Enzymes Most chemical reactions require energy to get started, called Activation Energy. Some reactions require a large amount of energy, some less Cells would be harmed if they contained all of the activation energy for every chemical reaction Catalysts called enzymes are used to solve this problem A protein that speeds up the rate of a reaction by lowering the activation energy.

Enzymes Any reactant of an enzyme reaction is called a Substrate The area of the enzyme that the substrate attaches to is called the active site An enzyme can ONLY work with 1 type of substrate Ex: Enzyme “sucrase” only works with sucrose Most enzymes have an “ase” ending To get more products from a reaction, more substrate can be added to an enzyme More products until a certain point is reached Only a certain number of enzymes in cells that can be working at 1 time

Sucrose Glucose + Fructose Enzymes “Lock and Key” Model: Substrates and active site are a ‘perfect’ fit like a key and lock. Only 1 type of enzyme with 1 type of substrate Enzymes are NOT changed or used up in a reaction and can be used again Sucrose Glucose + Fructose

Factors That Impact Enzymes The shape of the active site can change, then the substrate cannot attach and the chemical reaction cannot happen, this is called denaturing Temperature: All enzymes have a certain temperature they work best in; changing it denatures the enzyme pH: All enzymes have a certain pH they work best in; changing it denatures the enzyme Siamese cats have an enzyme that produces dark pigments. Enzyme gets denatured in the “warmer” areas of its body, and is active at cooler areas Enzymes that break down starch in your mouth (pH 7) will not work in your stomach (pH 2)