Enzymes

• Enzyme-substrate complex is formed when the substrate binds to an enzyme.
• After the product has been released from the active site, the enzyme can be used again to catalyze another reaction.
• Enzyme-substrate complex is formed when the substrate binds to an active site on the enzyme.
• When the substrate enters the active site, it undergoes chemical changes to form products.
• The active site of an enzyme has a specific shape that fits only one type of molecule, called the substrate.
• After catalysis occurs, the product leaves the active site and the enzyme returns to its original form.
• When the substrate enters the active site, it undergoes chemical change (catalysis).
• The active site of an enzyme has a specific shape that fits only one type of molecule, called its substrate.
• Temperature affects the activity of enzymes by altering their shape and function.
• The rate of an enzymatic reaction depends on several factors such as temperature, pH, concentration of reactants, presence of inhibitors or activators, and availability of cofactors.
• Most enzymes have an optimal temperature range where they are most active.
• The enzyme-substrate complex undergoes chemical changes that result in the formation of products.
• Enzymes


  Biological catalysts made of proteins
• Enzymes


  • They speed up chemical reactions
  • They remain chemically unchanged at the end of the reaction
• Characteristics of enzymes


  • They are biological catalysts made of proteins
  • They speed up chemical reactions
  • They remain chemically unchanged at the end of the reaction
  • They are required in small amounts
  • They can catalyse reversible reactions
  • They are highly specific in action due to their specific 3-D shape which contains an active site
  • They are affected by changes in temperature and pH
• Lock-and-key hypothesis


  • Explains enzyme specificity
  • An enzyme has a specific 3-D shape which contains an active site
  • Only the substrate with a 3-D shape complementary to the active site can bind to the enzyme
  • The substrate acts like a key while the enzyme acts like a lock
• Enzyme catalysis


  1. Substrate binds to active site of enzyme

  2. Enzyme-substrate complex forms

  3. Chemical reaction occurs and substrate is converted to products

  4. Products detach from active site

  5. Enzyme remains chemically unchanged
• Enzyme-catalysed reactions


  • Amylase digests starch to maltose
  • Maltase digests maltose to glucose
  • Protease digests proteins to amino acids
  • Lipase digests fats to fatty acids and glycerol
• As temperature increases


  Rate of enzyme-catalysed reaction increases
• At optimum temperature


  Rate of enzyme-catalysed reaction is highest
• Beyond optimum temperature


  Rate of enzyme-catalysed reaction decreases drastically as enzymes become denatured
• As pH changes


  Rate of enzyme-catalysed reaction changes
• Different enzymes have different optimum pH
• Extreme changes in pH lead to enzyme denaturation
• Enzymes


  Affected by temperature
• As temperature increases


  The rate of enzyme reaction increases
• Enzyme at low temperatures


  • Less active
  • Kinetic energy of molecules is low
  • Enzyme and substrate molecules move slowly
  • Rate of substrate molecules colliding with enzyme is very low
• Optimum temperature


  Where the enzyme is most active
• For most human enzymes, the optimum temperature is about 40-45 °C
• Increasing temperature above the optimum


  Causes a rapid decrease in the rate of enzyme reaction
• Enzyme at high temperatures


  • Active site begins to lose its original shape
  • No longer complementary to the shape of substrate molecules
• At high temperatures all the enzyme molecules have been denatured
• Most enzymes are denatured at high temperatures