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Enzymes Flashcards

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1
Q

Name an isomerase enzyme

A

Triose phosphate isomerase

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2
Q

The protein component in compound protein enzymes

A

Apoenzyme

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3
Q

The prosthetic group is termed as

A

Co-enzyme

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4
Q

Coenzymes may be involved in the transfer of hydrogen , eg:

A

NAD FAD FMN

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5
Q

Coenzymes involved in the transfer of groups other than hydrogen

A

Amino group by PLP , Hydroxyethyl group is transferred by TPP

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6
Q

Metal required for the activity of lipase

A

Calcium

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7
Q

State the Michaelis- Menten theory

A

That an enzyme combines with the substrate to form an enzyme substrate complex( reversible reaction )which breaks down to give the product (irreversible reaction .
Write as reversible and irreversible equation

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8
Q

Lock and key theory to explain the mechanism of enzyme action also called

A

Fischer’s template

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9
Q

Induced fit theory used to explain the mechanism of enzymes is also known as

A

Koshland’s induced fit theory

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10
Q

Define active site

A

Area of an enzyme where catalysis occurs

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11
Q

What are catalytic residues

A

Amino acid residues of the enzyme involve directly in the inning of the substrate

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12
Q

Enzyme activity is influenced by

A

Enzyme conc. , substrate conc.,temp , pH , presence of inhibitors

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13
Q

What does the km value denote

A

Affinity of the enzyme to the substrate

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14
Q

Relation of affinity and km value

A

Inversely proportional

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15
Q

Example of stereoisomerism

A

Lactate dehydrogenase

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16
Q

Explain , enzymes are diffusion limited

A

Rate of reaction is limited by the rate at which substrate molecules diffuse through solution and reach the active site of the enzyme

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17
Q

Examples of multi enzyme complexes

A

FAS (Fatty Acid Synthase
Pyruvate dehydrogenase
Alpha keto glutarate dehydrogenase
Acetyl coA carboxylase
Glycine cleavage system
Pyruvate carboxylase
Pyramiding nucleotide synthessi

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18
Q

NAD+ OR NADP+ Dependent enzymes are assayed by

A

Spectrophotometery

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19
Q

Why are NAD and NADP+ dependent enzymes assayed by spectrophotometer

A

As the reduced form of. These coenzymes will absorb light at a wavelength of 340nm
But oxidized forms will not absorb light

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20
Q

Enzyme activity is expressed as

A

Micro moles of substrate converted to product perminute under specifies assay conditions

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21
Q

Define the standard unit or international unit of enzyme activity

A

Amount of enzyme required to convert 1 micoromole of substrate per minute per litre of sample at 25°C

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22
Q

Glucose oxidase is absolutely specific to the high substrate

A

Beta -D-glucose

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23
Q

Urease hydrolyses urea to

A

Ammonia and co2

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24
Q

An example of bond specific peptide sets

A

Trypsin (hydrolysis binds formed by carboxyl groups of arginine or lysine residues in any protein

