Lesson 2.4: Chemical Reactions & Enzymes

Chemical Reactions: A chemical reaction is a process that changes one set of chemicals into another by rearranging chemical bonds The elements you start with are reactants The elements you end with are products

Chemical Reactions: Exothermic Reaction- chemical reactions that release energy into surroundings; usually occur spontaneously Endothermic Reaction- chemical reactions that absorb energy from surroundings; usually require a source of energy

Chemical Reactions: The energy that is needed to get a reaction started is called the activation energy Activate = start

Chemical Reactions: Some chemical reactions are too slow or have activation energies that are too high to make them practical for living tissue Catalysts speed up reactions by lowering the activation energy

Enzymes: Enzymes are proteins that act as biological catalysts Enzymes speed up chemical reactions in cells

Enzyme- Substrate Complex: The reactants of enzyme-catalyzed reactions are known as substrates Enzymes break down substrates into the products

Enzyme- Substrate Complex: The substrates bind to a site on the enzyme called the active site The fit is so precise that the active site and substrates are often compared to a lock and key

Enzyme Activity: Temperature and pH can denature enzymes, preventing it from working Presence of other molecules can also affect enzymatic activity

Enzyme Examples: