ENZYMOLOGY Flashcards
1
Q
What is a coenzyme?
A
Organic molecules
2
Q
A coenzyme or metal ion that is very tightly or even covalently bound to the enzyme is called?
A
Prosthetic group
3
Q
complete catalytically active enzyme together with its bound coenzyme is called
A
Holoenzyme
4
Q
The protein part of holoenzyme is called?
A
Apoenzyme
5
Q
Which suffix is added to the name of the substrate or to a word or to a phrase describing the activity of enzyme, to name an enzyme?
A
-Ase
6
Q
Which enzyme transfers phosphate groups?
A
Hexokinase
7
Q
The site where enzyme catalyzed reaction takes place is called?
A
Active Site
8
Q
The molecule that is bound and acted upon by the enzyme is called?
A
Substrate
9
Q
Who proposed the existence of proteolytic enzymes as proteins?
A
Northrop
10
Q
What will happen to the enzyme-catalyzed reaction if temperature is increased?
A
Rate of reaction increases
11
Q
What will happen to reaction if more enzymes are added?
A
Rate of reaction increase
12
Q
How metal ions participate in catalysis?
A
By causing reduction and oxidation reactions between enzyme and substrate
By causing ionic interactions between enzyme and substrate
13
Q
What is Vmax
A
Maximum rate of reaction
14
Q
What is Km in Michaelis-Menten Equation?
A
Michaelis-Menten constant
15
Q
Which enzymes are said to follow Michaelis-Menten kinetics?
a. Enzymes which show parabolic dependence of rate of reaction and substrate
b. Enzymes which show circular dependence of rate of reaction and substrate
c. Enzymes which show hyperbolic dependence of rate of reaction and substrate
d. None of the above
A
Enzymes which show hyperbolic dependence of rate of reaction and substrate
16
Q
Double-reciprocal plot is also called?
A
Line plot
17
Q
Which scientist proposed lock and key model in 1894?
A
Emil Fisher
18
Q
What is induced fit?
a. when enzyme change shape due to absence of substrate
b. when enzyme do not change shape due to absence of substrate
c. when enzyme change shape due to presence of substrate
d. when enzyme do not change shape due to presence of substrate
A
when enzyme change shape due to presence of substrate
19
Q
Who postulated induced fit in year1958?
A
Daniel Koshland
20
Q
A purely competitive enzyme inhibitor has which of the following kinetic effects?
A
increases Km without affecting Vmax
21
Q
Enzymes as classic catalysts accomplish which of the following energy effects?
A
lower the energy of activation
22
Q
Synthesis of an enzyme promoted by the substrate on which it acts, is characterized by the term
A
Induction
23
Q
Which statement about the active site is incorrect?
A. It is composed of linearly arranged amino acid chain.
B. It is relatively small compared to the total bulk of the enzyme.
C. It does not generally form covalent interaction with substrates.
D. It is three-dimensional in quality.
E. none of these
A
It is composed of linearly arranged amino acid chain.
24
Q
Which statement about most enzymes is incorrect?
A. They increase the rapidity of the reactions they catalyze.
B. They are specific for the substrate as well as the reaction catalyzed.
C. They are large polypeptides with high molecular weight.
D. They are most active near neutral pH.
E. They are not affected by changes in temperature.
A
They are not affected by changes in temperature.
25
Michaelis & Menten did not make which of the following assumptions concerning analyses of enzyme action?
A. The initial reaction of velocity should be measured since most of the substrate has not been converted to product.
B. Maximal velocity is reached when the concentration of ES complex is equal to the total number of enzymes.
C. The formation of the ES complex does not appreciably decrease the [S].
D. For analysis of enzyme kinetics, the total [E] studied at each [S] is fixed.
E. Plotting the reciprocal of [V] and [S] will produce an ideal linear curve.
E. Plotting the reciprocal of [V] and [S] will produce an ideal linear curve.
26
Which enzymes are used to diagnose liver diseases?
AST AND ALT
27
Which enzyme cannot be used to detect acute myocardial infarction (AMI)?
A. ACP
B. CK
C. AST
D. LDH
ACP
28
Which of the following enzyme pairs cannot be used in the diagnosis of liver disorders?
A. ALP & LAP
B. GGT & 5’-NT
C. LDH & AST
D. ACP & ALS
ACP AND ALS
29
which pair has clinical utility for AMI detection?
A. ALP & LAP
B. GGT & 5’-NT
C. LDH & AST
D. ACP & ALS
LDH AND AST
30
Which fraction is expected to be elevated in alcoholic cirrhosis of the liver?
