Enzymology Flashcards
(150 cards)
1
Q
What are enzymes?
A
These are proteins that catalyze chemical reactions
2
Q
Identify the three main characteristics of enzymes.
A
They do not alter the equilibrium of a reaction
They are not consumed or altered
They’re highly specific for each reaction
3
Q
What is enzyme classification based on?
A
Typically based on the type of reaction they catalyze
4
Q
What are oxidoreductases?
A
These are enzymes that catalyze oxidation/reduction reactions
5
Q
What are transferases?
A
These are enzymes that transfer groups other than hydrogens like amines
6
Q
What are hydrolases?
A
These are enzymes that catalyze the hydrolysis of an ether or ester.
7
Q
List some classes or enzymes.
A
Hydrolases Transferases Oxidoreductases Lyases Isomerases Ligases
8
Q
What type of compound are enzymes?
A
Proteins
9
Q
How are enzymes structured?
A
They have primary, secondary, tertiary and quaternary structures
10
Q
What shale do enzymes have?
A
Enzymes are roughly globular in shape
11
Q
What does denaturation imply for enzymes?
A
Denaturation in enzymes means a change in their structure which causes loss of activity
12
Q
What is the primary structure of an enzyme?
A
Chain of specific amino acid sequences
13
Q
What is the secondary structure of an enzyme?
A
Alpha helix and beta pleated sheet
14
Q
What is the tertiary structure of an enzyme?
A
Comprehensive 3-D structure
15
Q
What is the quaternary structure of an enzyme?
A
Multiple subunits of AA chains joining together
16
Q
What are the two enzyme sites?
A
The active site and the allosteric site
17
Q
What is the active site of an enzyme?
A
The active site is a specific AA sequence that binds a specific substrate
18
Q
On what site of an enzyme does a substrate bind to?
A
Active site
19
Q
By what enzyme structure is the active site formed?
A
Tertiary structure
20
Q
Are the bonds binding a substrate to an active site covalent?
A
No
21
Q
What type of bond is there between an active site and a substrate?
A
Hydrogen or Van def Waals forces
22
Q
This site is where bonds of the substrate are broken and new bonds are formed resulting in a new product .
A
The active site
23
Q
What happens when a specific substrate binds to a specific amino acid sequence of an enzyme?
A
Bonds of that substrate are broken and new bonds are formed resulting in a new product
24
Q
What does a change to active site cause?
A
Any change to the active site of an enzyme affects substrate affinity to enzyme.
25
What is the allosteric site of an enzyme?
This is an area in the enzyme that affects enzyme activity by allowing molecules to either activate or inhibit an activity
26
What are the two types of allosteric sites?
Allosteric activators and allosteric inhibitors
27
What does an allosteric activator do?
It enhances the substrate-enzyme binding and make their interaction more efficient
28
What does an allosteric inhibitor do?
It changes the conformation of the active site, preventing the substrate from binding, thus the reaction can’t occur
29
What do you understand by isoenzymes?
These are multiple forms of an enzyme with different amino acid sequences but that catalyze the same biochemical reaction
30
What are the properties of isoenzymes?
They have different molecular structures
They have different genetic origins
Catalyze the same biochemical reaction
31
What do you understand by cofactors?
These are non protein substances necessary for enzyme activity to occur.
32
These non protein substances are sometimes needed for an enzyme to be catalytically active.
Cofactors
33
How do cofactors help enzyme activity?
By helping the enzyme attract the substrate
34
When cofactors are organic, how are they called? Give examples.
Coenzymes. NAD, vitamin B6
35
When cofactors are inorganic, how are they called?
Activators
36
What are prosthetic groups?
Prosthetic groups are cofactors that are bound tightly to enzymes through covalent bonds
37
How is an enzyme that normally has a cofactor but is not currently bound to it called?
Apoenzyme
38
How is the entire structure if an enzyme bound to its cofactors called?
Holoenzyme
39
What is international unit?
