Chemical Reactions & Enzymes

• Chemical Reactions & Enzymes

  • A chemical reaction is a process that changes one set of chemicals into another set of chemicals
  • Reactants: the compounds that go INTO a reaction
  • Products: the compounds that are formed
  • Ex. Cellular Respiration is a chemical reaction
  • Every organism must have a source of energy to carry out chemical reactions that keep them alive
  • Ex. Plants get their energy from the sun & animals eat plants or other animals

  
• Energy in Reactions

  • energy is released or absorbed whenever chemical bonds form or are broken as in digestion
  • Some reactions need energy to get the reaction started like getting a ball rolling.
  • This energy is called the activation energy
• Enzymes - Pt. 1

  • Catalysts are chemicals that speed up reaction
  • Enzymes are proteins that are biological catalysts in living organisms
  • Enzymes speed up chemical reactions by lowering the activation energy (the energy needed to start the reaction)
• Enzymes - Pt. 2

  • Enzymes work through the Enzyme-Substrate Complex
  • The specific shape of an enzyme (protein) allows reactants (called substrates) to bond together or break apart and make a product more quickly
  • The complex is like a "lock and key" (one key fits one lock)
  • "Active site" is the place on an enzyme where the substrate fits with the enzyme
  • The reaction occurs when the enzyme and substrate are bound together
  • The products are released
  • The enzyme is free to be reused with more substrate molecules.

  
• Regulation of Enzyme Activity

  • pH: Enzymes work best in certain pH ranges/
  • ex: lipase range 7-9, best pH=8
  • Temperature: Extreme temperature affect enzyme activity
  • When an enzyme can no longer work it is denatured
  • When an enzyme is denatured, the polypeptide strand unwinds and therefore the enzyme has a different shape
  • It can no longer bind to its substrate and allow a reaction