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Clinical Chem II > Enzymology > Flashcards

Enzymology Flashcards

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1
Q

What are enzymes?

A

These are proteins that catalyze chemical reactions

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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

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3
Q

What is enzyme classification based on?

A

Typically based on the type of reaction they catalyze

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4
Q

What are oxidoreductases?

A

These are enzymes that catalyze oxidation/reduction reactions

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5
Q

What are transferases?

A

These are enzymes that transfer groups other than hydrogens like amines

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6
Q

What are hydrolases?

A

These are enzymes that catalyze the hydrolysis of an ether or ester.

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7
Q

List some classes or enzymes.

A 
Hydrolases
Transferases 
Oxidoreductases 
Lyases 
Isomerases 
Ligases
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8
Q

What type of compound are enzymes?

A

Proteins

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9
Q

How are enzymes structured?

A

They have primary, secondary, tertiary and quaternary structures

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10
Q

What shale do enzymes have?

A

Enzymes are roughly globular in shape

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11
Q

What does denaturation imply for enzymes?

A

Denaturation in enzymes means a change in their structure which causes loss of activity

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12
Q

What is the primary structure of an enzyme?

A

Chain of specific amino acid sequences

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13
Q

What is the secondary structure of an enzyme?

A

Alpha helix and beta pleated sheet

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14
Q

What is the tertiary structure of an enzyme?

A

Comprehensive 3-D structure

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15
Q

What is the quaternary structure of an enzyme?

A

Multiple subunits of AA chains joining together

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16
Q

What are the two enzyme sites?

A

The active site and the allosteric site

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17
Q

What is the active site of an enzyme?

A

The active site is a specific AA sequence that binds a specific substrate

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18
Q

On what site of an enzyme does a substrate bind to?

A

Active site

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19
Q

By what enzyme structure is the active site formed?

A

Tertiary structure

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20
Q

Are the bonds binding a substrate to an active site covalent?

A

No

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21
Q

What type of bond is there between an active site and a substrate?

A

Hydrogen or Van def Waals forces

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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

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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

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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.

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25
Q

What is the allosteric site of an enzyme?

A

This is an area in the enzyme that affects enzyme activity by allowing molecules to either activate or inhibit an activity

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26
Q

What are the two types of allosteric sites?

A

Allosteric activators and allosteric inhibitors

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27
Q

What does an allosteric activator do?

A

It enhances the substrate-enzyme binding and make their interaction more efficient

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28
Q

What does an allosteric inhibitor do?

A

It changes the conformation of the active site, preventing the substrate from binding, thus the reaction can’t occur

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29
Q

What do you understand by isoenzymes?

A

These are multiple forms of an enzyme with different amino acid sequences but that catalyze the same biochemical reaction

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30
Q

What are the properties of isoenzymes?

A

They have different molecular structures
They have different genetic origins
Catalyze the same biochemical reaction

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31
Q

What do you understand by cofactors?

A

These are non protein substances necessary for enzyme activity to occur.

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32
Q

These non protein substances are sometimes needed for an enzyme to be catalytically active.

A

Cofactors

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33
Q

How do cofactors help enzyme activity?

A

By helping the enzyme attract the substrate

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34
Q

When cofactors are organic, how are they called? Give examples.

A

Coenzymes. NAD, vitamin B6

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35
Q

When cofactors are inorganic, how are they called?

A

Activators

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36
Q

What are prosthetic groups?

A

Prosthetic groups are cofactors that are bound tightly to enzymes through covalent bonds

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37
Q

How is an enzyme that normally has a cofactor but is not currently bound to it called?

A

Apoenzyme

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38
Q

How is the entire structure if an enzyme bound to its cofactors called?

A

Holoenzyme

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39
Q

What is international unit?

A

This is the amount of enzyme that will catalyze the reaction of one micro molecule of substrate per minute under specific conditions.

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40
Q

What are enzymes quantified relative to?

