ENZYMES Flashcards
1
Q
Proteins that act as catalysts for biochemical reactions, increasing the rate of reaction by lowering the energy of activation without being consumed in the process.
A
Enzymes
2
Q
The first identified enzyme that converted starch to sugar
A
Diastase
3
Q
modulates an enzyme activity
A
Effectors
4
Q
are found in animal and plant cells. It is needed to speed up the breakdown of hydrogen peroxide and breaks it down to oxygen and water.
A
Catalase
5
Q
Synthesizes starch by combining multiple glucose-1-phosphate molecules
A
Potato phosphorylase
6
Q
It allows enzymes to significantly accelerate biochemical reactions, making them 10^3 to 10^17 times faster than uncatalyzed reactions
A
Catalytic Efficiency
7
Q
The ability of an enzyme to interact with one or a few specific substrates and catalyze only one type of chemical reaction
A
Specificity
8
Q
Mild reaction conditions
A
37℃, physiological pH, ambient atmospheric pressure.
9
Q
Part of the enzyme where the reactants bind and where the biochemical reaction occurs
A
Active site
10
Q
The enzyme active site is usually composed of :
A
amino acid side chains interact, metal ions, various types of polar, non-polar, ionic interactions
11
Q
Found in saliva and the pancreas, breaks down starch into maltose.
A
Amylase
12
Q
The active site is a region within an enzyme that fits the shape of molecules called ___
A
substrates/reactants.
13
Q
Describes how substrates fit into the active site of an enzyme
A
The ‘Lock and Key Model’
14
Q
Additional non-protein molecules needed by some enzymes to help the reaction
A
Cofactors
15
Q
anything that is covalently bonded to an enzyme
A
Prosthetic group
16
Q
apoenzyme and the nonprotein part
A
Holoenzyme
17
Q
present in trace amounts within the enzyme.
A
Metal ions
18
Q
Zn 2+ a cofactor for
A
carboxypeptidase
19
Q
non-protein or organic, maybe a vitamin
A
Coenzyme
20
Q
Enzymes that catalyze the same reaction in different tissues of the body.
A
Isoenzymes
21
Q
converts lactate to pyruvate consists of five isoenzymes.
A
Lactate Dehydrogenase
22
Q
have slight variations in the amino acid sequences of the subunits of their quaternary structure.
A
Isoenzymes
23
Q
developed the four-integer number system and a name
A
Enzyme Commission
24
Q
six major classes of enzyme-catalyzed reactions
A
Oxidoreductases
Transferases
Hydrolases
Lyases
Isomerases
Ligases.
25
Enhances reaction rates by holding two molecules in close proximity to each other
Facilitation of Proximity
26
Involves the transient covalent bonding of the substrate to an amino acid residue in the active site
Covalent Catalysis
27
This mechanism involves the transient covalent bonding of the _____ to an amino acid residue in the__& . Generally, this is to the ____ group of a serine, although the side chains of ____, ____,____ ,____ , and ____can also be involved.
Substrate, active site, hydroxyl,threonine, cysteine, histidine, arginine, lysine
28
Amino acid residues act as weak acids or weak bases, stabilizing normally unstable charge intermediates.
General Acid-Base Catalysis
29
An enzyme that catalyzes the oxidation of alcohols
Alcohol Dehydrogenase
30
weak acids
weak bases
proton donors
proton acceptors
31
Accounts for the lowering of activation energy for a reaction
Binding Energy
32
A metal-substrate-enzyme complex can aid in the orientation of the substrate in the active site
Metal ions catalysis
33
Binding of the substrate distorts it in a way that facilitates the chemical reaction
Strain, Molecular Distortion, and Shape Change
34
Enzyme activity in body fluids reflects ___ status.
organ
35
Enzymes whose levels can increase following a heart attack
Creatine kinase
36
Increased enzyme synthesis can be ____ and release in serum correlates with degree of stimulation
induced
37
reflects the presence of inhibitors and activators
Enzyme Activity
38
Liver status marker
Alkaline phosphatase
39
Enzymes decreases in the presence of an inhibitor
Activity of serum
40
can be altered genetically
Enzyme activity
41
can alter its substrate affinity, co-factor binding stability, can be used as a diagnostic in comparison with normal enzyme
Mutation
42
identify specific messenger RNA or DNA sequences are replacing many traditional enzymatic based markers of genetic disease
PCR techniques
43
Measures levels of certain enzymes in blood or urine to assess how well the body’s systems are functioning
Enzyme test
44
Name some common enzymes used for clinical diagnosis.
Alanine aminotransferase (ALT), alkaline phosphatase, amylase, aspartate aminotransferase, creatine kinase, and lactate dehydrogenase.
45
Initial input of energy required for a chemical reaction to occur
Activation energy
46
Where the reaction is in between the reactant consumption and product formation
Transition state
47
____ systems are very sensitive to temperature changes
Biological
48
Enzyme controlled reactions proceed __ to ___ times faster than corresponding non-enzymic reactions
10^8 to 10^11
49
Catalyze one type of reaction for a single substrate
Absolute enzymes
50
for similar substrates
Group enzymes
51
for a specific type of bond
Linkage enzymes
52
States that the enzyme changes shape with the substrate, active site is not rigid.
Induced fit theory
53
Explains enzyme specificity and the loss of activity when enzymes denature
Lock and Key hypothesis
54
Suggests that the active site of an enzyme is flexible and adjusts its shape to fit the substrate
Induced fit model
55
Catalyzes the hydrolysis of peptide bonds
Chymotrypsin
56
reaction for the sucrase-catalyzed hydrolysis of sucrose
Sucrase + Sucrose → ES complex (reversible) → Sucrase + Glucose + Fructose (irreversible).