This is the amount of enzyme that will catalyze the reaction of one micro molecule of substrate per minute under specific conditions.
40
What are enzymes quantified relative to?
To their activity and not their direct concentration
41
What is katal measurement?
This is an SI measurement defined as the number of moles of substrate converted to product in one second.
42
What is enzyme kinetics?
This is the relationship between enzyme, substrate and product. That is, how quickly the enzyme works on substrate to form product.
43
Catalytic mechanism is stated as?
E + S -> ES -> P + E
44
List the influencers of enzymatic reactions.
```
Enzyme concentration
Substrate concentration
pH
Temperature
Cofactor concentration
Inhibitors
```
45
How does enzyme concentration affect enzymatic reactions?
The overall rate of enzymatic reaction is proportional to the concentration of enzyme present in the system with constant substrate
46
How does substrate concentration affect enzymatic reaction?
Reaction rate is proportional to substrate concentration if enzyme concentration is kept constant
47
What is first order kinetics as per substrate concentration?
First order kinetics happens when substrate concentration is low. The reaction rate is proportional to substrate concentration as long as there is plenty of enzyme
48
This kinetics takes over when substrate concentration is high. The reaction rate is independent of the substrate concentration because all enzyme is bound and the reaction’s max velocity is achieved.
Zero order kinetics
49
What is the M-M equation?
This is the substrate rate curve that expresses the relationship between substrate concentration and the velocity of the enzymatic .
50
The M-M equation is expressed as what formula?
V = Vmax(S) / Km+S
51
What is Vmax per the M-M curve?
Reaction velocity at maximal substrate concentration
52
What us Km per M-M curve?
M-M constant for a given substrate acting on a given enzyme . Concentration at which half of the maximum velocity is reached
53
What is the Lineweaver burk plot?
It’s a plot that expresses M-M kinetics as a straight line by using reciprocal numbers
54
What is Vmax with Lineweaver-Burk plot?
Vmax is the reciprocal of the y-intercept of the straight line
55
What is Km with Lineweaver-Burk plot?
Km is the negative reciprocal of the x-intercept of the straight line
56
How does pH affect enzymatic reactions?
Reaction rates drop when pH decreases because of the effects of hydrogen ions on active site
57
How does temperature affect enzymatic reactions?
Too high temperatures denature enzymes and reaction rate will drop
58
How does cofactor concentration affect enzymatic reactions?
Increased cofactors concentration increases the velocity of the reaction by the formation of the most active state of the enzyme,
59
What are inhibitors?
Substances that reversibly inhibit normal e Ahmed reactions
60
How do competitive inhibitors function?
They bind the active site and interrupt substrate binding to the active site. Increase Km and traduce substrate affinity to active site while Vmax remains unchanged
61
How do noncompetitive inhibitors function?
They bind to a site other than the active site like the allosteric site, decreasing Vmax and decreasing enzyme activity while Km era aims unchanged
62
How do uncompetitive inhibitors function?
They bind to the ES complex essentially keeping it from forming a product. Both Km and Vmax are changed
63
What supplies the source if most enzymes?
Most enzymes are synthesized
64
Do enzymes function intracellularly or extracellularly?
Intracellularly
65
What will be the cause of increased plasma/serum levels of enzymes?
Cell damage that made enzymes leak into blood
66
Name some enzymes that are secreted and active in extracellular fluid.
Amylase
Lipase
Acid phosphate
Coag enzymes
67
I’d study the factors affecting blood levels of enzymes
Leakage of enzyme from cells
Clearance of enzymes
Altered enzyme production
68
Where does clearance of enzymes normally occur?
In the spleen and liver
69
Why are changes in enzymatic activity not definitively diagnostic?
Because there is no completely organ specific enzyme
70
What type of enzyme is creatine kinase?
A muscle enzyme
71
List some muscle enzymes.
Creatine kinase CK
Lactate dehydrogenase LDH
Aldolase ALD
72
What is Creatine kinase?
A transferase that reversibly moves phosphate groups
73
What does CK require for activation?
