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★BIOCHEM LEC > ENZYME PT.2 (FINALS) > Flashcards

ENZYME PT.2 (FINALS) Flashcards

1
Q

Three (3) types of specificity of enzymes:

A

1) Stereochemical Specificity
2) Reaction Specificity
3) Substrate Specificity

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2
Q

— only one of the isomers which acts as a substrate for an enzyme action.

A

Optical Specificity

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3
Q

— due to apoenzyme part of holoenzyme.
— the reaction produces a particular stereoisomer depending on the starting material.

A

Stereospecificity

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4
Q

— substrate can undergo many reactions. but in this specificity of enzyme, one enzyme can catalyze only one of the various reactions.

A

Reaction Specificity

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5
Q

2 types of Substrate Specificity:

A

1) Absolute Specificity
2) Relative Specificity

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6
Q

— comparatively rare such as urease which catalyzes hydrolysis of urea

A

Absolute Specificity

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7
Q

2 types of Relative Specificity

A

1) Group Specificity
2) Bond Specificity

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8
Q

— refers to the ability of an enzyme or molecule to act on a specific group of similar compounds, rather than a single specific substrate.
— examples are Trypsin, Chymotrypsin.
— Trypsin hydrolyzes the residues of only lysine and arginine, while Chymotrypsin hydrolyzes residues of only aromatic amino acids.

A

Group Specificity

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9
Q

— refers to the ability of an enzyme to catalyze a reaction by targeting a specific type of chemical bond in a substrate.
— observed in case to proteolytic enzymes, glycosidases, and lipases which act on peptide bonds, glycosidic bonds, and ester bonds.

A

Bond Specificity

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10
Q

Factors affecting enzyme action

A

1) Effect of Temperature
2) Effect of pH
3) Effect of Enzyme Concentration
4) Effect of Product Concentration
5) Effect of Substrate Condition
6) Effect of Activators and Coenzyme
7) Effect of Modulators and Inhibitors
8) Effect of Time

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11
Q

— enzyme is most active on its optimum temperature
— temperature increases the total energy of the chemical system with the result the activation energy is increased
— enzyme activity decreases when the temperature of reaction is below or above optimum temperature
— increase in temperature also causes denaturation of enzymes

A

Effect of Temperature

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12
Q

— enzymatic reaction depends on the pH of the medium
— optimum pH is 4-9
— hydrogen ions in the medium may alter ionization of
active site or substrates (ionization is a requirement for
ES complex)
— pH may influence separation of coenzyme from
holoenzyme complex

A

Effect of pH

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13
Q

— enzymatic reaction is directly proportional to the enzyme concentration

A

Effect of Enzyme Concentration

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14
Q

— products formed as a result of enzymatic reaction may accumulate, and this excess of product may lower the enzymatic reaction by occupying the active site of the enzyme
— it is also possible that under certain conditions of high concentration of products, a reverse reaction may be favored forming back the substrate

A

Effect of Product Concentration

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15
Q

— reaction is directly proportional to the substrate
concentration, but only true up to a certain concentration after which the increasing
concentration of substrate does not further increase
the velocity of the reaction

A

Effect of Substrate Concentration

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16
Q

— certain enzymes is dependent of metal ion activators and coenzymes

A

Effect of Activators and Coenzyme

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17
Q

— Whenever the active site is not available for binding of the substrate, the enzyme activity may be reduced.
— Substances which stop or modify enzymatic reaction are inhibitors and modulators which can adversely affect the rate of enzymatic reaction.

A

Effect of Modulators and Inhibitors

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18
Q

— The time required for completion of an enzyme
reaction increases with decreases temperature from
its optimum.
— Under the optimum conditions of pH and
temperature, time required for enzymatic reaction is
less

A

Effect of Time

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19
Q

— To speed up chemical reaction, it changes the path by which the reaction occur, providing a lower energy route for the conversion of the substrate into the
product, the substance that result from the enzyme-
catalyzed reaction.

A

The effect of the Enzymes on the Activation Energy of a Reaction

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20
Q

— The rates of uncatalyzed chemical reactions often double every time the substrate concentration is doubled.