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25
Define group specificity
One enzyme can cataclysm the same reaction on a group ofstructurally similar compounds
26
Name a group specific enzyme
Hexokinase - catalyze phosphorylation of glucose , galactose and mannose
27
Name a non protein enzyme and it’s enzyme activity
Ribozyme(RNA molecule with enzyme activity ) Which catalyzes cutting of nascent mRNA or primary transcript
28
Stereospecificity shown by human enzymes
Specific for L-amino acids and D-sugars
29
Examples of stereospecific enzyme reactions
Lactate dehydrogenase acts on pyruvate to form “L-lactate !not D Fumarse fumaric acid to malic acid , cis form male if acid not acted upon
30
Salivary amylase show higher activity in the presence of which inorganic ion
Chloride
31
Conversion of trypsinogen to active trypsin
By splitting a single peptide bond and removal of a small polypeptide chain . Results in unmasking of the active center
32
The process of activation of chymotrypsinogen by trypsiongen
33
Which law explains the effect of concentration of products
Law of mass action
34
What happens when one enzyme of a metabolic pathway is blocked due to inborn metabolism
A +E1 —->B +E2—>C xE2—-> D C will accumulate in the absence of E3 which will in turn inhibit E2 , in due time while pathway is blocked
35
Lineweaver burk equation
V = vmas(s) /km+ (s)
36
Shape of Curve of effect of temperature on enzyme activity
Bell shaped
37
Define optimum temperature
The temp at which max amount of substrate is converted to product per unit ime
38
How does increasing temp increase activity
Increases velocity of enzyme reaction so their collision probability is increased . More molecules get activation energy
39
What is temperature coefficient
Factor by which the rate of catalysis is increased for a a rise in 10°C Generally rate will be doubled
40
Why is the curve of temp bell shaped
Temp is more than 50°C , heat desaturation and loss of tertiary structure of protein occurs , so enzyme activity his decreased
41
Optimum temp for human enzymes
37 degree Celsius
42
Certain bacteria have optimum temp
100°C living in hot springs
43
Effect of pH on catalysis , graph is
A bell shape curve
44
How does the pH effect the catalytic activity
pH decides the net charge on the amino acid residues at the active site . The net binding and catalytic activity . The net charge on the enzyme protein would influence substrate binding and catalytic activity. They are ampholytes with charges , alters enzyme activity by altering the dissociation activity
45
Optimum ph may vary with
Temperature Concentration of substrate Presence of ions
46
Optimum pH of enzymes
6 to 8
47
Exceptions of optimum pH of enzymes
Pepsin(pH 1-2) Alkaline phosphatase (optimum pH 9- 10 Acid phosphatase (optimum pH 4-5)
48
Km for glucokinase
10mmol/L
49
Km value of hexokinase
0.05 m mol/L (therefore 50% molecules of hexkinase are saturated even at a low conc of glucose )
50
What does the difference in Km of glucokinase and hexokinase tell us
Hexokinase has more affinity for glucose than. Glucokinase
51
What is km value
Affinity of the enzyme to the substrate , Is the substrate con at half-maximal velocity . It denotes that 50% of enzyme molecules are bound with substrate molecules at that particular substrate concentration
52
What is the km value independent of
Enzyme conc. When enzyme conc. is doubled , max doubles . But 1/2vmax remains same (That is irrespective of the enzyme conc , 50% molecules are bound to substrate at the particular substrate conc
53
Coenzyme that acts as a cosubstrate
Pyruvate converted to lactate in the presence of lactate dehydrogenase and NADH +H+ To NAD+
54
Example of an end product assay
Disodium phenyl phosphate (substrate ) in the presence of alkaline phosphatase to form phenol + 4amino pyrine
55
The more intense color in end point assay shows
More amount of chemical reaction or enzyme activity
56
If velocity is plotted against substrate conc , a what type of curve is achieved
A typical curve ,
57
If velocity is plotted against substrate conc , a typical curve is achieved . Why
As substrate conc increases in the initial phases ,velocity also increases but the curve flattens afterwards
58
What does the maximum velocity obtained represent
Represents the maximum reaction rate attainable in presence of excess substrate (at substrate saturation level )
59
Relation btw enzyme conc and rate of reaction /velocity
Directly proportional when sufficient substrate is present
60
Velocity of reaction is increased proportionately with the concentration of enzyme, provided substrate concentration is unlimited . This property is used for
Determining the level of particular enzyme in plasma , serum or tissues (sample ). Known volume of serum is incubated with substrate for a fixed time , then reaction is topped and product quantified (end point method )since product formed proportional to enzyme con , latter will be assayed
61
Cofactor is
Collective term for coenzymes and cofactors
62
Active center of an enzyme contains with amino acid residue
Serine residue
63
Mistake of Fisher’s template theory
Envisaged a rigid structure for enzymes , could not explain flexibility shown by enzymes
64
What does koshland’s induced fit theory state
Conformational changes occur at the active site of enzymes which leads to more secondary binding and conformational changes
65
Catalytic or active site of ribonuclease
Lies within the hydrophobic cleft . With 7th and 41st lysine on one side , other side 12th and 119th histidine on the opposite side of the binding ofuridylic acid acid .
66
Active groups are brought to specific orientation by
Tre
67
Example of uncompetitive inhibition
Inhibition of placental alkaline phosphatase (Regan iso-enzyme) by phenylalanine b
68
Examples of non competitive inhibition
Cyanide inhibits cytochrome oxidase. b. Fluoride will remove magnesium and manganese ions and so will inhibit the enzyme, enolase, and consequently the glycolysis. c. Iodoacetate would inhibit enzymes having -SH group in their active centers. d. BAL (British Anti-Lewisite; dimercaprol) is used as an antidote for heavy metal poisoning. The heavy

Biochemistry (10 decks)

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