Year 12 Biology Macromolecules Unit Chapter 3 M10

Energy Flow M10. Enzymes increase reaction rates by lowering activation energy M10.1 Understand that reactions require an initial input of energy to proceed Enzymes are protein macromolecules Biological reactions would be very slow if they occurred at all without enzymes Chemical reactions involve the breaking of bonds and the reforming of bonds that hold atoms together in molecules. Reactant molecules must absorb energy break and this initial energy necessary to start the reaction is the –ACTIVATION ENERGY

Analogy- A good analogy is striking a match- the arm movement is the initial energy input as you strike the match-once the reaction starts( match burns)-it proceeds very rapidly-releases a considerable amount of free energy Activation energy is less when an enzyme is used.

M10.2 Describe how enzymes catalyse biological reactions by lowering the input of energy required to initiate the reaction. To refresh- enzyme substrate binding-the induced fit model –enzyme/substrate held by weak bonds One enzyme converts thousands of substrate molecules a second- Enzyme remains unchanged Binding may enable the substrate to be held in the correct orientation for the reaction to occur.

May be possible that the induced fit may stress the bonds in the substrate molecule and therefore lower the amount of energy to break bonds. Presence of an enzyme-reaction proceeds more easily and at reasonable temperatures as initial input of energy required to start reaction is much less