A

To their activity and not their direct concentration

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41
Q

What is katal measurement?

A

This is an SI measurement defined as the number of moles of substrate converted to product in one second.

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42
Q

What is enzyme kinetics?

A

This is the relationship between enzyme, substrate and product. That is, how quickly the enzyme works on substrate to form product.

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43
Q

Catalytic mechanism is stated as?

A

E + S -> ES -> P + E

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44
Q

List the influencers of enzymatic reactions.

A 
Enzyme concentration 
Substrate concentration 
pH
Temperature 
Cofactor concentration 
Inhibitors
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45
Q

How does enzyme concentration affect enzymatic reactions?

A

The overall rate of enzymatic reaction is proportional to the concentration of enzyme present in the system with constant substrate

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46
Q

How does substrate concentration affect enzymatic reaction?

A

Reaction rate is proportional to substrate concentration if enzyme concentration is kept constant

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47
Q

What is first order kinetics as per substrate concentration?

A

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

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48
Q

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.

A

Zero order kinetics

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49
Q

What is the M-M equation?

A

This is the substrate rate curve that expresses the relationship between substrate concentration and the velocity of the enzymatic .

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50
Q

The M-M equation is expressed as what formula?

A

V = Vmax(S) / Km+S

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51
Q

What is Vmax per the M-M curve?

A

Reaction velocity at maximal substrate concentration

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52
Q

What us Km per M-M curve?

A

M-M constant for a given substrate acting on a given enzyme . Concentration at which half of the maximum velocity is reached

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53
Q

What is the Lineweaver burk plot?

A

It’s a plot that expresses M-M kinetics as a straight line by using reciprocal numbers

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54
Q

What is Vmax with Lineweaver-Burk plot?

A

Vmax is the reciprocal of the y-intercept of the straight line

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55
Q

What is Km with Lineweaver-Burk plot?

A

Km is the negative reciprocal of the x-intercept of the straight line

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56
Q

How does pH affect enzymatic reactions?

A

Reaction rates drop when pH decreases because of the effects of hydrogen ions on active site

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57
Q

How does temperature affect enzymatic reactions?

A

Too high temperatures denature enzymes and reaction rate will drop

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58
Q

How does cofactor concentration affect enzymatic reactions?

A

Increased cofactors concentration increases the velocity of the reaction by the formation of the most active state of the enzyme,

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59
Q

What are inhibitors?

A

Substances that reversibly inhibit normal e Ahmed reactions

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60
Q

How do competitive inhibitors function?

A

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

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61
Q

How do noncompetitive inhibitors function?

A

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
Q

How do uncompetitive inhibitors function?

A

They bind to the ES complex essentially keeping it from forming a product. Both Km and Vmax are changed

63
Q

What supplies the source if most enzymes?

A

Most enzymes are synthesized

64
Q

Do enzymes function intracellularly or extracellularly?

A

Intracellularly

65
Q

What will be the cause of increased plasma/serum levels of enzymes?

A

Cell damage that made enzymes leak into blood

66
Q

Name some enzymes that are secreted and active in extracellular fluid.

A

Amylase
Lipase
Acid phosphate
Coag enzymes

67
Q

I’d study the factors affecting blood levels of enzymes

A

Leakage of enzyme from cells
Clearance of enzymes
Altered enzyme production

68
Q

Where does clearance of enzymes normally occur?

A

In the spleen and liver

69
Q

Why are changes in enzymatic activity not definitively diagnostic?

A

Because there is no completely organ specific enzyme

70
Q

What type of enzyme is creatine kinase?

A

A muscle enzyme

71
Q

List some muscle enzymes.

A

Creatine kinase CK
Lactate dehydrogenase LDH
Aldolase ALD

72
Q

What is Creatine kinase?

A

A transferase that reversibly moves phosphate groups

73
Q

What does CK require for activation?

