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Enzymes

Enzymes. Enzymes are…. Proteins that act as catalysts (accelerate reactions) by creating a new reaction pathway Not specific for what they catalyze and do not permanently change during reactions. Function of Enzymes.

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Enzymes

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  1. Enzymes

  2. Enzymes are… • Proteins that act as catalysts (accelerate reactions) by creating a new reaction pathway • Not specific for what they catalyze and do not permanently change during reactions

  3. Function of Enzymes • Enzymes work by lowering the activation energy (the amount of energy needed to start a reaction).

  4. Check for Understanding With your partner, label the products, reactants, activation energy, progress of reaction, and free energy on the image below. Question: Using this image, what is one thing that the enzyme does in this reaction?

  5. Enzyme Enzyme-Substrate Complex • Substrate is the substance an enzyme acts on and is specific for each enzyme • Active site is the region of the enzyme that binds to the substrate Active Site Substrate

  6. S E E E Enzyme may be used again Enzyme-substrate complex P P Reaction coordinate Lock-and-Keys Model

  7. Lock-and-Keys Model • Keys = Substrates (multiple can bind to each enzyme) • Lock = Active Site on the Enzyme • As a result of the reaction, the products change shape • After the reaction is complete, the substrates are released, freeing up the enzymes to bind with more substrate

  8. Check for Understanding With your partner, using what we just discussed, fill in the boxes on the diagram below. Include the name of the part of the enzyme or substrate, and the events that are taking place for the boxes labeled #1-4.

  9. Substrate matching the enzyme approaches the active site Product Product The substrate bonds to the active site forming the enzyme-substrate complex The products formed are released and the enzyme is free to bind to a new substrate The enzyme speeds up the reaction, changing the shape of the substrate Active Site Enzyme

  10. Active Site substrate Enzyme induced fit Induced Fit • A change in the configuration of an enzyme’s active site (H+ and ionic bonds are involved). • Induced by the substrate.

  11. Factors that Impact Enzyme Function • Temperature • pH • Substrate Concentration • Inhibitors

  12. Denaturation Enzyme activity 10 0 20 30 40 50 Temperature / °C Temperature • Enzymes move faster as temperature increases • Above optimum temperature, the enzyme denatures – preventing it from binding with the substrate

  13. Enzyme activity Trypsin Pepsin 5 11 9 3 1 7 pH pH Optimum pH values • Extreme pH will result in denaturation • Enzyme structure changes • Substrate will no longer fit • pH levels different for different enzymes

  14. Substrate Concentration • More substrate causes the substrate to use up the available enzyme faster • Once all of the enzyme is bound, the reaction will slow and move at a constant state

  15. Enzyme Competitive Inhibitors • Chemicals that resemble an enzyme’s normal substrate and compete with it for the active site Substrate

  16. Noncompetitive Inhibitor Enzyme active site altered Noncompetitive Inhibitors • Chemicals that bind to part of the enzyme (not the active site), resulting in changing the shape of the active site  prevents the substrate from binding Substrate

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