Biology 12

Enzymes are catalysts

They speed up reactions

How enzymes work – the lock and key model

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

Enzyme terminologyActive site – where the substrate attachesSubstrate – what enters the reactionProduct – the result of the reaction Enzyme-substrate complex – substrate

attached to enzyme

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 acidsThe coiling causes pockets that provide active sites for the attachment of substrateBecause they are proteins they are effected by anything that can damage or change protein structure

Pineapple experiment 1

• Hypothesis• Independent variable• Dependent variable• Control• Controlled variables

Water Fresh pineapple Tinned pineapple Boiled pineapple

Heating or processing pineapple juice will damage the enzymes it contains

Type of pineapple juice

Whether the gelatine sets

Test tube with water

Same size test tubes, same amount of gelatine, same temperature, same volume of liquid added

Pineapple experiment 2

• Hypothesis• Independent variable• Dependent variable• Control• Controlled variables

Acid Neutral Base

Same size test tubes, same amount of gelatine, same temperature, same volume of liquid added

Whether the gelatine sets

Acidity will affect enzyme activity

The acidity

The acid test tube – original pH of pineapple juice

Factors affecting enzyme action 1Temperature

Enzyme activity

Temperature

As temperature increases, activity increases due to increased movement of moleculesAbove a certain temperature, activity decreases as enzyme destroyed (denatured) by the heat

Factors affecting enzyme action 2

pH Acid Neutral Base

pH

Enzyme activity

Enzymes are pH specific – they only work at certain pHAs 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

As substrate concentration increases, so does enzyme activity up to a maximum levelThis is due to the increased chance of enzyme and substrate bumping into each otherThe maximum limit is set by other factors eg the amount of enzyme present

Factors affecting enzyme action 4

Product concentration Enzyme activity

Product concentration

As product concentration increases, so enzyme activity decreasesThis is due to the decreased chance of enzyme and substrate bumping into each other

Factors affecting enzyme action 5

Enzyme concentrationEnzyme activity

Enzyme concentration

As enzyme concentration increases, so does enzyme activity up to a maximum levelThis is due to the increased chance of enzyme and substrate bumping into each otherThe 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

As cofactor concentration increases, so does enzyme activity up to a maximum levelThis is due to the increased effectiveness of the enzymeIn some cases the enzyme will not work without the cofactorThe maximum limit is set by other factors eg the amount of substrate present

Factors affecting enzyme action 7

Presence of inhibitorsEnzyme activity

Inhibitor concentration

As inhibitor concentration increases, so enzyme activity decreasesThis is due to the enzymes being de-activated by the inhibitor