Enzymes

• What are enzymes?


  Enzymes are biological catalysts that speed up chemical reactions in living organisms.
• What are the main components of enzyme structure?

  • Enzymes consist of proteins.
  • They may require cofactors for activity.
  • Examples of cofactors include NAD⁺ and FAD.
  • Haem groups are also examples of cofactors.
• What is the function of the active site in an enzyme?

  The active site is responsible for binding to a substrate and catalyzing a chemical reaction.
• How does the amino acid sequence affect the active site of an enzyme?

  The amino acid sequence determines the formation of the active site by specifying the amino acids involved in its formation.
• What types of interactions occur between the active site and the substrate?

  Amino acid side chains in the active site interact with the substrate through hydrogen bonds, ionic bonds, and van der Waals forces.
• Why is substrate specificity important in enzyme activity?

  Substrate specificity ensures that only the correct substrate is bound in the correct orientation, allowing the correct reaction to be catalyzed.
• What are the models of enzyme-substrate binding?

  • Lock and Key Model
  • Induced Fit Model
• What is enzyme inhibition?

  Enzyme inhibition is a process where the activity of an enzyme is reduced or stopped by a molecule that binds to it.
• What is the difference between reversible and irreversible inhibitors?

  Reversible inhibitors bind non-covalently and can be easily dissociated, while irreversible inhibitors form covalent bonds and permanently inactivate the enzyme.
• What are the three main types of reversible enzyme inhibition?

  1. Competitive inhibition
  2. Non-competitive inhibition
  3. Uncompetitive inhibition
• How does competitive inhibition work?

  In competitive inhibition, the inhibitor competes with the substrate for binding to the active site.
• What occurs during non-competitive inhibition?

  In non-competitive inhibition, the inhibitor binds to the enzyme regardless of whether the substrate is bound, reducing the enzyme's activity.
• What is uncompetitive inhibition?

  In uncompetitive inhibition, the inhibitor binds only after the substrate has already bound to the active site, preventing the reaction from occurring.
• What factors affect enzyme activity?

  • Temperature: Increases activity up to the optimum temperature, beyond which enzymes denature.
  • pH: Each enzyme has an optimum pH; extremes can denature the enzyme.
  • Non-covalent interactions: Affect enzyme-substrate complex formation.
  • Reversible and irreversible covalent interactions: Can alter enzyme activity permanently or temporarily.
• What happens to enzyme activity as temperature increases?

  Enzyme activity generally increases with temperature until it reaches the optimum temperature, after which the enzyme denatures.
• What is the optimum pH for enzymes?

  The optimum pH is the specific pH at which most enzymes function most efficiently.
• How do changes in pH affect enzyme activity?

  Changes in pH affect the charge on the amino acid side chains, altering the enzyme's shape and affecting the enzyme-substrate complex formation.
• What are irreversible covalent interactions in enzymes?

  Irreversible covalent interactions permanently alter enzyme activity by changing the enzyme's conformation or causing structural damage.
• What is the significance of disulphide bonds in enzymes?

  • Stabilize the tertiary or quaternary structure of an enzyme.
  • If broken or reduced, can lead to denaturation and loss of activity.
• What is the Michaelis-Menten plot?

  • A graphical representation of enzyme kinetics.
  • Shows the relationship between substrate concentration and reaction rate.
• What is the Lineweaver-Burk plot?


  • A linear transformation of the Michaelis-Menten plot.
  • Used to determine V_max and K_m.
• How do you calculate V_max from a Lineweaver-Burk plot?

  V_max is calculated as the reciprocal of the y-intercept.
• How do you calculate K_m from a Lineweaver-Burk plot?

  K_m is calculated as the negative reciprocal of the x-intercept.
• If K_m is -1/-0.5 mM, what is the value of K_m?

  K_m = 2 mM.
• If V_max is 1/0.25 min/µmol, what is the value of V_max?

  V_max = 4 µmol/min.
• How do competitive, non-competitive, and uncompetitive inhibition differ in terms of Lineweaver-Burk plots?

  • Competitive inhibition: Increases slope, same y-intercept.
  • Non-competitive inhibition: Same slope, increases y-intercept.
  • Uncompetitive inhibition: Decreases slope, increases y-intercept.
• What is the relationship between inhibition types and Lineweaver-Burk plots?

  • Competitive inhibition shifts the x-intercept.
  • Non-competitive inhibition shifts the y-intercept.
  • Uncompetitive inhibition affects both intercepts.