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lecture 9

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Terms in this set (20)

  • What are the four levels of protein structure?

    Primary: amino acid sequence
    Secondary: α-helix and β-sheet structures
    Tertiary: 3D folding of a single polypeptide
    Quaternary: assembly of multiple polypeptide chains

  • What distinguishes globular proteins from fibrous proteins?

    Globular proteins are water soluble with hydrophilic residues on the surface; fibrous proteins are insoluble, form fibers or sheets, and have tightly packed hydrophobic residues.

  • Define conjugated proteins and list six types.

    Proteins requiring non-protein components for function: glycoproteins, lipoproteins, metalloproteins, phosphoproteins, hemoproteins, nucleoproteins.

  • What is the oligomeric structure of hemoglobin and myoglobin?

    Hemoglobin has a quaternary structure with 4 polypeptide chains; myoglobin has a tertiary structure with a single polypeptide chain.

  • Where are myoglobin, hemoglobin, and collagen found in the body?

    Myoglobin: muscle tissue
    Hemoglobin: red blood cells
    Collagen: connective tissues like skin, bones, and teeth

  • What physical change in hemoglobin causes sickle cell anemia?

    Mutation of glutamate to valine at residue 6 in β-globin creates a hydrophobic patch causing hemoglobin aggregation and sickled red blood cells.

  • How does electrophoresis separate proteins?

    By charge and size, allowing analysis of protein variants like normal and sickle cell hemoglobin.

  • What diseases are related to collagen misfolding or deficiency?

    Osteogenesis imperfecta (brittle bone disease) and scurvy (vitamin C deficiency affecting collagen synthesis).

  • What bond stabilizes the structure of hair (α-keratin)?

    Disulfide bonds (S-S) between cysteine residues stabilize α-keratin packing.

  • What are chaperones in protein biology?

    Proteins and complexes that assist other proteins in folding correctly and prevent aggregation.

  • Why are prions considered infectious agents?

    Misfolded prions induce normal prions to change shape, causing transmissible spongiform encephalopathies.

  • What is protein degradation and where does it occur?

    Breakdown of proteins by hydrolysis of peptide bonds; occurs in lysosomes and proteasomes.

  • What bond is broken during protein degradation?

    The peptide bond between amino acids is cleaved during proteolysis.

  • What causes protein denaturation?

    Heat, mechanical agitation, detergents, organic solvents, pH changes, and high salt concentrations disrupt non-covalent interactions.

  • What is the function of myoglobin in muscles?

    Stores oxygen and facilitates oxygen diffusion in muscle cells.

  • How does oxygen binding affect hemoglobin structure?

    Oxygen binding causes conformational changes in hemoglobin's quaternary structure, enhancing oxygen transport.

  • Why does myoglobin have higher oxygen affinity than hemoglobin at low oxygen concentrations?

    Myoglobin binds oxygen more tightly to store it in muscles, especially at low pO2 like in capillaries.

  • What amino acid is critical for close packing in collagen's triple helix?

    Glycine, every third residue, allows tight packing of the three collagen strands.

  • What role does vitamin C play in collagen synthesis?

    Vitamin C is required to hydroxylate proline residues, stabilizing collagen's triple helix.

  • What is autophagy in protein degradation?

    A self-degradative process removing misfolded proteins and damaged organelles to maintain cellular health.