Enzymology: Catalysis

Question 1

Enzyme Def.

Answer 1

Proteins that function as biological catalysts, altering the rate of the reaction without being changed itself

Question 2

Why enzymes are important

Answer 2

Chemical reactions require them to proceed at effective rate for body function. Direct all metabolic events in body (thus any enzyme failure results in reduced body function)

Question 3

Black Urine Disease Outline

Answer 3

Defect in enzyme homogenistate 1,2- deoxygenase necessary for processing cdertain amino acids. Homogenestic acid builds up in body damaging tissues and coloring urine black

Question 4

Enzyme Diagnostic Tool Functions

Answer 4

Enzyme presence/absence in patient samples can be used as indicators of disease. Eg Liver tests for aminotransferase diagnosing hepatocellular injury, biliary obstruction or hypothyroididm

Question 5

Enzymes Shape and Composition

Answer 5

Globular with active site shape complementary to 1 specific substrate. Some contain a co-factor (non-protein component). Localise to 1 spot

Question 6

Types of Enzymes

Answer 6

Oxidoreductase, Transferase, Hydrolases, Lyases, Isomerases and Ligases

Question 7

Oxidoreductase Function

Answer 7

Adds/ removes H+ from molecules

Question 8

Transferase Functions

Answer 8

Transfers C-, N- or P-

Question 9

Hydrolases Function

Answer 9

Cleaves bonds and adds -OH

Question 10

Lysases Function

Answer 10

Cleaves C-C, C-S and C-N bonds

Question 11

Isomerase Function

Answer 11

Changes isometric shape

Question 12

Ligases Function

Answer 12

Forms new bonds

Question 13

Active Site Outline

Answer 13

Specific chape to only bind a few substrates. Protects substrate from external environment and holds it in place

Question 14

How enzyme and substrate combine

Answer 14

electroststic attraction (opposite charges) and complementary shape

Question 15

How enzyme converts substrate into product

Answer 15

Substrate pushed into ‘transition state’ (high energy) and bonds change within substrate

Question 16

How do enzymes speed up the rate of the reaction

Answer 16

They lower the activation energy

Question 17

Enzyme Initial Rate

Answer 17

Slowest. Low substrate conc

Question 18

Enzyme Optimum Rate

Answer 18

Medium Rate. Enzymes at their most effuicent. Substrate to product ratio is pretty much equal

Question 19

Enzyme Maximum Rate

Answer 19

Fastest rate possible. Significantly higher substrate then product concentration

Question 20

Enzyme Rate (V) Def.

Answer 20

Number of substrate molecules converted to product per unit time. Unit: micro-mole per minute

Question 21

Michaelis-Menton Plot Outline

Answer 21

x-axis: Substrate conc. y-axis: velocity. Begins almost linear but begins to plateu when reaching Vmax. Established under conditions of fixed temp and pH

Question 22

Vmax Def.

Answer 22

The fastest an enzyme can convert substrate to product.

Question 23

Km (Michealis Constant) Def.

Answer 23

The substrate concentration when we reach 50% Vmax. This indicates the affinity an enzyme has for it’s substrate. Lower Km (less solute conc required for 50% Vmax) = higher affinity

Question 24

Practical Applications of Km

Answer 24

Defines optimal solute concentration to use in lab to measure enzyme reactions

Question 25

Substrate Concentration Notation

Answer 25

[S]

Question 26

Michaelis-Menton Plot to Lineweaver-Burk Plot Conversion

Answer 26

A curved line to straight. Line now crosses both x and y axises enabling more accurate readings of Vmax and Km. Equation of line is inverted to reciprocal

Question 27

Lineweaver-Burk Line plot

Answer 27

x-axis: 1/[S], y-axis: 1/V0

Question 28

Lineweaver-Burk Plot y =mx + c

Answer 28

1/V0 = (Km/Vmax)(1/[S]) + 1/Vmax

Question 29

5 Factors Regulating Enzymes

Answer 29

Temp, pH, substrate conc., cofactor/coenzyme and enzyme inhibition

Question 30

Temperature outline

Answer 30

Enzymes operate best at 35-40 degrees C. Velocity increases proportionally with temp until point of denaturation is reached (irreversable)

Question 31

pH Outline

Answer 31

Optimum varies with different enzymes. Denaturation can occur

Question 32

What types of enzymes have a sigmoid (slow start, accelarion, plateus at end) curve and why

Answer 32

Allosteric. HAs multiple sub units + active sites leading it to not obey Michaelis Kinetics

Question 33

Cofactor Def.

Answer 33

Inorganic metal ions attached to enzymes

Question 34

Coenzymes Def.

Answer 34

Organic molecules (eg vitamins)

Question 35

Apoenzyme Def.

Answer 35

Enzyme without cofactor. Inactive

Question 36

Holoenzyme Def.

Answer 36

Enzyme with cofactor. Active

Question 37

Prosthetic Enzyme Def.

Answer 37

Coenzyme tightly bound to enzyme

Question 38

Inhibitor Def.

Answer 38

Substance that diminishes the velocity of an enzyme-catalyzed reaction. 2 Types

Question 39

Irreversible Inhibitor Def.

Answer 39

Form covalent bonds. Can’t reagin activity

Question 40

Reversible Inhibitor Def.

Answer 40

Non-covalent bonds. Dilution of enzyme-inhibitor complex recovers activity. 2 Types

Question 41

Competitive Reversable Inhibitors

Answer 41

Bind to active sites. Preventing enzyme bonding

Question 42

Non-competitive Reversable Inhibitors

Answer 42

Doesn’t bind to active sites but prevents enzyme converting substrate into product