A

The effect of a Substrate Concentration on Enzyme-Catalyzed Reaction

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21
Q

2 stages of enzyme-catalyzed reaction:

A

A. Formation of the enzyme substrate complex
B. Conversion of the substrate to product and the release of the product and enzymes from the resulting
enzyme-product complex. (rate-limiting steps)

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22
Q

— The part of the enzyme that binds with the substrate

A

Active Site

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23
Q

T/F : Enzyme active sites are pocket or cleft in the surface of the enzyme.

A

True

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24
Q

T/F: The shape of the active site is NOT complementary to the shape of the substrate. (or Fits nearly into the active site of the enzyme)

A

False (it is complementary)

25
Q

T/F : An enzyme does not attracts and holds its substrate by weak, non-covalent interaction.

A

False (it attracts)

26
Q

T/F : The conformation of the active site determines the
specificity of the enzyme because only the substrate
that fits into the active site will be used in a reaction

A

True

27
Q

2 Models Used in Enzyme

A

1) Lock-and-Key Model
2) Induced Fit Model

28
Q

— By Emil Fischer in 1894.
— The specific action of an enzyme with a single substrate can be explained using a Lock and Key
— In this analogy, the lock is the enzyme and the key is the substrate.
— Only the correctly sized key (substrate) fits into the key hole (active site) of the lock (enzyme)

A

Lock-and-Key Model

29
Q

— By Daniel E. Koshland, Jr. in 1958
— It assumes that the substrate plays a role in determining the final shape of the enzyme and that the enzyme is partially flexible.
— This explains certain compounds can bind to the enzyme but do not react because the enzyme has been distorted too much.
— Other molecules may be too small to induce the proper substrate is capable of inducing the proper alignment of the active site

A

Induced Fit Model

30
Q

Enzyme catalyze reactions by interacting with
the substrate and the subsequent transition
state. These interaction release energy and
therefore stabilize the transition state, which
ultimately lower the activation energy of the
reaction.

A

Mechnism of Enzymes Catalysis

31
Q

4 Types of Catalytic Mechanisms that enzymes employ:

A

1) Covalent Catalysis
2) Catalysis by Proximity and Orientation
3) Acid-Base Catalysis
4) Metal Ion Catalysis

32
Q

— rates of enzyme-catalyzed reactions can be
decrease by a group of substances called
inhibitors

A

Enzyme Inhibition

33
Q

— is a substance that slows or stops the normal catalytic function of an enzyme by binding to it

A

Enzyme Inhibitor

34
Q

— is a molecule that sufficiently resembles an enzyme substrate in shape and charge distribution that it can compete with the substrate for occupancy of the enzyme’s active site

A

Competitive Enzyme Inhibitor

35
Q

T/F: When a competitive inhibitor binds to the enzyme active site, inhibitor remains unchanged (no reaction occurs), but its physical presence at the site prevents a normal substrate molecule from occupying the site – result is increase in enzyme activity.

A

False (Decrease in enzyme activity)

36
Q

T/F: (Reversible Competitive Inhibitor)
Formation of enzyme-competitive inhibitor is a reversible process because it is maintained by weak interactions (H bonds). With time (fractions of seconds), the complex breaks up.

A

True

37
Q

T/F: (Reversible Competitive Inhibitor)
The empty active site is then available for a new occupant. Substrate and inhibitor again compete for the empty active site.
Thus, the active site of an enzyme binds either inhibitor or normal substrate on a random basis. If inhibitor concentration is greater than substrate concentration, the inhibitor dominates.

A

True

38
Q

— is a molecule that decreases enzyme activity by binding to a site on an enzyme other than the active site.
— Binding o these inhibitors modifies the shape of the active site in much the same way that the binding of an allosteric effector does.

A

Noncompetitive Enzyme Inhibitor

39
Q

T/F: In noncompetitive enzyme inhibitor, substrate cannot occupy the active site, but the presence of the inhibitor causes a change in the structure of the enzyme sufficient to prevent the catalytic groups at the active site from properlyeffecting their catalyzing action.

