By: Fitri Suri Solehah bte Hj Mat Usen

4 UTM

4.54.5 ENZYMES ENZYMES

LEARNING OUTCOMES

State what enzyme are Explain why enzymes are needed in life processes List the general characteristics of enzymes Relate the name of enzyme to substrate State sites where enzymes are synthesised State the meaning of intracellular enzymes and extracellular enzymes Explain the involvement of specific organelles in the production of

extracellular enzymes

Explain the effects of pH,temperature,enzyme concentration and substrate concentration on enzyme activity

Explain the mechanism of enzyme action Relate the mechanism of enzyme action with pH,temperature,enzyme

concentration and substrate concentration Explain the uses of enzymes in daily life and industry using examples

Example of enzymeExample of enzyme

Role of enzymes in organismsRole of enzymes in organisms

Enzymes are protein Enzymes are biological catalyst that speed up the rate of biochemical

reactions in the cells Chemical reactions that occur within a living organism are called

metabolism Metabolic reaction starts with the substrate and ends with product

General characteristics of enzymesGeneral characteristics of enzymes

Speed up the rates of chemical reaction but remains unchanged at the end of the reaction

Not destroyed by the reactions they catalyse Highly specific that is each enzyme can only catalyse one kind of

substrate Needed in small quantities because they are not used up but released

at the end of a reaction Enzyme-catalyses reaction are reversible Can be slowed down or completely stopped by inhibitors.

-e.g. : heavy metals such as lead and mercury Require helper molecules called cofactors Cofactors are divide by two:

a) organic cofactor like water soluble vitamin

b) Inorganic cofactor like ferum and copper

Naming of enzymesNaming of enzymes

An enzyme is named according to the name of the substrate it catalyses Other enzyme were named before a systematic way of naming enzyme was

formed

-e.g. : pepsin, trypsin and rennin

By adding suffix -ase at the end of the name of their substrate Enzyme for catalysing the hydrolysis Example :

substrate enzymes productslactose lactase glucose +

galactose

maltose maltase Glucose

cellulose cellulase Glucose

lipid lipase Glycerol + fatty acid

starch amylase Maltose

protein protease Pepton + polypeptide

The sites of enzyme synthesisThe sites of enzyme synthesis

Ribosomes are attached to the roughed endoplasmic reticulum. Information for the synthesis of enzyme is carried by DNA The different of bases in DNA are codes to make different protein RNA is formed to translate the codes into a sequence of amino acids Amino acids are bonded together to form specific enzyme according to the

DNA’s codes

Intracellular and extracellular Intracellular and extracellular enzymeenzyme

Intracellular : synthesised and retained in the cell for the use of cell itself

: found in the cytoplasm, nucleus, mitochondria and chloroplast Example : 1) oxydoreductase catalyse biological oxidation

2) reduction in the mitochondria

Extracellular : synthesised in the cell but secreted from the cell to work externally

Example : 1) digestive enzyme produced by the pancreas are not used by cells in the pancreas but are transported to the duodenum

Production of extracellular enzymesProduction of extracellular enzymes

• Protein/Enzymes are synthesized in the ribosomes are transported through the spaces between the rough endoplasmic reticulum

• Protein depart from the RER wrapped in vesicles that bud off from the sides of the RER

• These transport vesicles fuse with the membrane of the Golgi apparatus

• Secretory vesicles containing these modified protein bud off from the Golgi membrane and travel to the plasma membrane

• These vesicles will then fuse with the plasma membrane before releasing the proteins outside the cells as enzymes.

The mechanism of enzyme actionThe mechanism of enzyme action

• Enzymes are complex protein made of one or more polypeptide chains

• These polypeptide chain are folded into three-dimensional shape which include a pocket called an active site

• The ‘lock and key’ hypothesis

• The ‘substrate’ molecule represent the ‘key’

• The ‘enzyme’ molecule represent the ‘lock’

• The substrate molecule binds to the active site to form an enzyme-substrate complex

• The enzyme catalyses the substrate to form products, then leave the active site

• Enzyme molecule is now free to bind to more substrate molecules

Factor affecting enzyme activityFactor affecting enzyme activity

Temperature At low temperatures, an enzyme-catalysed reaction takes place slowly For every 10°C rise in temperature, the rate of reaction is doubled However, this is only true up to the optimum temperature Optimum temperature is the temperature at which an enzyme catalyses a

reaction at the maximum rate

Any increase in temperature will no longer increase the rate of reaction because the bonds that hold enzyme molecules together begin to break at high temperature, thus altering the three-dimensional shape eventually destroying active site

Enzymes lose their activities and are said to be denatured So, organisms cannot survive at temperatures above 40°C

Ph The optimum pH is the pH at which the rate of reaction is at the maximum A change in pH can alter the charges on the active sites of the enzyme and

the substrate surfaces,it can reduce the ability of both molecules to bind each other

Pepsin can function in an acidic condition (pH 2) within in the stomach Trypsin can function in alkaline condition (pH 8.5) within the duodenum

Substrate concentration Increase in substrate concentration, more substrate molecule are available

to bind the active sites of the enzyme Hence, more products will be produced Because more chances of collision between the substrate molecule and the

enzyme molecules for a catalytic reaction to take place In increase in substrate concentration will only speed up the reaction if there

are enough enzyme molecules to catalyse the additional substrate molecules

The rate of reaction is directly proportional to the substrate concentration until the reaction reaches a maximum rate

After maximum rate, all active site of the enzyme molecules are filled and engaged in catalysis

The enzyme is said to be saturated The concentration of enzyme becomes a limiting factor

Enzyme concentration When the concentration of an enzyme increases,more enzyme molecules

are available The rate of of reaction will increase only if there is abundant supply of

substrate molecules and other factors are constant because more active sites are made available for the catalytic reaction.

The rate of reaction is directly proportional to the concentration of the enzyme present until a maximum rate is achieved.

After the maximum rate,the doncentration of substrate becomes a limiting factor.

If the concentration of enzyme is doubled,the amount of substrate molecules also doubled.

• The uses of enzymes

• Can as catalysts in industries

• The use of enzyme in industrial processes is known as enzyme technology.

• Enzyme are use widely in our daily life

• be use

enzymes uses

protease Tenderise meat

amylase To convert starch to sugar in the making of syrup

lipase Ripening the cheese

In detergent

Effectively dissolve protein stain