Chemical Reactions

All the chemical reactions in our bodies are called metabolism. Breakdown and reassemble molecules in the body. Chemical bonds are broken and formed during chemical reactions.

CH 4 + 2O 2  CO 2 + 2H 2 O REACTANTS PRODUCTS YIELDS (methane) + (oxygen)  (carbon dioxide) + (water)

Coefficients = # of molecules of a compound  Ex: 6O 2 = 6 molecules of Oxygen (O)  3H 2 O = 3 molecules of H 2 O CH 4 + 2O 2  CO 2 + 2H 2 O

Subscripts = # of atoms of an element  Ex: CH 4 = 1 atom C, 4 atoms H  CO 2 = 1 atom of C, 2 atoms O CH 4 + 2O 2  CO 2 + 2H 2 O

How many atoms of O are in 6O 2 ? 12 atoms of O!

In ALL chemical equations the same number of atoms of elements are on the reactant and the product side of chemical equations o Why?  Because of the Law of Conservation of Matter (atoms are never created or destroyed; they are simply rearranged!)

o We balance equations so the Law of Conservation of Mater is NOT violated! o We must always balance equations using coefficients!!

o Subscripts can never be changed! o Coefficients must always be placed in FRONT of the entire compound! o Create an atom inventory

H 2 + O 2  H 2 O

CaO + KBr  K 2 O + CaBr 2

Al 2 S 3 + BaCl 2  AlCl 3 + BaS

The key to a chemical reaction is energy! Most compounds in living things cannot undergo chemical reactions without energy

Activation energy = the minimum amount of energy needed for reactants to form products in a chemical reaction o Look at Graph A: the peak in the graph represents the amount of energy that must be added to the system to make the reaction occur! Graph A

All living things are chemical factories driven by chemical reactions! Enzymes (catalysts) need to be present in order to reduce the activation energy and allow the reaction to proceed quickly.

Look at Graph B: the enzyme lowers the activation energy and the product will be formed sooner! Graph B

Catalyst = a substance that lowers the activation energy needed to start a chemical reaction. Enzyme = special proteins that are biological catalysts that speed up the rate of a chemical reaction  Essential to life!  Specific to one reaction

How do ENZYMES Work? The reactants that bind to the enzyme are called substrates. The specific location where a substrate binds on an enzyme is called the active site.

How do ENZYMES Work? The active site and substrate have complementary shapes (lock-and- key). o Enzymes are very specific for the substrates that will change!

How do ENZYMES Work? When the enzyme-substrate complex forms, chemical bonds are broken and new bonds form to produce the products. Enzyme releases the product and the enzyme can be used again

Factors That Affect Enzymes: 1) pH (how acidic or basic a substance is) 2) Temperature most enzymes in human cells are most active at 98.6  F pH & temperature will denature (change the shape) of the enzyme so it will not be able to bond with the corresponding substrate!

Examples Of Enzymes Working: Helps with digestion DNA replication Enzymes in the venom of a venomous snake break down the membranes of a person’s red blood cells

Examples Of Enzymes Working: Hard green apples ripen because of the action of enzymes Photosynthesis and cellular respiration provide energy for the cell with the help of enzymes

pH = how acidic or basic a substance is Acid = substance that forms H + (hydrogen ions) in water HCl  H + + Cl - (pH LESS than 7) Water

Base = substance that forms OH - (hydroxide ions) in water NaOH  Na + + OH - (pH MORE than 7) Water

0714 BASE ACID N E U T R A L