GGT
31
Aspartate aminotransferase (AST) and alanine aminotransferase the following disease?
Viral hepatitis
32
Which two physiologic conditions can greatly elevate blood alkaline phosphatase?
growth, third trimester of pregnancy
33
A physician suspects his patient has pancreatitis. Which test(s) would be most indicative of this disease?
Amylase
34
Which of the following chemical determinations may be of help in establishing the presence of seminal fluid?
Acid phosphatase
35
The most sensitive enzymatic indicator for liver damage from ethanol intake is
Gamma-glutamyl transferase (GGT
36
. A serum sample drawn in the emergency room from a 42-year-old man yielded the following laboratory results:
CK 385 Units (Normal = 15-160)
AST 73 Units (Normal = 0-48)
CK-MB 106 Units (Normal = 2-12)
Myocardial Infarction
37
In competitive inhibition of an enzyme reaction the
A. Inhibitor binds to the enzyme at the same site as the substrate
B. Inhibitor often has a chemical structure different from that of the substrate
C. Activity of the reaction can be decreased by increasing the concentration of the substrate
D. Activity of the reaction can be increased by decreasing the temperature
Inhibitor binds to the enzyme at the same site as the substrate
38
The presence increased CK-MB activity on a CK electrophoresis pattern is most likely found in a patient suffering from
Myocardial Infarction
39
Which of the following enzymes catalyzes the conversion of starch to glucose and maltose?
Amylase
40
Which of the following enzymes are used in the diagnosis of acute pancreatitis?
Amylase and trypsin
41
The specific activity of an enzyme would be reported in which of the following units of measure:
Units of activity per milligram of protein
42
The Km value & Vmax in competitive inhibition are
A. increased and decreased respectively.
B. decreased and increased respectively.
C. increased and unchanged respectively.
D. unchanged and decreased respectively.
E. both decreased
increased and unchanged respectively.
43
The Km value & Vmax in noncompetitive inhibition are
unchanged and decreased respectively.
44
The Km value & Vmax in uncompetitive inhibition are
both decreased.
45
The functions of many enzymes, membrane transporters, and other proteins can be quickly activated or deactivated by phosphorylation of specific amino acid residues catalyzes by enzymes called:
Kinases
46
The chemotherapy drug fluorouracil undergoes a series of chemical changes in vivo that results in a covalent complex such that it is bound to both thymidylate synthase and methylene-tetrahydrofolate. The inhibition of deoxythymidilate formation and subsequent blockage of cell division is due to which of the following:
Irreversible inhibition
47
The Lineweaver-Burk plot is used to graphically determine Km and Vmax for an enzyme that obeys classic Michaelis-Menten Kinetics. When V is the reaction velocity at substrate concentration S, the Y axis experimental data in the Lineweaver- Burk plot are expressed as:
1/V
48
In the Lineweaver-Burk plot, the Vmax of an enzyme is:
a. Reciprocal of the absolute value of the intercept of the curve with the x axis
b. Reciprocal of the absolute value of the intercept of the curve with the y axis
c. Absolute value of the intercept of the curve with the x axis
d. Slope of the curve
e. Point of inflection of the curve
Reciprocal of the absolute value of the intercept of the curve with the y axis
49
noncompetitive inhibitor of an enzyme does which of the following:
Decreases Vmax
50
Digestive enzymes such a pepsin, trypsin, and chymotrypsin are synthesized as inactive precursors. The preproteins of the active enzymes are termed :
Zymogens
51
Competitive inhibitors typically resemble the:
Substrate(s)
52
enzymes used to detect hepatobiliary diseases:
a. GGT
b.ALT
c.ALP
d.ALS
e.LAP
GGT
ALP
LAP
53
choose enzymes used to detect hepatic parenchymal disorders.
a. SDH
b.LDH
c.CPK
d.AMS
e.ALT
SDH
LDH
ALT
54
corresponds to the diagnostic enzymes for acute myocardial infarction:
a. CK-MB
b. ALT
c. Troponin T
d. AST
e. HBD
CK-MD
AST
HBD
55
corresponds to the diagnostic enzymes for prostatic cancer:
PSA
ACP
56
Which enzyme is used to detect insecticide poisoning?
Acetylcholinesterase
57
The graph that plots substrate concentration versus reaction rate is called
Michaelis-Menten plot
58
Which of the following is not the property of enzyme:
a.to be converted in the course of reaction
b. specificity towards a substrate or a group of substrates
c. alters the rate of reaction a thousand or a million-fold
d. protein with which a substrate can attach reversibly
to be converted in the course of reaction
59
On which organism or sample was the term enzyme literally associated?
