Proteins

• What are the two main types of protein structures in aqueous solutions?

  Globular and fibrous structures
• Why are globular proteins generally spherical in shape?


  Due to charged groups on the outer surface attracting water molecules
• What is the structural composition of fibrous proteins?


  Made from straight chain polypeptides held by hydrogen bonding
• What contributes to the resistance of fibrous proteins to attacks?

  The presence of crosslinks and many disulphide bridges
• What is the test used to detect proteins?

  The Biuret test
• What is the procedure for the Biuret test?

  Add sodium hydroxide and dilute copper (II) sulfate to the sample
• What color indicates the presence of peptide bonds in the Biuret test?


  Purple
• What are the four main types of biological macromolecules and their monomers?


  • Carbohydrates: Monosaccharides (e.g., fructose)
  • Proteins: Amino Acids
  • Nucleic Acids: Nucleotides
  • Lipids: Fatty acids and glycerol
• What are the types of covalent bonds associated with each macromolecule?


  • Carbohydrates: Glycosidic bond
  • Proteins: Peptide bond
  • Nucleic Acids: Phosphodiester bond
  • Lipids: Ester bond
• What are examples of polymers for each type of macromolecule?


  • Carbohydrates: Glycogen, cellulose, starch
  • Proteins: Polypeptides (e.g., enzymes)
  • Nucleic Acids: DNA, RNA
  • Lipids: Triglycerides, phospholipids
• How do enzymes function in biochemical reactions?


  They act as catalysts to lower activation energy
• What is the structure of enzymes?


  They are 3D tertiary structure globular proteins
• What is the role of the active site in an enzyme?


  It is specific to the substrate and forms an enzyme-substrate complex
• What models describe the interaction between enzymes and substrates?


  The Lock and Key model and the Induced Fit model
• How do enzymes speed up reactions at lower temperatures?


  By making bond formation easier and reducing strain to break bonds
• What happens to the rate of reaction as temperature increases?


  It increases until a denaturation point is reached
• What is the optimum temperature for enzyme activity?


  It is the temperature at which the maximum rate of reaction occurs
• How many amino acids are there in nature?


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


  H₂N - C - C - OH with a variable R group
• What is formed when two amino acids bond together?


  A peptide bond is formed through condensation
• What is the structure of a peptide bond?


  It is formed between the carboxyl group of one amino acid and the hydrogen group of another
• What are the four levels of protein structure?

  1. Primary: Sequence of amino acids
  2. Secondary: Alpha helices and beta-pleated sheets formed by hydrogen bonds
  3. Tertiary: 3D shape maintained by various bonds
  4. Quaternary: Multiple polypeptide chains working together
• What stabilizes the secondary structure of proteins?


  Hydrogen bonds between the main chain groups
• What maintains the tertiary structure of proteins?


  Hydrogen bonds, ionic bonds, and disulphide bridges
• What are disulphide bridges in proteins?


  Intermolecular covalent bonds formed between sulfur atoms in cysteine
• What type of bonds can occur between positively and negatively charged R groups?


  Ionic bonds