (+) Entropy =
Maybe Spontaneous Reaction, but only at High Temp
52
(-) Enthalpy (-) Entropy =
Maybe Spontaneous Reaction, but only at Low Temp
53
Adenosine molecule to which three phosphate groups are attached; Acts as the "energy currency" of the cell, transferring free energy derived from substances of higher energy potential to those of lower energy potential
Adenosine Triphosphate
54
Any
Used to make ATP
55
Any
Made from ATP
56
How ATP is produced?
Phosphate transfer
| Oxidative phosphorylation
57
Sources of High Energy Phosphorylation
Oxidative Phosphorylation
| Substrate Level Phosphorylation
58
Aerobic; The greatest quantitative source of high energy phosphate in aerobic organisms; Free energy comes from successive oxidation of substances in the respiratory chain within mitochondria; Molecular oxygen is the final substance to be reduced
Oxidative Phosphorylation
59
Anaerobic; Done through coupling reactions where a phosphate group is transferred to ADP from another substance with higher
Substrate Level Phosphorylation
60
In Glycolysis: ATP is generated in 2 steps
1,3-BPG + ADP ➡️3-PG + ATP (phosphoglycerate kinase)
| PEP + ADP ➡️pyruvate + ATP (pyruvate kinase)
61
In Citric Acid Cycle: ATP is generated in 1 step
Succinyl CoA + ADP➡️succinate + ATP (succinyl thiokinase)
62
Final common pathway by which electrons from different fuels of the body flow to oxygen; Occurs in inner mitochondrial membrane
Electron Transport Chain
63
2 electron carriers used in ETC:
Nicotinamide Adenine Dinucleotide (NAD+) - from Vit. B3 (Niacin)
Flavin Adenine Dinucleotide (FAD) - from Vit. B2 (Riboflavin)
64
Parts of ETC: Complex I
NADH dehydrogenase
65
Parts of ETC: Complex II
Succinate dehydrogenase (actually part of Krebs Cycle)
66
Parts of ETC: Coenzyme Q
A lipid, aka Ubiquinone
| Only non-protein part of ETC
67
Parts of ETC: Complex III
Cytochrome b/c1 (Fe/heme protein)
68
Parts of ETC: Cytochrome C
Fe/Heme protein, mobile part of ETC
69
Parts of ETC: Complex IV
Cytochrome a/a3 (Cu/heme protein) aka Cytochrome oxidase
70
What you have to remember about ETC?
1) Protons (H+) are pumped to the intermembranous space to create a gradient in 3 complexes: Complex I-NADH and flavoprotein, Complex III-Cytochrome B & C, Cytochrome IV-Cytochrome C & a+a3
2) All components are fixed to the inner mitochondrial membrane EXCEPT Coenzyme Q/Ubiquinone, Cytochrome C
3) Final electron acceptor is Oxygen
71
From oxidation of components in the respiratory chain is coupled to the translocation of Hydrogen ions (protons/H+); H+ moved from the inside to the outside of the inner mitochondrial membrane where it accumulates in the intermembranous space
Mitchell's Chemiosmotic Theory
72
ETC generates an electrical gradient and a pH gradient across the inner mitochondrial membrane; Protons driven towards mitochondrial matrix; Results in the synthesis of ATP
Oxidative Phosphorylation
73
2 components of ATP synthase
F1 - generates ATP from ADP + Pi
| F2 - channel where protons pass through
74
Deprives the ETC of sufficient oxygen, decreasing the rate of ETC and ATP production
Tissue Hypoxia
75
Stops electron flow from substrate to oxygen
Inhibitors of ETC
76
ETC Inhibitors: Complex I
Barbiturate
Piericidin A
Amytal
Rotenone
77
ETC Inhibitors: Complex II
Malonate
Carboxin
TTFA
78
ETC Inhibitors: Complex III
Antimycin A
| Dimercaprol
79
ETC Inhibitors: Complex IV
Cyanide
Carbon monoxide
Sodium azide
Hydrogen sulfide
80
Increase the permeability of the inner mitochondrial membrane to protons; Increased oxygen consumption; Increased oxidation of NADH; Decreased ATP synthesis
Uncouplers
81
Examples of Synthetic Uncouplers
2,4 dinitrophenol
| Aspirin
82
Example of uncoupling proteins
Thermogenin
83
Directly inhibits mitochondrial ATP Synthase (Complex V); Proton gradient continues to rise but there is no "escape valve" for the protons; ETC eventually stops because the cytochromes can no longer pump protons into the intermembranous space
ATP Synthase Inhibitors
84
Example ATP Synthase Inhibitor
Oligomycin
85
Reactive Oxygen Species
```
Superoxide (O2-)
Hydrogen peroxide (H2O2)
Hydroxyl radical (OH-)
```
86
Unstable products that are formed as a by-product of ETC when molecular oxygen (O2) is partially reduced
Reactive Oxygen Species
87
Mutation in the circular mitochondrial chromosome; Maternally inherited
Mitochondrial Diseases
88
Mutation in the circular mitochondrial chromosome that encodes:
1) 13 proteins that comprise the major complexes of Oxidative Phosphorylation
2) 22 tRNAs
3) 2 rRNAs
89
Examples of Mitochondrial Disease: All Complexes
Fatal Infantile Mitochondrial Myopathy
90
Examples of Mitochondrial Disease: Complex I
MELAS (Mitochondrial Encephalopathy, Lactic Acidosis, and Stroke-like episodes)
91
Examples of Mitochondrial Disease: Complex II
Kearns-Sayre Syndrome
92
Examples of Mitochondrial Disease: Complex III
Leber's Hereditary Optic Neuropathy
93
Examples of Mitochondrial Disease: Complex IV
Leigh's Disease
| Ragged Red Muscle Fiber Disease
