ENZYME PT.2 (FINALS)

Question 1

Three (3) types of specificity of enzymes:

Answer 1

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

Question 2

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

Answer 2

Optical Specificity

Question 3

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

Answer 3

Stereospecificity

Question 4

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

Answer 4

Reaction Specificity

Question 5

2 types of Substrate Specificity:

Answer 5

1) Absolute Specificity
2) Relative Specificity

Question 6

— comparatively rare such as urease which catalyzes hydrolysis of urea

Answer 6

Absolute Specificity

Question 7

2 types of Relative Specificity

Answer 7

1) Group Specificity
2) Bond Specificity

Question 8

— 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.

Answer 8

Group Specificity

Question 9

— 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.

Answer 9

Bond Specificity

Question 10

Factors affecting enzyme action

Answer 10

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

Question 11

— 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

Answer 11

Effect of Temperature

Question 12

— 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

Answer 12

Effect of pH

Question 13

— enzymatic reaction is directly proportional to the enzyme concentration

Answer 13

Effect of Enzyme Concentration

Question 14

— 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

Answer 14

Effect of Product Concentration

Question 15

— 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

Answer 15

Effect of Substrate Concentration

Question 16

— certain enzymes is dependent of metal ion activators and coenzymes

Answer 16

Effect of Activators and Coenzyme

Question 17

— 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.

Answer 17

Effect of Modulators and Inhibitors

Question 18

— 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

Answer 18

Effect of Time

Question 19

— 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.

Answer 19

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

Question 20

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

Answer 20

The effect of a Substrate Concentration on Enzyme-Catalyzed Reaction

Question 21

2 stages of enzyme-catalyzed reaction:

Answer 21

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)

Question 22

— The part of the enzyme that binds with the substrate

Answer 22

Active Site

Question 23

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

Answer 23

True

Question 24

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)

Answer 24

False (it is complementary)

Question 25

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

Answer 25

False (it attracts)

Question 26

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

Answer 26

True

Question 27

2 Models Used in Enzyme

Answer 27

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

Question 28

— 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)

Answer 28

Lock-and-Key Model

Question 29

— 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

Answer 29

Induced Fit Model

Question 30

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.

Answer 30

Mechnism of Enzymes Catalysis

Question 31

4 Types of Catalytic Mechanisms that enzymes employ:

Answer 31

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

Question 32

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

Answer 32

Enzyme Inhibition

Question 33

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

Answer 33

Enzyme Inhibitor

Question 34

— 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

Answer 34

Competitive Enzyme Inhibitor

Question 35

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.

Answer 35

False (Decrease in enzyme activity)

Question 36

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.

Answer 36

True

Question 37

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.

Answer 37

True

Question 38

— 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.

Answer 38

Noncompetitive Enzyme Inhibitor

Question 39

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.

Answer 39

False ( it can still occupy)

Question 40

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.

Answer 40

False (increasing the concentration)

Question 41

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

Answer 41

True

Question 42

— 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

Answer 42

irreversible Enzyme Inhibitor

Question 43

— 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.

Answer 43

Regulation of the Enzyme Activity

Question 44

— 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.

Answer 44

Allosteric Enzymes

Question 45

2 Allosteric Enzymes

Answer 45

1) Negative Allosterism 2) Positive Allosterism

Question 46

— inihibit enzyme action

Answer 46

Negative Allosterism

Question 47

— stimulate enzyme action

Answer 47

Positive Allosterism

Question 48

—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,

Answer 48

Proenzyme

Question 49

—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

Answer 49

Protein Modification

Question 50

— 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.

Answer 50

Feedback Control

Question 51

— 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

Answer 51

Feedback Control

Question 52

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

Answer 52

Enzyme in Medical Diagnosis and Treatment

Question 53

— 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

Answer 53

Diagnostic Enzymes

Question 54

— 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

Answer 54

Serum

Question 55

Measurement of these enzymes is important for: (2)

Answer 55

Diagnosis and Prognosis of Disease

Question 56

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

Answer 56

Diagnosis of Disease

Question 57

— Follow up treatment pre and post measurement of enzymes

Answer 57

Prognosis of Disease

Question 58

— 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.

Answer 58

Sources of Non-Functional Enzymes

Question 59

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

Answer 59

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