Yeast
60
In early 19the century, which scientist studied fermentation of sugar to alcohol using a cell-free extract?
Edward Buchner
61
What was the name given to enzymes by Louis Pasteur that he based from a process he himself discovered?
Ferment
62
In which year Edward Buchner discovered that yeast extract can cause the fermentation of sugar to alcohol?
1907
63
Who gave the word “enzymes” to catalytic molecules?
Kuhne
64
In which year James Sumner isolated and crystallized urease?
1926
65
All enzymes are made up of which biomolecules (or, biomolecules)?
Proteins
RNA
66
What is an inorganic cofactor?
Metal ions
67
What is a coenzyme?
Organic molecules containing metals
Organic molecules
68
Enzymes that differ in structure and origin but same reaction catalyzed are called:
Isoenzyme
69
A complete catalytically active enzyme together with its bound enzyme or metal ions is called?
Complex enzyme
70
The nonprotein part of holoenzyme is called?
Apoenzyme
71
Which suffix is added to the name of the substrate or to a word or to a phrase describing inactivity?
-ogen
72
In how many classes enzyme is divided by the IUBMB Enzyme Commission?
6
73
The site where enzyme catalyzed reaction takes place is called?
Active site
74
The molecule that is bound and acted upon by the enzyme but suppresses its function is termed:
Inactivator
75
The action of a biocatalyst affects:
Rate of reaction
76
What will happen to reaction if temperature is increased
Rate of reaction increase
77
What will happen to reaction if enzyme is added
Rate of reaction increase
78
The enzyme that does not require a carbohydrate substrate is:
Catalase
79
The step which decides the rate of reaction is called?
Rate limiting step
80
The step which decides the rate of reaction is called?
Rate of limiting step
81
How metal ions participate in catalysis?
a. By causing reduction and oxidation reactions between enzyme and substrate
b. By causing ionic interactions between enzyme and substrate
82
What are the most common point group for protease enzymes?
Serine
83
The enzyme chymotrypsin has this number of point groups in its active site:
3
84
What is enzyme kinetics?
a. Studying the mechanism of rate of reaction of enzyme
b. Looking into the factors affecting enzyme activity
c. Both a and b
85
What is Vmax?
Maximum rate of reaction
86
Who gave the general theory of enzyme action and saturable plot between [S] and V in 1913?
Leonor Michaelis and Maud Menten
87
In an enzyme catalyzed reaction, enzyme exists in which form?
Free form
Combined form
ES form
88
What does Km stand for in Michaelis-Menten equation?
Michaelis-Menten constant
89
Which enzymes are said to follow Michaelis-Menten kinetics?
Enzymes which show hyperbolic dependence of rate of reaction and substrate
90
Double-reciprocal plot is also called?
Lineweaver-Burk plot
91
What is k1?
The rate constant of the enzyme-substrate complex formation
92
What is the relationship between Km and enzyme affinity for substrate?
Inversely proportional
93
A purely competitive enzyme inhibitor has which of the following kinetic effects?
increases Km without affecting Vmax
94
Which statement about the active site is incorrect?
A. It is composed of linearly arranged amino acid chain.
B. It is relatively small compared to the total bulk of the enzyme.
C. It does not generally form covalent interaction with substrates.
D. It is three-dimensional in quality.
E. none of these
It is composed of linearly arranged amino acid chain.
95
Which statement about most enzymes is incorrect?
A. They increase the rapidity of the reactions they catalyze.
B. They are specific for the substrate as well as the reaction catalyzed.
C. They are large polypeptides with high molecular weight.
D. They are most active near neutral pH.
E. They are not affected by changes in temperature.
They are not affected by changes in temperature.
96
The official name of an enzyme is accompanied by an EC followed by 4 numbers separated by dots. What does EC stand for?
Enzyme commision
97
Which anticoagulant cannot be used for plasma collection for enzyme assays because it is regarded as an enzyme poison?
Flouride
98
In enzyme analysis of serum substances, buffers actually
act as a carrier for ions
99
A physician suspects his patient has acute hepatitis. Which test would be least indicative?
Amylase
100
In competitive inhibition of an enzyme reaction the
Inhibitor binds to the enzyme at the same site as the substrate
101
Which of the following enzymes catalyzes the conversion of starch to glucose and maltose?
