Enzymes

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Lecture 4

• Enzymes

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Enzymes

• Proteins
• Catalyze all cellular reactions
• Enzymes are not changed by the reactions, and can
  be reused

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Protein Shape

• Proteins need the proper shape to function
• Increased temperature, high or low pH, or certain
  solvents, cause the bonds within the protein to
  be broken
• Denatured protein no longer functions

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Enzymes

• Function by lowering the activation energy of a
  chemical reaction so it is more likely to occur
• Enzymes weaken chemical bonds in the substrate

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Enzymes

• Very specific due to 3-D shape
• Contain an active site region where a specific
  substrate binds
• Substrate substance upon which an enzyme acts
• Enzyme Substrate ? Enzyme-Substrate
  complex
• Enzyme Product

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Cofactors and Coenzymes

• Some enzymes need help to build
• active site
• Cofactors inorganic molecules that help build
  active site of enzyme
• Coenzymes organic molecules that help build the
  active site

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Figure 5.3
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Enzymes

• Often Team Up in Metabolic Pathways
• A metabolic pathway is a sequence of chemical
  reactions

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Factors Influencing Enzymatic Activity

• Temperature chemical reaction increases as
  temperature increases, up to a certain point
• pH most enzymes has optimum pH
• Substrate concentration Increase substrate
  amount, increases reaction rate
• Inhibition

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Figure 5.5 - Overview
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Enzyme Inhibition

• Competitive Inhibition inhibitor competes with
  the substrate for the active site
• Non-Competitive inhibition when inhibitor and
  substrate act at different sites on the enzyme
• Feedback Inhibition inhibits an enzyme in the
  pathway so no product is available to feed the
  next reaction

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Figure 5.7 - Overview
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Figure 5.8
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Classification of Enzymes
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Classification- Based on where enzyme activity
occurs

• Exoenzymes
• Endoenzymes