biology 12. enzymes are catalysts they speed up reactions
TRANSCRIPT
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