Amylase (AMS)
102
The specific activity of an enzyme would be reported in which of the following units of measure:
Units of activity per milligram of protein
103
The inactive form of an enzyme is called the
Proenzyme
104
Aminotransferase enzymes (AST and ALT) catalyze the
Exchange of amino and keto groups between alpha-amino and alpha-keto acids
105
T he apoenzyme-coenzyme complex is also regarded as
holoenzyme
106
Enzyme activity can be measured via the following EXCEPT A. decrease in substrate concentration
B. extent of utilization of coenzyme
C. appearance of products due to catalysis
D. increase in temperature due to catalysis
D. increase in temperature due to catalysis
107
Biologic catalysts are characterized by all of the following EXCEPT
A. can either be organic or inorganic
B. decrease the energy of activation
C. not consumed or altered in the reaction
D. relatively high stereospecificity
A
108
Which of the following are surely derived from vitamin?
Coenzymes
109
The site where catalysis and conformational changes occur in an enzyme is the
Active site
110
The amount of enzyme that will convert 1 mole of substrate converted per second per liter of sample:
Katal unit
111
The amount of enzyme that will convert 1 micromole of substrate converted per minute per liter of sample:
IU/L
112
The prostatic ACP is characterized by the following, except:
A. It is tartrate-stable
B. It is not affected by Cu++ ions
C. It is formol-stable
D. It is associated with prostatic cancer
C
113
Select the polypeptide chain combination designated LD 5.
M4
114
A physician suspects his patient has pancreatitis. Which test(s) would be most indicative of this disease?
Amylase
115
One international unit of enzyme activity is the amount of enzyme that, under specified reaction conditions of substrate concentration, pH, and temperature, causes utilization of substrate at the rate of:
1 micromole/min
116
Which of the following chemical determinations may be of help in establishing the presence of seminal fluid?
Acid phosphatase
117
Increased total lactic dehydrogenase (LD) activity, confirmed to fraction 4 and 5 , is most likely to be associated with:
Acute viral hepatitis
118
Regan isoenzyme has the same properties as alkaline phosphatase that originates in the :
Placenta
119
Given the following results:
Alkaline phosphatase (markedly increase)
Alanine aminotransferase (slight increase)
Aspartate aminotransferase (slight increase)
Gamma-glutamyl transferase (marked increase)
This is most consistent with:
Chronic hepatits
120
Given the following results:
Alkaline phosphatase (slight increase)
Alanine aminotransferase (marked increase)
Aspartate aminotransferase (marked increase)
Gamma-glutamyl transferase (slight increase)
This is most consistent with:
Acute parenchymal liver disease
121
The presence increased CK-MB activity on a CK electrophoresis pattern is most likely found in a patient suffering from:
Myocardial infarction
122
129. A serum sample drawn in the emergency room from a 42-year-old man yielded the following laboratory results:
CK 185 Units (Normal = 15-160)
AST 123 Units (Normal = 0-48)
CK-MB 6 Units (Normal = 2-12)
Which of the following conditions might account for these values?
Crush injury to the thigh
123
When myocardial infarction occurs, the first enzyme to become elevated is:
Ck
124
In the determination of lactate dehydrogenase at 340nm, using pyruvate as the substrate, one actually measures the:
Decrease in NADH
125
Which of the following enzymes catalyzes the conversion of starch to glucose and maltose?
Amylase
126
A scanning of a CK isoenzyme fractionation revealed two peaks: a slow cathodic peak (CK-MM) and an intermediate peak (CK-MB). A possible interpretation for this pattern is:
Myocardial infarction
127
Which of the following enzymes are used in the diagnosis of acute pancreatitis?
Amylase and lipase
128
Which of the following is a glycolytic enzyme that catalyzes the cleavage of fructose-1, 6-diphosphate to glyceraldehyde-3-phosphate and dihydroxyacetone phosphate?
Aldolasw
129
The greatest activities of serum AST and ALT are seen in:
Metastatic hepatic carcinoma
130
An electrophoretic separation of lactate dehydrogenase isoenzymes that demonstrates an elevation in LD- 1 and LD-2 in a “flipped” pattern is consistent with:
Myocardial infarction
131
Which of the following is a characteristic shared by lactate dehydrogenase, malate dehydrogenase, isocitrate dehydrogenase and hydroxybutyrate dehydrogenase?
They are class III enzymes.
132
The most heat labile fraction of alkaline phosphatase is obtained from:
Bone
133
The aldehyde transport coenzyme is derived from:
Thiamine
