1.8 Factors Effecting Enzyme Action

Bee Brittain
Mind Map by , created about 3 years ago

AS - Level Biology (1 - Biological Molecules) Mind Map on 1.8 Factors Effecting Enzyme Action, created by Bee Brittain on 03/29/2016.

Bee Brittain
Created by Bee Brittain about 3 years ago
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1.8 Factors Effecting Enzyme Action
1 Temperature
1.1 A higher temperature means the substrate and enzyme molecules have more kinetic energy and move around more


  • The way this speeds up the reaction, is because the enzyme and substrate molecules come together to produce MORE enzyme-substrate complexes in a given time. Faster Rate of Reaction
1.2 There is an optimum temperature
1.2.1 Any temperature higher than the enzymes optimum will have enough energy to break the bonds that hold the enzyme in shape So therefore past the optimum, the enzyme becomes DENATURED It is no longer functional
2 pH
2.1 All enzymes have a maximum pH value
2.1.1 They also have a minimum
2.2 The pH of a solution is also a measure of its hydrogen ion concentration
2.3 Above and below the optimum (maximum) pH, the H+ ions and OH- Ions ound in acids and alkali's can mess up the ionic and hydrogen bonds holding the enzymes tertiary structure in place
2.3.1 So on either side of the optimum, the enzyme can be DENATURED!
2.4 A change in pH alters the charges on the amino acids that make up the active site of the enzyme.
2.4.1 As a result, the substrate can no longer attach to active site = NO ENZYME-SUBSTRATE COMPLEXES FORMED


  • The phrase "ENZYME-SUBSTRATE COMPLEXES" is in capitals because in your exam, that phrase, is key. In most enzyme questions there will be one mark just for that small phrase - easy marks!
3 Enzyme Concentration
3.1 Once an active site of an enzyme has acted on its substrate, it is free to repeat the procedure on another substrate molecule
3.2 More enzyme molecules in a solution
3.2.1 more likely substrate is to collide with one and form an ENZYME-SUBSTRATE COMPLEX therefore: Increasing the concentration of enzyme increases the rate of reaction
3.3 However, if the amount of substrate is limited
3.3.1 Increase in enzyme concentrate eventually has no further effect
4 Substrate Concentration
4.1 Higher the substrate concentration, the faster the reaction
4.1.1 this is because collisions become more likely and more active sites will be used More ENZYME-SUBSTRATE COMPLEXES
4.2 Saturation Point
4.2.1 All active sites are full/in use Substrate concentration makes no difference
4.3 Substrate conc. decreases with time during a reaction (unless more is added to reaction mixture)
4.3.1 If no other variables changed, rate of reaction will decrease over time too This means initial rate of reaction = highest rate of reaction