Biology Topic 3: Enzymes

• Optimal Temperatures:

  • Chemical reactions in the body speed up with increasing internal body temperature.
  • Molecules gain kinetic energy at higher temperatures, increasing collision frequency.
  • Enzyme-catalyzed reactions follow the same pattern.
  • Each enzyme has an optimal temperature range; human body enzymes function best at 37°C.
  • Beyond the optimal range, enzymes may denature, losing their function irreversibly.
• pH and Enzyme Activity:

  • Enzymes have optimal pH ranges for activity.
  • Extreme pH levels can denature enzymes, disrupting their function.
  • Enzyme activity versus pH graph forms a bell-shaped curve due to denaturation at extremes.
  • Different enzymes have varying optimal pH ranges.
• Enzyme and Substrate Concentration:

  • Increasing substrate concentration while keeping enzyme concentration constant increases reaction rate.
  • Analogy: More reactants (substrates) lead to faster reactions.
  • Relationship demonstrated through a graph.

  
• Competitive and Non-competitive Inhibition:

  • Competitive Inhibition: Inhibitor binds to the active site, blocking substrate binding.
  • Non-competitive Inhibition: Inhibitor binds to an allosteric site, causing a conformational change in the active site.
  • Both types can be reversible or irreversible.
• Reversible Inhibition:

  • Weaker bonds between enzyme and inhibitor allow for reversibility.
  • Competitive reversible inhibitors can be overcome by increasing substrate concentration.
  • Non-competitive reversible inhibitors are not influenced by substrate concentration.

  Irreversible Inhibition:

  • Strong, unbreakable bonds between enzyme and inhibitor.
  • Irreversible inhibitors often occupy the active site.
  • Irreversible inhibition leads to a permanent loss of enzyme function.
• Enzyme Inhibitors in Biochemical Pathways:

  • Inhibitors regulate biochemical pathways.
  • Inhibition can prevent overproduction of products.
  • Example: Self-regulating pathway where one enzyme inhibits another to control product levels.
• Cofactors and Coenzymes:

  • Some enzymes require assistance from cofactors.
  • Coenzymes, a subset of cofactors, are organic molecules.
  • Coenzyme cycling involves structural changes in coenzymes during reactions.
• Adenosine Triphosphate (ATP):

  • ATP is a crucial coenzyme for energy transfer in cells.
  • It undergoes phosphorylation (adding phosphate) and dephosphorylation (removing phosphate) reactions.
  • ATP can cycle between loaded (ATP) and unloaded (ADP) forms.
• Activation energy is the energy required for a chemical reaction to occur. It is the difference of the maximum amount of energy minus the energy of the reactants on a energy graph.
• Enzymes are a type of protein that speed up (catalyse) chemical reactions inside cells.

  They are very specific. The active site on the enzyme has a complementary shape to the reactant/s (substrate).

  They remain unchanged when they catalyse a reaction and can be reused many times.
• Lock and Key: the active sites is exactly complementary to the substrate that it acts upon, like a key fitting into a lock.
• Induced fit: the more accurate model of enzyme function. The active site has a somewhat complementary shape but does not perfectly match until it binds with the substrate.
• Denaturing

  Remember shape = function

  Certain conditions can disrupt the bonds within the enzyme and change it’s 3-dimensional shape

  This will change the shape of the active site meaning the substrate can no longer bind and the enzyme is non-functional.