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GOB Chemistry: Protein Structure and Function

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Terms in this set (20)

  • What are the four levels of protein structure?

    Primary: amino acid sequence.
    Secondary: local folding into α-helices or β-sheets.
    Tertiary: 3D structure 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 form insoluble fibers or sheets with tightly packed hydrophobic residues.

  • Define conjugated proteins and list six types.

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

  • What is the oligomeric structure of hemoglobin?

    Hemoglobin has a quaternary structure composed of four polypeptide chains (2 α and 2 β chains).

  • What is the structure and function of myoglobin?

    Myoglobin is a tertiary structure globular protein found in muscles that stores oxygen.

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

    Myoglobin: muscles.
    Hemoglobin: red blood cells.
    Collagen: connective tissues like bones, skin, and tendons.

  • What physical change in hemoglobin causes sickle cell anemia?

    A mutation replaces glutamate (hydrophilic) with valine (hydrophobic) at residue 6 of the β chain, causing hemoglobin aggregation and sickled red blood cells.

  • How does electrophoresis separate proteins?

    Electrophoresis separates proteins based on their charge and sometimes size by applying an electric field through a gel matrix.

  • What diseases are related to collagen misfolding or deficiency?

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

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

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

  • What are chaperone proteins?

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

  • Why are prions called infectious agents?

    Prions induce normally folded proteins to misfold into β-sheet rich structures, propagating infectious misfolded proteins.

  • What is protein degradation and where does it occur?

    Protein degradation is the breakdown of proteins into amino acids, occurring mainly in lysosomes and proteasomes.

  • What bond is broken during protein degradation/proteolysis?

    The peptide bond between amino acids is cleaved during proteolysis.

  • What happens to a protein during hydrolysis?

    Hydrolysis breaks peptide bonds, resulting in the breakdown of the protein into individual amino acids.

  • What causes protein denaturation?

    Denaturation is caused by heat, mechanical agitation, detergents, organic solvents, pH changes, and high salt concentrations disrupting non-covalent interactions.

  • Is protein denaturation a physical or chemical process?

    Protein denaturation is primarily a physical process disrupting structure without breaking peptide bonds.

  • What is the role of vitamin C in collagen synthesis?

    Vitamin C is required for hydroxylation of proline residues, stabilizing collagen triple helix formation.

  • How does sickle cell hemoglobin aggregation occur?

    The hydrophobic valine at position 6 fits into a hydrophobic pocket on another hemoglobin molecule, causing aggregation into fibrous strands.

  • What is the difference in oxygen affinity between myoglobin and hemoglobin?

    Myoglobin has a higher oxygen affinity at low oxygen concentrations, facilitating oxygen storage in muscles, while hemoglobin releases oxygen in tissues.