Proteins and Enzymes

• What are proteins made from?

  Long chains of amino acids
• What is a dipeptide?

  A molecule formed from two amino acids
• What is a polypeptide?

  A molecule formed from more than two amino acids
• What are the monomers of proteins?

  Amino acids
• What is the general structure of an amino acid?

  • Carboxyl group (-COOH)
  • Amino group (-NH₂)
  • R group (variable side group)
• How many different amino acids do all living things share?

  20 amino acids
• What determines the properties of different amino acids?

  The composition of their R groups
• How are polypeptides formed?

  By condensation reactions between amino acids
• What type of bond is formed between amino acids?

  Peptide bonds
• What are the four structural levels of proteins?

  1. Primary structure: sequence of amino acids
  2. Secondary structure: coiling or folding of the chain
  3. Tertiary structure: further coiling and folding
  4. Quaternary structure: assembly of multiple polypeptide chains
• What is the primary structure of a protein?

  The sequence of amino acids in the chain
• What happens in the secondary structure of proteins?

  Hydrogen bonds cause coiling or folding
• Why are enzymes highly specific?

  Only one substrate fits their active site
• What is activation energy?

  The energy needed to start a reaction
• How do enzymes lower activation energy?

  By forming enzyme-substrate complexes
• What is the 'lock and key' model of enzyme action?

  • Substrate fits into the enzyme's active site
  • Enzyme remains unchanged after the reaction
  • Simplified model of enzyme specificity
• What is the 'induced fit' model of enzyme action?

  • Enzyme changes shape to fit substrate
  • Enhances binding of substrate to active site
  • Explains enzyme specificity more accurately
• What happens to the active site if the enzyme's tertiary structure is altered?

  The active site changes shape and won't fit
• What factors can alter the tertiary structure of an enzyme?

  Changes in pH or temperature
• How does a mutation in a gene affect enzyme function?

  It can change the enzyme's tertiary structure
• What is the optimum temperature for most human enzymes?

  About 37°C
• What happens to enzymes at high temperatures?

  They become denatured and stop functioning
• How does temperature affect enzyme activity?

  Higher temperatures increase reaction rates until denaturation
• What are the factors affecting enzyme activity?

  • Temperature
  • pH
  • Substrate concentration
  • Enzyme concentration
• How does temperature influence enzyme activity?

  Higher temperatures increase reaction rates until denaturation.
• What happens to enzyme molecules as temperature rises?

  They vibrate more.
• What occurs if the temperature exceeds a certain level for enzymes?

  Bonds holding the enzyme's shape break.
• What is the result of the active site changing shape?

  The enzyme and substrate no longer fit together.
• What is it called when an enzyme no longer functions as a catalyst?

  Denaturation
• What is the optimum temperature for most human enzymes?

  37°C
• How does pH affect enzyme activity?

  Each enzyme has an optimum pH value.
• What is the optimum pH for most human enzymes?

  pH 7
• What is an exception to the optimum pH for human enzymes?

  Pepsin works best at pH 2.
• How do H+ and OH- ions affect enzymes?

  They can disrupt ionic and hydrogen bonds.
• What happens to the active site when the enzyme is denatured?

  It changes shape.
• How does enzyme concentration affect the rate of reaction?

  More enzymes increase the reaction rate.
• What limits the effect of increasing enzyme concentration?

  Limited substrate availability.
• How does substrate concentration affect the rate of reaction?

  Higher substrate concentration increases reaction rate.
• What is the saturation point in enzyme reactions?

  When active sites are full.
• What happens to substrate concentration over time during a reaction?

  It decreases unless more is added.