A simple view of life…. All living organisms are simply bags full of chemicals reacting together in a special order! The quicker these chemical reactions operate, the better the life in the bag of skin or membrane will operate! These chemical reactions that make up “life” are helped along by special chemicals called enzymes.

Enzymes 1.Are special protein molecules 2.Are found in all parts of all cells 3.Have an area called an active site 4.Names often end in: -ase

What enzymes do Enzymes are biological catalysts that: Speed up a reaction by lowering the activation energy (rate of reaction increases) Are not used up or changed during the reaction they speed up (they can be used over and over again) Each enzyme is specific to one reaction only (their active site will only fit certain substrate/reactant molecules)

How enzymes work There are 2 models of how enzymes work to catalyse a chemical reaction: 1.Lock and Key model 2.Induced Fit model Both models show a complex protein molecule with an active site. In both models the active site will only accept specific substrate (reactant) molecules.

Lock and Key Model Is the older of the 2 models on how enzymes work and is no longer accepted as fully correct, based on the latest scientific information.

Induced Fit Model Is currently accepted as the correct model for enzyme action.

Activation energy Chemical reactions usually need some energy to start them. This start up energy is called activation energy Enzymes lower the activation energy needed to help a chemical reaction occur and so speed up the reaction rate (RR). e.g. Peroxidase speeds up the reaction that changes the toxic substrate/reactant molecule of Hydrogen perioxide (H 2 O 2 ) into the safe products of water (H 2 O) and oxygen (O 2 ) inside liver and potato cells. Use the diagram models to show this reaction and label; Peroxidase / Enzyme molecule, Substrate /Reactant molecule (H 2 O 2 ), An Active Site, Product molecules (H 2 O and O 2).

What effects enzymes? pH (acid/ base). Enzymes often work best in a narrow pH range (optimum range) and a too acidic or basic environment can destroy them. Concentration (amount) of substrate (reactant) and/or enzyme molecules. More of either can speed the reaction rate up and less will slow down the RR. Temperature. Usually there is a narrow optimum range of temperature for most enzymes to work properly. Either too hot or too cold destroys or slows down the enzyme’s action. Enzyme molecules are destroyed (denatured) by extreme heat, because they are made from ?????

Co-factors and Co-enzymes, are extra chemicals that can help enzymes work. Other chemicals can destroy, damage or fill up (inhibitors) the active sites of enzymes e.g. the ions of the heavy metals, mercury and lead. Sketch and label a diagram of how an inhibitor can prevent an enzyme working properly.