A

False ( it can still occupy)

40
Q

T/F: (Noncompetitive Enzyme Inhibitor)
Since this binding is nonspecific, these inhibitors inactivate a broad range of enzyme unlike in competitive inhibition, decreasing the concentration of the substrate does not completely overcome the inhibitory effect in this case.

A

False (increasing the concentration)

41
Q

T/F: (Noncompetitive Enzyme Inhibitor)
— However, lowering the concentration of a noncompetitive inhibitor does free up many enzymes, which then return to normal activity

A

True

42
Q

— is a molecule that inactivates enzymes by forming a strong covalent bond to an amino acid side-chain group at the enzyme’s active site
— inhibitors do not have structures similar to that of enzyme’s normal substrate
— inhibitor-active site bond is sufficiently strong that addition of excess substrate does not reverse the inhibition process

A

irreversible Enzyme Inhibitor

43
Q

— It is often regulated by the cell. Often the reason for this is to conserve energy because if the cell runs out of chemical energy, it will die; therefore many mechanism exist to converse energy.

A

Regulation of the Enzyme Activity

44
Q

— Enzymes that have more than one a single site. It has an active sites that can be altered by binding of a small molecules called effector molecules or regulators.

A

Allosteric Enzymes

45
Q

2 Allosteric Enzymes

A

1) Negative Allosterism
2) Positive Allosterism

46
Q

— inihibit enzyme action

A

Negative Allosterism

47
Q

— stimulate enzyme action

A

Positive Allosterism

48
Q

—The production of the enzyme in an active
form. The proenzyme is converted by proteolysis to the active from when it has reached the site of its activity,

A

Proenzyme

49
Q

—This is a process in which a chemical group is covalently added to or removed from the protein. This covalent modification either activates the enzyme or turn it off

A

Protein Modification

50
Q

— Enzymes are often regulated by environmental conditions.
— It is an enzyme regulation process in which
formation of a product inhibits an earlier
reaction in the sequence.
— The reaction product of one enzymes may
control the activity of another, especially in a
complex system in which enzymes work
cooperatively.

A

Feedback Control

51
Q

— The final product in the chain may
inhibit the activity of the first enzyme. When the concentration of the final product is low, all of the reactions proceed rapidly.
— As the concentration increases, however the enzyme 1 becomes inhibited and eventually stops.
— The accumulation of the final product serves as a message that tells enzyme 1 to shut down because the cell has enough final product for its present needs

A

Feedback Control

52
Q

— Assay of enzymes present in blood plasma or serum have been routinely carried out in clinical chemistry laboratories

A

Enzyme in Medical Diagnosis and Treatment

53
Q

— refers to the enzymes
that are used directly or as components of the assay system for the determination of number of substances
— Changes in the concentrations of various
biomolecules are indications of abnormal
metabolic activities,infections,infectious and
non-infectious diseases and inflammatory
conditions.
— Use to detect and quantify certain substances

A

Diagnostic Enzymes

54
Q

— is the component that is neither a blood cell
— it does not contain white or red blood cells)
nor a clotting factor; it is the blood plasma with the fibrinogens removed.
— includes all proteins not used in blood clotting (coagulation) and all the electrolytes, antibodies, antigens and hormones

A

Serum

55
Q

Measurement of these enzymes is important for: (2)

A

Diagnosis and Prognosis of Disease

56
Q

— as disease of different organs cause elevation of different plasma enzymes.

A

Diagnosis of Disease

57
Q

— Follow up treatment pre and post measurement of enzymes

A

Prognosis of Disease

58
Q

— Cell damage
— Obstruction of normal pathways:
ex: obstruction of bile duct increases
alkaline phosphatase
— Increase of the enzyme synthesis: ex
Bilirubin increases the rate of synthesis
of alkaline phosphatase in obstructive
liver disease.
— Increased permeability: eg hypoxia.

A

Sources of Non-Functional Enzymes

59
Q

How it is measure? (Sources of non-functional enzymes)

A

— It is measure through blood samples.
— Then blood samples where undergo Electrophoresis, chromatographic techniques
and isoelectric focusing.

★BIOCHEM LEC (5 decks)

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