57
Defined as the moles of substrate converted to product per unit time
Enzyme activity
58
Steps of an enzymatic reaction
1. Substrate approaches the active site.
2. Enzyme-substrate complex forms.
3. Substrate is transformed into products.
4. Products are released.
5. Enzyme is recycled.
59
key points of the induced fit hypothesis
1. Some proteins can change their shape.
2. A substrate induces a change in the enzyme's conformation.
3. The active site is molded into a precise conformation
60
Test the absorbance
spectrophotometer
61
The rate of appearance of ___ or the rate of ____ of substrate.
product, disappearance
62
Factors affecting enzyme activity
1. Concentration of substrate
2. Concentration of enzyme
3. Temperature
4. pH
5. Activators
6. Inhibitors
63
proportional to the substrate concentration
increase in velocity
64
Faster reaction but it reaches a ____ point when all the enzyme molecules are occupied.
saturation
65
occurs when the enzyme is saturated
Maximum activity
66
Enzymes are most active at
optimum temperature
67
greatest number of collisions between enzyme and substrate.
optimum temperature
68
denatures the protein
Raise temperature
69
the increase in reaction rate with a 10 degrees Celsius rise in temperature.
Q10
70
pH optimum for pepsin and trypsin
Pepsin has an optimum pH of 3 in the stomach, while trypsin has an optimum pH of 8 in the small intestines.
71
optimum temperature for most enzymes outside the human body
30 degrees Celsius
72
typical pH range for most enzymes
6 to 8
73
Can lead to denaturation of an enzyme if the ionization state of amino acids critical to correct folding are altered
Extreme of pH
74
optimum pH for some enzymes in the body
7.4
75
Molecules that bind to enzymes and increase their activity.
Enzyme activators
76
Molecules called effectors (modifiers) that bind noncovalently at a site other than the active site.
Allosteric Binding Sites
77
addition or removal of phosphate groups to serine, threonine, or tyrosine residues
Covalent modification
78
Many enzymes are localized in specific organelles, which helps in the regulation of the metabolic pathway
Location within the cell
79
An inactive precursor of an enzyme that is activated by proteolysis.
Zymogen
80
cells can also regulate the number of enzymes present by altering the rate of enzyme synthesis.
Induction and repression
81
chemicals that reduce the rate of enzymic reactions, usually working at low concentrations and blocking the enzyme without destroying it
Inhibitors
82
is the substrate concentration at which the rate of the reaction is half-maximal, indicating the enzyme's affinity for the substrate
Michaelis constant
83
Can be assayed by the disappearance of substrate, appearance of product, continuous assay, and end point assay
Enzyme activity
84
an enzyme-catalyzed reaction is dependent upon the substrate concentration
velocity (V)
85
At the start of the reaction, it is first order with respect to substrate concentration, and at the end, it is zero order with respect to substrate concentration.
order of reaction change
86
describes the kinetic behavior of many enzymes, relating reaction rate to substrate concentration
Michaelis-Menten equation
87
The rate of reaction is ____ on substrate concentration.
dependent
88
Kinetics of simple enzyme-catalyzed reactions
Saturation Kinetics
89
are based on data from batch reactors with constant liquid volume where initial substrate and enzyme concentrations are known
Langmuir-Hinshelwood Kinetics
90
are often just above the substrate concentration in a cell, and rates of reaction are sensitive to small changes in cellular substrate concentrations
Km values
91
can be obtained from simple reaction scheme that involves a reversible step for enzyme-substrate complex formation and a dissociation step from the ES complex.
Saturation kinetics
92
The maximum forward velocity of the reaction changes if more enzyme is added, but the addition of more substrate has no influence on it
rapid-equilibrium approach
93
is used to determine rate parameters for Michaelis-Menten kinetics
Lineweaver-Burk
94
represents the relationship between substrate concentration [S] and the rate of reaction v, allowing for the determination of Km and Vmax
Hanes - Woolf Plot
95
Enzyme lose its catalytic activity due to the alteration of its three-dimensional shape
denatured
96
during purification can occur due to pH extremes or temperature changes
Enzyme denaturation
97
The binding of one substrate to the enzyme facilitates binding of other substrate molecules
Allosteric enzymes
98
certain compounds may bind to enzymes and reduce their activity
Inhibited enzyme kinetics
99
form a stable complex with the enzyme and reduce enzyme activity
Irreversible inhibitors
100
may dissociate more easily from the enzyme after binding
Reversible inhibitors
101
are usually substrate analogs and compete with the substrate for the active site of the enzyme
Competitive inhibitors
102
are not substrate analogs; they bind on sites other than the active site and reduce enzyme affinity to substrate
Noncompetitive inhibitors
103
bind to the ES complex only and have no affinity for the enzyme itself
Uncompetitive inhibitors
104
can be overcome by high concentrations of substrate.
Competitive inhibition
105
an increased value of the denominator without substrate concentration, leading to a reduced reaction rate
net effect of competitive inhibition
106
high substrate concentrations may cause inhibition in some enzymatic reactions.
Substrate inhibition
107
_____ of the pH optimum of enzymes requires a knowledge of the active site characteristics of enzymes, which are very difficult to obtain.
Theoretical prediction
108
may affect the maximum reaction rate, the constant, and the stability of the enzyme
Changes in pH
