Energy, Enzymes & Metabolism

Changing Matter The ability to move or change matter is called energy Energy exists in many forms Ex: Light & heat Energy can be converted from one form to another

Changing Matter Physical Change: When only form or shape of matter changes Chemical Change: When one substance changes into a different substance. Energy Laws: Conservation of Mass Conservation of Energy

Chemical Reactions Changing a substance requires a chemical reaction During this process Bonds between atoms are broken New bonds are formed A reactant is a substance that is changed in a chemical reaction A product is a new substance that is formed

Chemical Reactions Reactants Products Changes to or forms Reactants Products Example: When baking soda and vinegar are combined, they erupt as carbon dioxide gas is released NaHCO3 + CH3COOH CO2 + H2O + CH3COONa

Chemical Reactions Activation Energy: The minimum amount of energy required to start a chemical reaction Activation Energy

Chemical Reactions Endothermic Reactions absorb or use up heat Exothermic Reactions give off heat

Biological Reactions: Enzymes Living things carry out many chemical reactions that maintain homeostasis (stable internal environment) Many of these reactions would not occur without help…

Enzymes An enzyme is a catalyst A catalyst increases the speed and decreases the activation energy of biochemical reactions

Enzymes as Proteins Most enzymes are Proteins, which are made up of amino acids They are named for the substance they break down Ex: Sucrase is the enzyme that breaks down sucrose Ex: Amylase is the enzyme that breaks down amylose

Lock and Key Model Enzymes fit with reactants like a lock fits a key Each enzyme has an active site (key hole) where the reaction takes place Active site (key hole) determines which reactant/substrate (key) will fit. Each different enzyme acts only on specific substrates Enzymes are reusable! Substrate Active site Enzyme

How Enzymes Work: Step 1: Substrate binds to enzyme’s active site Chemical reaction is jumpstarted Step 3: Product is released

Controlling Enzyme Activity Temperature and pH level Proteins change shape as temperatures and pH levels change Because so much of an enzyme’s activity is based on its shape, these changes can stop an enzyme from working Inhibitors Can slow down or stop the activity of enzymes Ex: Snake venom; nerve gas

Metabolism Our cells get most of the energy needed for metabolism from the food we eat When food is digested, it is broken into small molecules that can enter the blood, which delivers them to the cells THIS INVOLVES MANY ENZYMES