SIMPLE EUTECTIC SYSTEMAND

ENZYME CATALYSIS

By-ANEETTA DAVISM15NT01

SIMPLE EUTECTIC SYSTEM (PB AND AG SYSTEM)

SIMPLE EUTECTIC SYSTEM

Eutectic comes from a Greek word EUTEKTOS

EU TEKTOS

GOOD MELTING

EASILY MELTING

TWO COMPONENT SYSTEM

o A two component system can be defined as one in which it is possible to express the composition of all the phases in terms of two substances.

o In a two component system, solid – liquid equilibria is considered as they are unaffected by the changes in pressure; such systems are called condensed system which are studied at one atmosphere.

Therefore, for condensed state the phase rule equation is F’=C-P+1

oIf two substances are completely miscible in liquid state but immiscible in solid state forms a simple eutectic system.The mixture that has the lowest melting point is called eutectic mixture and the temperature at which it crystallizes as a whole is called eutectic temperature.

LEAD AND SILVER SYSTEMo Lead and silver are completely miscible

in liquid state.o Molten Pb and Ag are miscible in all

proportion a homogenous solution is produced. The four possible phases are:

Solid Ag Solid Pb Solution(Ag + Pb) Vapor

A

O

B

L N

LIQUID MELT (Pb+Ag)

LIQUID+SOLID Ag

LIQUID + SOLID Pb

EUTECTIC + SOLID Pb

EUTECTIC + SOLID Ag

Composition

Temperature

327

303

Freezing or melting point curve of lead

961

Freezing point or melting point curve of silver

Eutectic point

2.5% Ag and 97.5% PbThe phase diagram for Pb-

Ag system

ENZYME CATALYSIS

Catalysts CatalysisThe substance that can alter The phenomenon or the rate of a reaction. process is called catalysis.

PROPERTIES OF CATALYSTS It alters the rate of reaction. It remains unchanged in mass and chemical composition after the completion of the reaction. A small amount is enough to bring about a reaction between large reactants. It is very specific.

TYPES OF CATALYSIS

CATALYSIS

Homogenous Heterogeneous

The catalysts and reactants are in the

same phase.

The catalysts and reactants are in different phases.

ENZYME CATALYSIS

Enzyme is a biological catalyst which is a protein.

The increase in the rate of a chemical reaction by the active site of a protein is called enzyme catalysis.

THE ACTIVE SITE

o Enzymes are typically HUGE proteins, yet only a small part are actually involved in reaction.

o The active site has two basic components.

catalytic site binding site

Catalytic siteWhere reaction

occursBinding

Siteholds

substrate in

place Substrate

Enzyme

THE ACTIVE SITE

CATALYTIC POISONING

o It is the substance that reduces the effectiveness of a catalyst in a chemical reaction.

Example: Carbon on silica-alumina catalyst in

the cracking of petroleum

AUTOCATALYSIS

o If one of the reaction products is also a reactant and therefore a catalyst in the same reaction then the chemical reaction is said to be autocatalytic.

THEORIES OF CATALYSIS

o The two main theories of catalysis are;

Intermediate compound formation theory

Adsorption theory

INTERMEDIATE COMPOUND FORMATION THEORY

A + [CATALYST] [INTERMEDIATE][INTERMEDIATE] + B PRODUCT +

CATALYST

2SO2 + O2 [NO] 2SO3

Example:2NO + O2 2NO2

NO2 + SO2 SO3 + NO

ADSORPTION THEORY

A(g

)

+ B(g) C(g

)

+D(g)

CATALYST

BAA B

A- - ->B

C

D

THEORIES OF ENZYME CATALYSIS

o The two main theories of enzyme catalysis are:

Lock and key model Induced fit model

LOCK AND KEY THEORY

This model was given my Emil Fischer.Enzyme is “lock” and Substrate is the “key”.

Substrate structure must fit into enzyme’s structure.

INDUCED FIT MODEL

Active site may not fit substrate.

Site must change in order to form the complex.