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Enzymes

Enzymes. Characteristics of Enzymes. Proteins Catalysts Speed up chemical reactions without being used up. How do they work?. Lower Activation Energy to speed up rates of reaction Reactions require energy to begin…enzymes lower the amount of energy required. Naming. Often end in “–ase”

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Enzymes

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  1. Enzymes

  2. Characteristics of Enzymes • Proteins • Catalysts • Speed up chemical reactions without being used up

  3. How do they work? • Lower Activation Energy to speed up rates of reaction • Reactions require energy to begin…enzymes lower the amount of energy required.

  4. Naming • Often end in “–ase” • The name usually relates to the reactants they are associated with or the reaction they help start

  5. A specific enzyme catalyzes each cellular reaction A unique 3-D shape of an enzyme determines which chemical reaction it catalyzes. Important Vocab: • SUBSTRATE: A specific reactant that an enzyme acts on is called a substrateof the enzyme. • ACTIVE SITE: A substrate fits into a region of the enzyme called an active site. • An active site is typically a pocket or groove on the surface of the enzyme.

  6. The enzyme and substrate form a complex… substrate Active site enzyme Enzyme-substrate complex

  7. Lock and Key Model + + E + S ES complex E + P P S S P

  8. The cellular environment affects enzyme activity. • An enzyme is most effective under certain conditions.

  9. Remember that proteins have a very specific structure • Primary through quaternary structure must be maintained for the protein to function properly • What happens if it is not?

  10. Structure • If an enzyme’s shape is changed so that it is no longer able to catalyze reactions, we call it… DENATURED • What kinds of things do you think could denature a protein?

  11. Denaturation Disruption of secondary, tertiary and quaternary protein structure by heat Break apart H bonds and disrupt hydrophobic attractions acids/ bases Break H bonds between polar R groups and ionic bonds heavy metal ions React with S-S bonds to form solids agitation Stretches chains until bonds break

  12. Applications of Denaturation • Hard boiling an egg • Wiping the skin with alcohol swab for injection • Cooking food to destroy E. coli. • Heat used to cauterize blood vessels • Autoclave sterilizes instruments • Milk is heated to make yogurt

  13. Think about it Tannic acid is used to form a scab on a burn. An egg becomes hard boiled when placed in hot water. What is similar about these two events?

  14. Solution Acid and heat cause a denaturation of protein. They both break bonds in the secondary and tertiary structure of protein.

  15. Temperature Temperature affects molecular motion • an enzyme’s optimal temperature produces the highest rate. -Most human enzymes work best at 35-40 ºC. WATCH OUT!!! If the temperature gets too high, the enzyme may be denatured!

  16. Factors Affecting Enzyme Action Optimum temperature Reaction Rate Low High Temperature

  17. Ions Salt concentration and pH influence enzyme activity. • SALT: The salt ions interfere with some of the chemical bonds that maintain protein structure. • pH: The same is true of the extra hydrogen ions at very low pH. -The optimal pH for most enzymes is near neutral. Where is the charged area on the following R groups?

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