Mg
74
What reaction dies CK catalyze?
The reaction that firms ATP in tissues, especially contractile systems
75
In what muscles is CK found?
Skeletal muscle
Brain muscle
Cardiac muscle
Others
76
What structure is CK?
CK in a dimer
77
How many isoenzymes does CK have?
3
78
List the isoenzymes of CK
CK B-B
CK B-M
CK M-M
79
Where is CK B-B located?
Mostly in the brain. Also prostate, GI and genitourinary tracts
80
What percentage of total CK is CK B-B?
1%
81
What is the most increased CK isomer in acute myocardial infarction?
CK M-B
82
Where is CK M-B located?
Cardiac muscle. Some skeletal
83
What percentage of total CK is CK M-B?
<5%
84
Where is CK M-M located?
Most.yes skeletal muscle and some cardiac
85
What percentage of total CK is CK M-M?
~94%
86
Why is CK normal in acute hepatitis or anemia?
Liver and RBCs and almost zero CK activity
87
In what conditions are CK levels elevated?
Injury, inflammation, necrosis of heart or skeletal muscle
Diseases of skeletal muscle like muscular dystrophy , muscular crush injuries, extraneous physical activity
Diseases of heart muscle like MI, cardiac trauma like surgery
88
What is LDH?
Lactose dehydrogenase is an oxidoreductase. A hydrogen transfer enzyme that utilizes NAD as coenzyme.
89
What reaction does LDH catalyze?
The interconversion of lactate and pyruvate
90
Where is LDH found?
Heart muscle, liver, RBCs, skeletal, kidneys
91
In what conditions are LDH levels high?
Pernicious anemia
Crush injuries
Liver disease
Heater attack
92
What is aldolase?
This is a lyase found in high amount in striated muscle and liver tissue.
93
What type of reaction does aldolase catalyze?
Important reactions in the glycolytic breakdown of glucose to pyruvate/lactate for energy
94
What are the specimen requirements for muscle enzymes?
Heparinized plasma or serum
| No hemolysis
95
What are the major sources of amylase?
Pancreas and salivary glands
96
What are the two isoenzymes of amylase?
P-amylase and S-amylase
97
What is amylase?
This is a hydrolase that catalyzes the hydrolysis of starches and glycogen to produce simple sugars.
98
Why is amylase present in urine?
It is small and can pass through the glomeruli
99
In what conditions are Amylase levels high?
Acute pancreatitis
Salivary gland lesions
Some drug usage
100
Amylase levels rise how many hours after onset of symptoms? When does it peak?
2-12 hours after onset of symptoms. Peaks at~24 hours
101
What amylase levels remain high for longer between serum and urine?
Urine
102
What is lipase?
Lipase is a hydrolase enzyme that catalyzes the hydrolysis of glycerol esters to form fatty acids, especially triglycerides
103
Where is lipase found in the body?
In the acinar cells of the pancreas with small amounts in stomach and intestine
104
Lipase is examines exclusively to diagnose what condition?
Acute pancreatitis
105
Lipase levels rise how many hours after acute pancreatitis attach onset? When does it return to normal?
4-8hours and returns to normal 8-14 days later
106
What enzyme is considered the most specific marker of acute pancreatitis?
Lipase
107
What type of specimen is required for amylase and lipase studies?
Serum or heparinized plasma with no hemolysis or lipemia
108
What other two specimens can be used to test amylase but not lipase?
Urine and saliva
109
What type of enzyme is lactate dehydrogenase?
Oxidoreductase
110
Where is lactate dehydrogenase found in the body?
```
Heart muscle
Liver
Rbcs
Skeletal muscle
Kidneys
```
111
Lists where the different lactate dehydrogenase isoenzymes are located?
```
LD1 RBCs and heart
LD2 RBCs, heart and WBCs
LD3 Lungs
LD4 kidneys, pancreas, placenta
LD5 Liver, skeletal muscle
```
112
Why is lactate dehydrogenase measurement common in hematology and oncology?
