Chemical Reactions and Enzymes

2 Chemical Reactions A process that changes or transforms one set of chemicals into another Mass and energy are conserved Reactants  Products 2 kinds: energy releasing (exothermic) and energy absorbing (endothermic)

Exothermic Reactions Reaction in which heat is given off (combustion of fuels) 3

Endothermic Reactions Reaction in which heat is absorbed (Ex. water is evaporated) 4

Activation Energy Energy needed to get a reaction going 5

Six Types of Chemical Reaction 1) Combustion: when oxygen combines with another compound to form water and carbon dioxide (exothermic) meaning they produce heat. C 8 H O 2 ---> 8 CO H 2 O (c) 2007 brainybetty.com ALL RIGHTS RESERVED. 6

2) Synthesis: when two or more simple compounds combine to form new one: A + B ---> AB One example: iron and oxygen to form iron (II) oxide: Fe + O ---> FeO (c) 2007 brainybetty.com ALL RIGHTS RESERVED. 7

3) Decomposition: a complex molecule breaks down to make simpler ones: AB ---> A + B One example: electrolysis of water to make oxygen and hydrogen gas: 2 H 2 O --- > 2 H 2 + O 2 (c) 2007 brainybetty.com ALL RIGHTS RESERVED. 8

4) Single displacement: This is when one element trades places with another element in a compound: A + BC ---> AC + B One example: magnesium replaces hydrogen in water to make magnesium hydroxide and hydrogen gas: Mg + 2 H 2 O ---> Mg(OH) 2 + H 2 (c) 2007 brainybetty.com ALL RIGHTS RESERVED. 9

5) Double displacement: when two different molecules switch places, forming two entirely different compounds: AB + CD ---> AD + CB One example: Pb(NO 3 ) KI ---> PbI KNO 3 (c) 2007 brainybetty.com ALL RIGHTS RESERVED. 10

6) Acid-base: The H + ion in the acid reacts with the OH - ion in the base, causing the formation of water and salt: HA + BOH ---> H 2 O + BA (salt) One example of an acid-base reaction is the reaction of hydrochloric acid (HCl) with sodium hydroxide: HCl + NaOH ---> NaCl + H 2 O Acid often = HF, HCl, HBr, etc. H (hydrogen in front of elements in group 7 or something with oxygen. Base often = OH at the end of the compound. LiOH, NaOH, KOH, Mg(OH)2, Ca(OH)2. (c) 2007 brainybetty.com ALL RIGHTS RESERVED. 11

Photosynthesis (c) 2007 brainybetty.com ALL RIGHTS RESERVED. 12

Enzymes Proteins that act as biological catalysts They speed up chemical reactions that take place in cells (catalysts) They are very specific and usually catalyze only one chemical reaction 13

Catalyst 14 A substance that speeds up the reaction by lowering activation energy

Substrates The reactants of enzyme-catalyzed reactions They bind to sites on the enzyme called active sites  Lock and Key CO 2 + H 2 O  H 2 CO 3 substrate 15

Regulation of Enzyme Activity Temperature, pH, and regulatory molecules can affect how well enzymes work Pepsin works best under acidic conditions (begins protein digestion) Some are regulated by molecules that carry chemical signals within cells that turn enzymes “on” or “off” 16