A

Mg

74
Q

What reaction dies CK catalyze?

A

The reaction that firms ATP in tissues, especially contractile systems

75
Q

In what muscles is CK found?

A

Skeletal muscle
Brain muscle
Cardiac muscle
Others

76
Q

What structure is CK?

A

CK in a dimer

77
Q

How many isoenzymes does CK have?

A

3

78
Q

List the isoenzymes of CK

A

CK B-B
CK B-M
CK M-M

79
Q

Where is CK B-B located?

A

Mostly in the brain. Also prostate, GI and genitourinary tracts

80
Q

What percentage of total CK is CK B-B?

A

1%

81
Q

What is the most increased CK isomer in acute myocardial infarction?

A

CK M-B

82
Q

Where is CK M-B located?

A

Cardiac muscle. Some skeletal

83
Q

What percentage of total CK is CK M-B?

A

<5%

84
Q

Where is CK M-M located?

A

Most.yes skeletal muscle and some cardiac

85
Q

What percentage of total CK is CK M-M?

A

~94%

86
Q

Why is CK normal in acute hepatitis or anemia?

A

Liver and RBCs and almost zero CK activity

87
Q

In what conditions are CK levels elevated?

A

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
Q

What is LDH?

A

Lactose dehydrogenase is an oxidoreductase. A hydrogen transfer enzyme that utilizes NAD as coenzyme.

89
Q

What reaction does LDH catalyze?

A

The interconversion of lactate and pyruvate

90
Q

Where is LDH found?

A

Heart muscle, liver, RBCs, skeletal, kidneys

91
Q

In what conditions are LDH levels high?

A

Pernicious anemia
Crush injuries
Liver disease
Heater attack

92
Q

What is aldolase?

A

This is a lyase found in high amount in striated muscle and liver tissue.

93
Q

What type of reaction does aldolase catalyze?

A

Important reactions in the glycolytic breakdown of glucose to pyruvate/lactate for energy

94
Q

What are the specimen requirements for muscle enzymes?

A

Heparinized plasma or serum

No hemolysis

95
Q

What are the major sources of amylase?

A

Pancreas and salivary glands

96
Q

What are the two isoenzymes of amylase?

A

P-amylase and S-amylase

97
Q

What is amylase?

A

This is a hydrolase that catalyzes the hydrolysis of starches and glycogen to produce simple sugars.

98
Q

Why is amylase present in urine?

A

It is small and can pass through the glomeruli

99
Q

In what conditions are Amylase levels high?

A

Acute pancreatitis
Salivary gland lesions
Some drug usage

100
Q

Amylase levels rise how many hours after onset of symptoms? When does it peak?

A

2-12 hours after onset of symptoms. Peaks at~24 hours

101
Q

What amylase levels remain high for longer between serum and urine?

A

Urine

102
Q

What is lipase?

A

Lipase is a hydrolase enzyme that catalyzes the hydrolysis of glycerol esters to form fatty acids, especially triglycerides

103
Q

Where is lipase found in the body?

A

In the acinar cells of the pancreas with small amounts in stomach and intestine

104
Q

Lipase is examines exclusively to diagnose what condition?

A

Acute pancreatitis

105
Q

Lipase levels rise how many hours after acute pancreatitis attach onset? When does it return to normal?

A

4-8hours and returns to normal 8-14 days later

106
Q

What enzyme is considered the most specific marker of acute pancreatitis?

A

Lipase

107
Q

What type of specimen is required for amylase and lipase studies?

A

Serum or heparinized plasma with no hemolysis or lipemia

108
Q

What other two specimens can be used to test amylase but not lipase?

A

Urine and saliva

109
Q

What type of enzyme is lactate dehydrogenase?

A

Oxidoreductase

110
Q

Where is lactate dehydrogenase found in the body?

A 
Heart muscle
Liver
Rbcs
Skeletal muscle 
Kidneys
111
Q

Lists where the different lactate dehydrogenase isoenzymes are located?

