Enzymes Notes PDF

ENZYMES BIOLOGICAL CATALYSTS! WHAT IS A CATALYST? A catalyst is a substance that speeds up the rate of a chemical reaction, without entering the reaction itself Catalysts can be: – Inorganic (heat) – Organic (enzymes) Most catalysts are organic! Am...

ENZYMES BIOLOGICAL CATALYSTS! WHAT IS A CATALYST? A catalyst is a substance that speeds up the rate of a chemical reaction, without entering the reaction itself Catalysts can be: – Inorganic (heat) – Organic (enzymes) Most catalysts are organic! Amoeba Sisters: Enzymes ENZYME FACTS! An enzyme is an organic catalyst made of protein Most enzymes end in –ase Enzymes work by lowering the activation energy of a chemical reaction. This means it lowers the amount of energy needed to start the reaction, so the reaction happens faster! HOW ENZYMES WORK Enzymes act on molecules called substrates They bind to their substrates at the active site Typically enzymes are larger than their substrates Enzymes fit into their substrates like a key fits into a lock: it is very specific! This is called the “lock and key model” of enzyme action  STEPS OF ENZYME ACTION 1. Enzyme joins with its substrate 2. Enzyme and substrate form an enzyme-substrate complex 3. Enzyme action takes place 4. Enzyme and products separate. The enzyme is unchanged and can be reused! INDUCED FIT MODEL Enzyme is not rigid and changes shape slightly when the substrate enters Still specific to one substrate! COENZYMES AND COFACTORS Enzyme helpers! Bind to enzyme and help it to better fit with its substrate Coenzymes: Organic (vitamins) Cofactors: Inorganic (metal ions like iron) FACTORS AFFECTING ENZYME ACTION Enzymes are picky! They only work under specific conditions Factors which affect enzyme action include – pH – Temperature – Concentration of enzymes and substrates PH AND ENZYME ACTION Each enzyme has a specific pH in which it will work Different enzymes work at different pH levels. – Pepsin, an enzyme in your stomach, works best at a pH of 2. Why? – Amylase, an enzyme found in your mouth, works best at a pH of 6.8. Why? TEMPERATURE AND ENZYME ACTION All enzymes have an optimal temperature at which they work the most effectively Optimal temperature for humans is 37°C Optimal temperature for dogs is 101-102°F WHAT HAPPENS IF TEMPERATURES GET TOO HIGH? Enzymes change shape (kind of like melting!) When this happens, we say the enzyme is denatured WHAT HAPPENS IF TEMPERATURES GET TOO HIGH? If the enzyme is not shaped correctly, it cannot bind with its substrate and can no longer do its job Changes in pH can denature enzymes too! DENATURED PROTEIN CONCENTRATION AND ENZYMES As concentration of both the enzyme and the substrate increases, the rate of enzyme action increases to a certain point, and then will level off WHY DOES THIS LEVELING OFF OCCUR? If the concentration of the enzyme increases, reaction rate will initially increase. However, as all of the substrate is broken down, the excess enzyme has nothing to combine with, so reaction rate levels off. If the concentration of the substrate increases, reaction rate will initially increase. However, if there are not enough enzymes to act on the increasing substrate, the reaction rate will level off.  SUMMARY QUESTIONS: 1. What type of biological molecule is an enzyme considered? 2. Why is enzyme action similar to the action of a key fitting into a lock? 3. What is the difference between a substrate and an active site? 4. Why are changes in pH and temperature critical to the proper functioning of an enzyme?