Because lactate dehydrogenase is elevated in megaloblastic anemia and some cancers
113
What are cholinesterases?
A group of hydrolases that hydrolyze the esters of choline
114
Why is cholinesterase important?
It is important to breakdown neurotransmitter in order to relax a nerve signal after it is triggered so that it doesn’t remain locked in place
115
This is enzyme is important in breaking down neurotransmitter in order to relax a nerve signal after it is triggered so that it doesn’t remain locked in place
Cholinesterase
116
What are the two types of cholinesterase?
```
Acetylcholinesterase (true cholinesterase)
Acylcholine acylhydrolase (pseudocholinesterase)
```
117
Which one of the two types of cholinesterase is considered most clinically significant?
Acylcholine acylhydrolase
118
AChe is found in
Brain cells, RBCs, nerve cells
119
CHE is found in
Liver, pancreas, heart, serum
120
CHE is decreased in what conditions?
Liver disease
Insecticide poisoning
Genetics
121
Where is G6PD located in the body?
Adrenal glands, spleen, thymus, RBCs and lymph nodes
122
What is G6PD?
It’s an oxidoreductase that catalyzes the oxidation of G6P to form 6-phosphoglucuronate
123
Why is NADPH production important during oxidation of G6P?
To maintain glutathione (GSH) level in RBC
124
What is GSH?
It is a major antioxidant in RBCs which protects RBCs from being attacked by reactive oxygen species without which RBCS will be subject to oxidative damage and hemolysis
125
Deficiency in G6PD results in what?
Hemolytic anemia
126
What is ACP used for?
To assess bone issues
127
This enzyme is a marker for bone resorption
Acid phosphatase
128
What is the heart?
This is a four chambered muscular organ with two sides for pumping
129
What is the pumping action of the heart responsible for?
Circulation of blood through arteries and veins
130
What quantity of blood does the heart pump!
6L of blood per minutes or ~85mL per beat
131
What is another name for the atria?
Hallway
132
What is another name for the ventricles?
Cavity of little belly
133
What moves into the right atrium from the body?
Deoxygenated blood
134
What happens with the left atrium?
Oxygenated blood moves into the left atrium from pulmonary veins of lungs
135
What does the right ventricle do?
Pumps deoxygenated blood into the lungs
136
What does the left ventricle do?
Pumps oxygenated blood into the aorta and subsequent large arteries of the head, trunk and extremities
137
Which ventricle is considered the strongest one?
The left ventricle
138
What divides the atria?
Interatrial septum
139
What is the use of valves?
Prevent the back flow of blood through the heart
140
What separates the ventricles?
Intraventricular septum
141
What are coronary arteries?
These are vessels on the surfaces of the heart that supply blood to the cardiac muscle
142
Why does cardiac muscle require a constant blood supply?
Due to strict oxygen requirements
143
What happens if coronary arteries are blocked?
There’s loss of blood/oxygen (ischemia) to muscle which produces tissue death, muscle cells leak out enzymes and proteins, heartbeat could go arrhythmic
144
What are the symptoms of cardiac ischemia?
Chest pain
Arrhythmia
Heart failure/MI
145
What is heart failure / MI?
This is when the heart does not pump enough blood to meet the O2 needs of peripheral tissue
146
What are some cardiac diseases that can cause heart failure?
CHF
CAD; ACS
Cardiomyopathy
147
This is myocardial ischemia resulting for an acute/sudden reduced blood flow event leading to either incomplete or complete blockage of a Cora ray artery
Coronary artery disease
148
What is the difference between angina and AMI?
Angina is incomplete, reversible, no tissue necrosis while AMI is complete, irreversible with tissue necrosis and has to be confirmed with cardiac markers and mostly EKG
149
What arev5he two types of AMI?
NSTEMI
| STEMI
150
What is angina pectoris?
Deficiency of oxygen to cardiac muscle from incomplete obstruction of coronary arteries
