Proteins and enzymes

• Identifying non-reducing sugars


  Heat sample with dilute HCl, neutralise with sodium hydrogen carbonate, heat with Benedict's
• What are the monomers of proteins?

  Amino acids
• What is the significance of the R group in amino acids?

  It differentiates the 20 amino acids
• What is formed when two amino acids join?

  A dipeptide
• What is a polypeptide?

  More than two amino acids joined
• How are proteins formed?

  From one or more polypeptides
• How are amino acids linked together?

  By condensation reactions
• What are the bonds formed between amino acids called?

  Peptide bonds
• What happens to the solution if protein is present in the Biuret test?

  It turns from light blue to purple
• What are the levels of protein structure?

  1. Primary: Sequence of amino acids
  2. Secondary: Alpha helix and beta pleated sheet
  3. Tertiary: Coiled and folded polypeptide chain
  4. Quaternary: Assembly of multiple polypeptide chains
• What characterizes the secondary structure of proteins?

  Formation of alpha helix and beta sheets
• What type of bonds form in the tertiary structure of proteins?

  Hydrogen bonds and ionic bonds
• What are disulfide bridges?

  Bonds between cysteine molecules
• What is the quaternary structure of proteins?

  Assembly of multiple polypeptide chains
• What are enzymes classified as?

  Biological catalysts
• What do enzymes do?

  Speed up chemical reactions
• How do enzymes affect metabolic reactions?

  They catalyze respiratory and digestive reactions
• What is the active site of an enzyme?

  The specific region where substrates bind
• Why are enzymes highly specific?

  Due to their tertiary structure
• What is activation energy?

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

  By forming enzyme-substrate complexes
• What happens when two substrate molecules are joined by an enzyme?

  They are held close together to bond easily
• How does an enzyme facilitate a breakdown reaction?

  It strains bonds in the substrate
• What are the two models of enzyme action?

  1. Lock and Key model
  2. Induced Fit model
• What does the induced fit model suggest?

  The active site changes shape to fit the substrate
• How are enzyme properties related to their structure?

  They depend on the enzyme's tertiary structure
• What can alter the shape of an enzyme's active site?

  Changes in pH or temperature
• What effect can a mutation have on an enzyme?

  It can change the tertiary structure