A 
LD1 RBCs and heart
LD2 RBCs, heart and WBCs
LD3 Lungs
LD4 kidneys, pancreas, placenta
LD5 Liver, skeletal muscle
112
Q

Why is lactate dehydrogenase measurement common in hematology and oncology?

A

Because lactate dehydrogenase is elevated in megaloblastic anemia and some cancers

113
Q

What are cholinesterases?

A

A group of hydrolases that hydrolyze the esters of choline

114
Q

Why is cholinesterase important?

A

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
Q

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

A

Cholinesterase

116
Q

What are the two types of cholinesterase?

A 
Acetylcholinesterase (true cholinesterase)
Acylcholine acylhydrolase (pseudocholinesterase)
117
Q

Which one of the two types of cholinesterase is considered most clinically significant?

A

Acylcholine acylhydrolase

118
Q

AChe is found in

A

Brain cells, RBCs, nerve cells

119
Q

CHE is found in

A

Liver, pancreas, heart, serum

120
Q

CHE is decreased in what conditions?

A

Liver disease
Insecticide poisoning
Genetics

121
Q

Where is G6PD located in the body?

A

Adrenal glands, spleen, thymus, RBCs and lymph nodes

122
Q

What is G6PD?

A

It’s an oxidoreductase that catalyzes the oxidation of G6P to form 6-phosphoglucuronate

123
Q

Why is NADPH production important during oxidation of G6P?

A

To maintain glutathione (GSH) level in RBC

124
Q

What is GSH?

A

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
Q

Deficiency in G6PD results in what?

A

Hemolytic anemia

126
Q

What is ACP used for?

A

To assess bone issues

127
Q

This enzyme is a marker for bone resorption

A

Acid phosphatase

128
Q

What is the heart?

A

This is a four chambered muscular organ with two sides for pumping

129
Q

What is the pumping action of the heart responsible for?

A

Circulation of blood through arteries and veins

130
Q

What quantity of blood does the heart pump!

A

6L of blood per minutes or ~85mL per beat

131
Q

What is another name for the atria?

A

Hallway

132
Q

What is another name for the ventricles?

A

Cavity of little belly

133
Q

What moves into the right atrium from the body?

A

Deoxygenated blood

134
Q

What happens with the left atrium?

A

Oxygenated blood moves into the left atrium from pulmonary veins of lungs

135
Q

What does the right ventricle do?

A

Pumps deoxygenated blood into the lungs

136
Q

What does the left ventricle do?

A

Pumps oxygenated blood into the aorta and subsequent large arteries of the head, trunk and extremities

137
Q

Which ventricle is considered the strongest one?

A

The left ventricle

138
Q

What divides the atria?

A

Interatrial septum

139
Q

What is the use of valves?

A

Prevent the back flow of blood through the heart

140
Q

What separates the ventricles?

A

Intraventricular septum

141
Q

What are coronary arteries?

A

These are vessels on the surfaces of the heart that supply blood to the cardiac muscle

142
Q

Why does cardiac muscle require a constant blood supply?

A

Due to strict oxygen requirements

143
Q

What happens if coronary arteries are blocked?

A

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
Q

What are the symptoms of cardiac ischemia?

A

Chest pain
Arrhythmia
Heart failure/MI

145
Q

What is heart failure / MI?

A

This is when the heart does not pump enough blood to meet the O2 needs of peripheral tissue

146
Q

What are some cardiac diseases that can cause heart failure?

A

CHF
CAD; ACS
Cardiomyopathy

147
Q

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

A

Coronary artery disease

148
Q

What is the difference between angina and AMI?

A

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
Q

What arev5he two types of AMI?

A

NSTEMI

STEMI

150
Q

What is angina pectoris?

A

Deficiency of oxygen to cardiac muscle from incomplete obstruction of coronary arteries

Clinical Chem II (10 decks)

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