WHAT IS AN ENZYME organic catalyst catlalyst assists

WHAT IS AN ENZYME? • organic catalyst – catlalyst - assists the reaction but remain unchanged when the reaction is over. Reusable • each chemical reaction requires one enzyme

• modify the rate of reactions • structure – large complex proteins consisting of one or more polypeptide chains whose names end in –ase – substrate – substance worked on by enzyme

ENZYME maltase lipase protease amylase SUBSTRATE maltose lipids proteins amylose

• protein nature – either all protein or proteinc with non-protein parts, called coenzymes – also known as VITAMINS • active site – formation of pockets into which reacting molecules fit

HOW DO ENZYMES WORK? • 2 MODELS OF ENZYME FUNCTION – ENZYME-SUBSTRATE COMPLEX – “LOCK AND KEY” MODEL

ENZYME SUBSTRATE COMPLEX • enzyme forms a temporary association with a substance whose reaction rate is affected • close physical association between enzyme and substrate is formed enzyme-substrate complex

• enzyme action takes place in enzymesubstrate complex • upon completion of reaction, enzyme and product(s) separate, enzyme is available for another reaction

LOCK AND KEY MODEL • particular enzyme will usually only form a complex with one particular type of substrate

WHAT INFLUENCES ENZYMES? • TEMPERATURE • AMOUNT OF ENZYME & SUBSTRATE • p. H

TEMPERATURE • reaction rate increases until an optimum temperature • enzyme action rate decreases • At high temperatures, enzymes denature

AMOUNT OF ENZYME & SUBSTRATE • when an excess of substrate is added, the rate of enzyme action increases to a point then remains fixed as long as the enzyme concentration remains constant

p. H • enzymes work best at different p. H ranges

• **a p. H of 7 provides the optimum environment** – acids - high H+ concentration which means LOW p. H – below 7 – bases – low H+ concentration which means HIGH p. H – above 7