Biology 3A

Enzymes are catalysts They speed up reactions

Enzyme terminology Active site – Substrate – Product – Enzyme-substrate complex –

Enzyme terminology Active site – where the substrate attaches Substrate – what enters the reaction Product – the result of the reaction Enzyme-substrate complex – substrate attached to enzyme

Enzymes are specific Each enzyme has an active site the correct shape to attach to one particular substrate

Enzymes are not used up in a reaction Substrates are turned into products, then the enzyme releases the product and is free to attach to a new substrate

How enzymes work – the lock and key model

How enzymes work – the lock and key model Substrate fits into active site perfectly – like a key into a lock Enzymes are specific because their active sites are exactly the right shape for only 1 particular substrate

How enzymes work – the induced fit model

How enzymes work – the induced fit model Substrate fits into active site but, not perfectly – this puts strain on the substrate, helping reduce the activation energy needed to convert it into product Enzymes are specific because their active sites are approximately the right shape for that particular substrate

Enzymes are proteins They are made of long strands of amino acids. The strands coil due to bonds between the side chains of different amino acids The coiling causes pockets that provide active sites for the attachment of substrate Because they are proteins they are effected by anything that can damage or change protein structure

Factors affecting enzyme action 1 Temperature Enzyme activity Temperature

Factors affecting enzyme action 1 Temperature Enzyme activity As temperature increases, activity increases due to increased movement of molecules Above a certain temperature, activity decreases as enzyme destroyed (denatured) by the heat Temperature

Factors affecting enzyme action 2 pH Acid Neutral Base Enzyme activity pH

Factors affecting enzyme action 2 pH Acid Neutral Base Enzyme activity pH Enzymes are pH specific – they only work at certain pH As pH changes, their shapes change, so they no longer have a useable active site

Factors affecting enzyme action 3 Substrate concentration Enzyme activity Substrate concentration

Factors affecting enzyme action 3 Substrate concentration Enzyme activity Substrate concentration As substrate concentration increases, so does enzyme activity up to a maximum level This is due to the increased chance of enzyme and substrate bumping into each other The maximum limit is set by other factors eg the amount of enzyme present

Factors affecting enzyme action 4 Product concentration Enzyme activity Product concentration

Factors affecting enzyme action 4 Product concentration Enzyme activity Product concentration As product concentration increases, so enzyme activity decreases This is due to the decreased chance of enzyme and substrate bumping into each other

Factors affecting enzyme action 5 Enzyme concentration Enzyme activity Enzyme concentration

Factors affecting enzyme action 5 Enzyme concentration Enzyme activity Enzyme concentration As enzyme concentration increases, so does enzyme activity up to a maximum level This is due to the increased chance of enzyme and substrate bumping into each other The maximum limit is set by other factors eg the amount of substrate present

Factors affecting enzyme action 6 Presence of cofactors Enzyme activity Cofactor concentration

Factors affecting enzyme action 6 Presence of cofactors Enzyme activity Cofactor concentration As cofactor concentration increases, so does enzyme activity up to a maximum level This is due to the increased effectiveness of the enzyme In some cases the enzyme will not work without the cofactor The maximum limit is set by other factors eg the amount of substrate present

Factors affecting enzyme action 7 Presence of inhibitors Enzyme activity Inhibitor concentration

Factors affecting enzyme action 7 Presence of inhibitors Enzyme activity Inhibitor concentration As inhibitor concentration increases, so enzyme activity decreases This is due to the enzymes being de-activated by the inhibitor