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GOB Chemistry: Protein Structure and Function

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  • What defines a protein's tertiary structure?
    The tertiary structure consists of a single polypeptide chain folded into a 3D shape stabilized by covalent and noncovalent interactions.
  • What characterizes quaternary protein structure?
    The quaternary structure consists of multiple protein chains (subunits) assembled into a functional complex.
  • Difference between globular and 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.
  • What are conjugated proteins?
    Proteins that require non-protein components for function, such as glycoproteins, lipoproteins, metalloproteins, phosphoproteins, hemoproteins, and nucleoproteins.
  • Function and structure of myoglobin?
    Myoglobin is a tertiary globular protein found in muscles that stores oxygen with a single polypeptide chain and a heme group.
  • Function and structure of hemoglobin?
    Hemoglobin is a quaternary globular protein in red blood cells that transports oxygen; it has four polypeptide chains each with a heme group.
  • What causes sickle cell anemia at the molecular level?
    A mutation replacing glutamate with valine at residue 6 in hemoglobin's beta chain creates a hydrophobic patch causing hemoglobin aggregation and sickled red blood cells.
  • How does electrophoresis separate proteins?
    Electrophoresis separates proteins based on their charge and molecular weight by moving them through a porous gel under an electric field.
  • What is collagen and its structure?
    Collagen is a tough, insoluble fibrous protein with a quaternary structure made of three tropocollagen strands stabilized by hydrogen bonds and covalent crosslinks.
  • Which amino acid allows close packing in tropocollagen?
    The abundance of glycine residues every third position allows tight packing of the three collagen strands.
  • Diseases related to collagen defects?
    Osteogenesis imperfecta (brittle bone disease) and scurvy (vitamin C deficiency affecting hydroxylation of proline) are related to collagen misfolding or deficiency.
  • What stabilizes the structure of hair?
    Hair structure is stabilized by numerous disulfide bonds between cysteine residues in keratin proteins.
  • What stabilizes α-keratin packing?
    Disulfide bonds forming between peptide chains stabilize the packing of α-keratin.
  • What stabilizes β-keratin strands?
    Van der Waals interactions stabilize the packing of β-keratin strands.
  • What are chaperones in protein folding?
    Chaperones are proteins or complexes that assist other proteins in folding correctly and prevent aggregation.
  • Why are prions considered infectious agents?
    Prions induce normally folded proteins to misfold into β-sheet rich structures, propagating infectious misfolded proteins.
  • What diseases do prions cause?
    Prions cause transmissible spongiform encephalopathies (TSEs), rare fatal brain disorders with spongy brain tissue.
  • What is protein degradation?
    Protein degradation is the breakdown of proteins into amino acids by breaking peptide bonds, often via proteolysis.
  • Where does protein degradation occur in cells?
    Protein degradation occurs in lysosomes and proteasomes within cells.
  • What causes protein denaturation?
    Protein denaturation is caused by heat, mechanical agitation, detergents, organic solvents, pH changes, and high salt concentrations disrupting noncovalent interactions.