Chemical Reactions

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Chemical Reactions Enzymes

• pp. 49-53

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Chemical Reactions

• Occur when chemical bonds are formed, rearranged,
  or broken
• Absorb or release energy
• A chemical equation is like a sentence describing
  what happens
• It must be balanced!
• Examples
• A B ? AB CO2 H2O ? H2CO3
• CD ? C D H2CO3 ? CO2 H2O
• EF G ? EG F

3
Real Examples

• Amino acid amino acid ? protein
• Glycogen ? glucose glucose glucose
• C6H12O6 6O2 ? 6CO2 6H2O
• NaHCO3 HC2H3O2 ? NaC2H3O2 H2O CO2
• Reactants ? Products

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Why do Chemical Reactions Occur?

• All particles are in constant motion due to
  kinetic energy Animation
• In a solid, particles vibrate
• In a liquid, particles collide
• Several factors affect how fast chemical
  reactions happen
• Temperature
• Concentration
• Particle size
• Enzymes (catalysts)

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What are Enzymes?

• Enzymes speed up the chemical reactions that take
  place in cells
• All enzymes are proteins
• Proteins are chains of amino acids
• Enzyme names usually end in -ase
• Ex catalase
• 2H2O2 ? 2H2O O2

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How do Enzymes Work?

• Enzymes provide a site (the active site) where
  reactants come together
• Specific fit like a lock and key determined by 3D
  shape
• Reduce the activation energy needed to start the
  reaction
• Enzyme is unchanged after the reaction

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Animations Lactase lactose Revisit collisions
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Denatured Proteins

• The complex 3D shape of proteins (including
  enzymes) is changed by
• Extreme pH
• Extreme temperature
• If changed, the protein is denatured
• The active site of a denatured enzyme will no
  longer fit the substrate reactants), so it wont
  work properly

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Metabolism

• All of the chemical reactions in the body
  together make up metabolism!

10
Jello Demo
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Review

• Which side of a chemical reaction are the
  products on? The reactants?
• Do chemical reactions happen faster in solids or
  liquids?
• What are the 4 factors influencing the rate of
  chemical reactions?
• All enzymes are _____, which are chains of _____
  _____.
• Enzyme names end in -___.
• What makes enzymes so specific?
• What are the 2 factors that can denature a
  protein?