A] ENZYMES

• Catalysts - substance that speeds up a reaction without being changed in the process.
• Substrate - a substance that an enzyme acts on
• Enzyme - a protein that serves as a biological catalyst, changing the rate of a chemical reaction without itself being changed into a different molecule in the process
• End products - the chemicals that result from an enzyme assisted reaction
•                                          catalase
• Formula: 2H₂O₂ -----------------> 2 H₂O + O₂
• the substrate that we study in this lab is hydrogen peroxide
• the enzyme that we study in this lab is catalase
• the end products are water and oxygen
• Oxygen gas comes off as bubbles
• the rate of this bubbling indicates the rate of reaction
• Source of the catalase - beef liver that has been thoroughly blended
• blending breaks open the cells to release the enzyme
• blended up liver is called the “homogenate”
• Enzymes
• highly specific (i.e. a particular enzyme only interacts with a certain substrate)
• specificity comes from the complex tertiary or quaternary structure of  proteins
• this structure comes from the primary sequence of amino acids built from a genetic code (DNA)

B] EFFECT OF ENZYME CONCENTRATION

• Only the concentration of the enzyme varies - the total volume, the pH, and the temperature are the same in all the tubes
• As the concentration of enzyme increases, the rate of enzyme reaction increases

C] EFFECT OF TEMPERATURE

• Only the temperature of the enzyme and peroxide varies
• ice bath (freezing point of water) = 0^o C
• room temperature = approx. 22^o C
• human body temperature = 37^o C
• boiling water = 100^o C
• Enzymes work best at the temperatures they are designed for
• catalase normally occurs at cow’s body temperature and thus works best at this temperature
• at high temperatures, enzymes denature - they lose their three dimensional shape and lose their ability to function (a permanent change)

D] EFFECT OF pH

• The acidic or basic strength of a solution may be expressed in terms of a number called the pH of that solution
• the pH scale expresses the concentration of hydrogen ions
• the pH scale ranges from 0 to 14
• acids have a pH below 7 (the more concentrated the acid, the lower the pH value)
• distilled water is neutral and has a pH of 7
• bases have a pH above 7 (the more concentrated the base, the higher the pH value)
• We use hydrochloric acid to make our solutions acidic and sodium hydroxide to make our solutions basic
• Enzymes work best at the pH’s they are designed to work in
• catalase works best at a pH near 7
• catalase functions in the interior of cow liver cells
• the pH of the interior of most cells (including liver cells) is maintained around 7