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Enzymes

Enzymes. a special type of protein. What is an enzyme?. Enzymes are proteins which act as biological catalysts . Their subunits are amino acids. Enzymes are used by cells to trigger and control chemical reactions .

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Enzymes

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  1. Enzymes a special type of protein

  2. What is an enzyme? • Enzymes are proteins which act as biological catalysts. • Their subunits are amino acids. • Enzymes are used by cells to trigger and control chemical reactions. • Without enzymes, several reactions in cells would never occur or happen too slowly to be useful.

  3. What is a chemical reaction? • It is the process of changing one set of chemicals (reactants) into another set of chemicals (products) by rearranging the atoms. • Reactants’ bonds are broken and new ones are formed in the products. 2H2 + O2→ 2H2O

  4. What is a catalyst? • It is a substance that speeds up the rate of a chemical reaction. • It lowers the activation energy.

  5. What is activation energy? • Activation energy is the amount of energy needed to start a chemical reaction.

  6. Enzymes speed up chemical reactions by lowering their activation energy.

  7. What is a substrate? • Enzymes bind to molecules called substrates. • These substrates are the reactants that are catalyzed by the enzyme.

  8. Lock and Key Hypothesis • Each protein has a specific shape, therefore enzymes bind to substrates based on shape. • The site on the enzyme where the substrates bind is called the active site.

  9. Lock and Key Hypothesis • Enzymes bind to the substrates based on their complementary shape.. • The fit is so exact that the active site and substrates are compared to a “lock and key”.

  10. How are enzymes affected by the reactions? • Enzymes are NOT changed by the reactions they catalyze, therefore they are reusable!

  11. How can enzymes be affected? • Enzymes can be affected by temperature and pH. • Temperatures or pH outside the correct range can cause enzymes to break down or change shape. • This break down is called denaturation. • Therefore, enzymes in our body work best at 37°C (98.6°F) and at a pH between 6.5 to 7.5.

  12. How can enzymes be affected? Ex: Catalase is an enzyme that breaks down hydrogen peroxide. • H2O2 → H2O + O2 (gas) • A raw potato in H2O2 gives off O2. The boiled potato give no bubbles because the enzyme has changed due to heat.

  13. Induce Fit Hypothesis • Enzymes can change shape slightly to fit the substrate a little better (like a hand in glove).

  14. Enzymes can turn On & Off • Most cells contain proteins that turn enzymes on or off during critical stages of development.

  15. Enzymatic Reactions

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