Enzymes

• What type of protein are enzymes?

  Globular proteins
• What structure do enzymes have?

  Specific tertiary structure
• Why are enzymes specific for one reaction only?

  Active site has a specific shape
• How is a substrate held onto the enzyme?

  Weak non-covalent interactions
• What 3 conditions must be met for a chemical reaction to take place?

  1. Reactant molecules must collide with sufficient energy
  2. Energy of products must be lower than reactants
  3. Activation energy must be supplied
• How do enzymes lower activation energy?

  1. Putting stress on the bonds within a molecule
  2. Holding molecules closer together
• Enzymes act by lowering activation energy of chemical reactions.
• Why does rate of reaction increase as substrate concentration increases?

  Chance of successful collision increases
• Enzymes lower activation energy by forming enzyme substrate complexes
• The enzyme substrate complex can be formed because the shape of the active site and substrate are complementary to each other.
• How does the induced fit model differ to the lock and key model?

  1. Active site changes to an inactive shape after reaction
  2. Induced fit model suggests that enzymes structure is flexible
• Temperature affecting enzyme action

  
• Enzyme denaturing is when temperature or pH alters the tertiary structure of the enzymes active site by breaking hydrogen or ionic bonds between the amino acids.
• pH and it's affect on enzymes

  
• Substrate concentration and the affect on enzymes

  A - more substrate molecules present, greater chance of collisions with enzyme. More enzyme-substrate complexes are formed, increased rate of reaction

  B - Increasing substrate concentration has no effect on reaction rate as all the enzymes active sites are occupied.

  
• Enzyme concentration and the effect on enzymes

  A - More enzymes means more active sites, more enzyme-substrate complexes formed. Rate of reaction increased, limiting factor is enzyme concentration.

  B - All substrate molecules have been used up to form enzyme-substrate complexes. Limiting factor is substrate concentration.

  
• Enzyme inhibitors are molecules that directly or indirectly bind to the active site of an enzyme and prevent the substrate from binding.
• Competitive inhibitors bind directly to the active site of an enzyme and prevent substrate binding.

  
• Non competitive inhibitors bind to the allosteric site and prevent the active from changing shape to fit substrate.

  
• Metabolic pathway - series of reactions in which each step is catalysed by an enzyme.