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

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

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 vitaminb) Inorganic cofactor like ferum and copper

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

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 : 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

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.

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

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