1.4 Biological reactions are regulated by enzymes

• What type of proteins are enzymes?


  Globular proteins
• What is the structure of enzymes?

  They have a tertiary structure
• Where are enzymes synthesized?

  By living cells
• What are intercellular enzymes?

  Enzymes that act inside the cell
• What are extracellular enzymes?

  Enzymes secreted by cells
• What is the active site of an enzyme?

  A 3D space for substrate binding
• How does the 3D shape of an enzyme affect its function?

  It determines the shape of the active site
• What happens if the sequence of amino acids in an enzyme changes?

  The active site will change shape
• Why is the complementarity of the active site and substrate important?

  It allows the substrate to bind effectively
• What does the diagram of an enzyme illustrate?

  • Space-filler model of an enzyme
  • Blue area shows the active site
  • Substrates are indicated in the model
• What do enzymes do when a substrate and enzyme collide successfully?

  They form an enzyme-substrate complex
• How does a substrate bind to an enzyme?

  By interactions with R groups of amino acids
• What factors affect the ability of R groups and substrates to form bonds?

  Temperature and pH
• What happens to the bonds in the substrate during the enzyme-substrate reaction?

  They are distorted, putting strain on them
• What is the effect of bond distortion in the substrate?

  It increases the chance that bonds will break
• What occurs after the bonds in the substrate break?

  New atoms come closer together to form new bonds
• What is required to break existing bonds in a substrate?

  Energy is needed to break the bonds
• What happens when new bonds are formed in the reaction?

  Energy is released when new bonds are made
• What is the term for the energy needed for a reaction to take place?

  Activation energy
• How does an enzyme affect the activation energy of a reaction?

  It reduces the activation energy needed
• What role does an enzyme play in a chemical reaction?

  It acts as a biological catalyst
• What happens to the enzyme during the reaction?

  The enzyme is unchanged during the reaction
• What is the process of enzyme action summarized as?

  1. Substrate binds to active site
  2. Bonds in substrate are distorted
  3. Bonds break, new atoms come together
  4. New bonds form, releasing energy
  5. Activation energy is reduced
  6. Enzyme remains unchanged
• It is important to remember that each enzyme is specific to a particular substrate – so even if three substrates undergo the same reaction, there has to be three different enzymes to carry out this same function.

  For example, the reactions shown below both remove two hydrogen atoms from a substrate molecule, but because the substrate molecules are different they cannot fit into the same active site as different bonds will form – so different dehydrogenase enzymes are needed.

  
• What is the lock and key hypothesis in enzyme action?

  The active site is like a lock for substrates
• Why must the substrate be complementary to the active site?

  To ensure proper binding and reaction
• What is the lock and key hypothesis in enzyme action?

  The active site is like a lock for substrates
• Why must the substrate be complementary to the active site?

  To ensure proper binding and reaction
• What must happen for bonds to form in the enzyme-substrate complex?

  The substrate must collide in the correct orientation
• What must happen for bonds to form in the enzyme-substrate complex?

  The substrate must collide in the correct orientation
• What occurs while the substrate binds to the enzyme?

  Chemical changes take place in the substrate
• What occurs while the substrate binds to the enzyme?

  Chemical changes take place in the substrate
• What happens to the enzyme after the reaction?

  The enzyme is not affected and can be reused
• What is catabolism in the context of enzyme action?

  Breaking down complex substrates into products
• What happens to the enzyme after the reaction?

  The enzyme can be reused
• What are the key differences between anabolism and catabolism in enzyme action?

  • Anabolism:
  • Combines substrates
  • Forms larger molecules
  • Catabolism:
  • Breaks down substrates
  • Produces smaller molecules
• What is catabolism in the context of enzyme action?

  Breaking down complex substrates into products
• What type of enzymes are involved in catabolic reactions?

  Digestive enzymes
• What are the key features of the lock and key hypothesis?

  • Active site is a fixed shape
  • Substrate must fit like a key
  • Correct orientation needed for binding
  • Enzyme remains unchanged after reaction
• What are the differences between anabolism and catabolism?

  Anabolism:

  • Combines substrates
  • Forms larger molecules

  
  

  Catabolism:

  • Breaks down substrates
  • Produces smaller molecules