2. Proteins

• What are the functions of proteins?

  • Catalyze reactions (enzymes)
  • Transport molecules (carrier proteins)
  • Defend against disease (antibodies)
  • Support cells and tissues (structural proteins)
  • Transmit information (hormones)
  • Carry oxygen (transport proteins)
  • Enable muscle contraction (contractile proteins)
• Why can proteins perform a wide range of biological functions?

  Each protein has a specific molecular shape
• What is the basic structure of an amino acid?

  • Carboxyl group (-COOH)
  • Amino group (-NH2)
  • Central carbon atom (C)
  • Variable group (R)
• How many different naturally occurring amino acids are there?

  20
• What is the primary structure of proteins?

  The order of amino acids in a chain
• What are proteins made up of?

  C, H, O, N, and some S and P
• What happens during a condensation reaction between amino acids?

  A water molecule is removed, forming a peptide bond
• What is the bond called that joins two amino acids?

  Peptide bond
• What is hydrolysis in relation to proteins?

  Addition of water that breaks peptide bonds
• What are the four structural levels of proteins?

  1. Primary structure: sequence of amino acids
  2. Secondary structure: initial folding (alpha helix, beta pleated sheet)
  3. Tertiary structure: 3D shape from R-group interactions
  4. Quaternary structure: multiple polypeptide chains
• What type of bonds are present in the secondary structure of proteins?

  Hydrogen bonds
• What maintains the tertiary structure of proteins?

  Interactions between R-groups
• What is the role of disulfide bridges in proteins?

  Provide further support to the protein structure
• What is quaternary structure in proteins?

  Multiple polypeptide chains working together
• What types of bonds hold the four structural levels of proteins together?

  • Peptide bonds (primary)
  • Hydrogen bonds (secondary and tertiary)
  • Ionic bonds (tertiary)
  • Disulfide bonds (tertiary)
  • Hydrophobic and hydrophilic interactions (tertiary)
• What happens to ionic bonds in proteins when pH changes?

  They can be split by changing pH
• What defines the R group in amino acids?

  It varies among different amino acids
• How do amino acids act as buffers?

  They can accept or release H+ ions
• What is the reaction that joins two amino acids together?

  Condensation reaction
• What determines the final 3D structure of a protein?

  The interactions between R-groups
• What are the four structural levels in proteins?

  Primary, secondary, tertiary, quaternary
• What type of bond holds the primary structure of proteins together?

  Peptide bonds
• Which bonds are involved in the secondary and tertiary structures of proteins?

  Hydrogen bonds
• What types of bonds are found in the tertiary structure of proteins?

  Ionic, disulphide, hydrogen
• What does the quaternary structure of a protein depend on?

  The 3D structure of individual polypeptides
• What are the two groups found in all amino acid molecules?

  Amine group and carboxyl group
• What reaction joins amino acids together in proteins?

  Condensation reaction
• What determines the final 3D structure of a protein?

  The order of amino acids in the primary sequence
• How does a secondary structure become a tertiary structure?

  Through interactions between R-groups of amino acids
• What are the two main groups of proteins?

  Globular proteins and fibrous proteins
• Why are globular proteins soluble in water?

  Due to hydrophilic R groups that point outwards
• What is the role of enzymes in metabolic reactions?

  They catalyze intracellular reactions
• What is the structure of hemoglobin?

  It has 4 polypeptide chains
• How does the structure of hemoglobin contribute to its function?

  Hydrophilic side r groups outwards for solubility
• What type of protein is collagen?

  Fibrous protein
• What is the overall structure of fibrous proteins?

  They form long chains or fibers
• Why are fibrous proteins insoluble in water?

  Due to their fibrous nature
• What is the role of collagen in living organisms?

  Provides strength and support to tissues
• How do the structures of collagen and hemoglobin differ?

  Collagen is fibrous, hemoglobin is globular
• What stabilizes the structure of collagen?

  Covalent cross-links between collagen molecules