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Lecture 8 & 9: Protein Structure and Function

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Terms in this set (26)

  • What are the four classes of biomacromolecules in the human body?

    Carbohydrates, lipids, proteins, and nucleic acids.

  • What roles do proteins play in the body?

    Enzymes (speed reactions)

    provide structure (collagen/keratin),

    transport (hemoglobin),

    signaling (hormones/receptors)

    defense (antibodies).

  • Why is protein structure important?

    The shape dictates function; the amino acid sequence folds into a shape determining binding and activity.

  • What is the general structure of an amino acid?

    Central (alpha) carbon bonded to an amino group, carboxyl group, hydrogen atom, and a side chain (R group).

  • What is a chiral carbon?

    A carbon atom bonded to four different groups

    • allowing for mirror-image molecules called enantiomers.

  • What are constitutional isomers? Give an example.

    Isomers differing in bonding order of atoms

    H3C-CH2-OH and H3C-O-CH3.

  • What are stereoisomers and their subtypes?

    Isomers with same bonding order but different spatial arrangement: enantiomers (mirror images)

    diastereoisomers (not mirror images, multiple chiral centers).

  • How are amino acids classified by side chain properties?

    Nonpolar (hydrocarbons, hydrophobic)

    neutral polar (contain O, N, or S, hydrophilic)

    acidic (carboxylic acid, negative charge)

    basic (nitrogens, positive charge).

  • What are zwitterions in amino acids?

    Amino acids with both positive (amine) and negative (carboxyl) charges at pH 7, making them dipolar.

  • Which amino acids have charged side chains?

    Acidic amino acids have negative charges

    basic amino acids have positive charges at physiological pH.

  • What is the primary structure of a protein?

    The exact linear sequence of amino acids linked by peptide bonds,

    • read from N-terminus to C-terminus.

  • Why are glycine, proline, and cysteine shape-determining amino acids?

    Glycine is small and flexible;

    proline has a rigid ring causing kinks;

    cysteine forms disulfide bonds stabilizing structure.

  • What are the main secondary structures in proteins?

    Alpha-helix (coiled, stabilized by H-bonds 4 residues apart) and beta-pleated sheets (strands linked by H-bonds).

  • What interactions stabilize each protein structure level?

    Primary: peptide bonds;

    Secondary: H-bonds between backbone groups;

    Tertiary: hydrophobic, H-bonds, ionic, van der Waals, disulfide bonds;

    Quaternary: same as tertiary but between subunits.

  • Describe the structure and type of collagen, keratin, hemoglobin, and myoglobin.

    Collagen: fibrous, quaternary triple helix;

    Keratin: fibrous, quaternary coiled bundles;

    Hemoglobin: globular, quaternary with 4 subunits;

    Myoglobin: globular, tertiary single chain.

  • What are conjugated proteins? Name six types.

    Proteins with covalently bound groups: glycoproteins, lipoproteins, metalloproteins, phosphoproteins, hemoproteins, nucleoproteins.

  • What is the role of myoglobin, hemoglobin, and collagen?

    Myoglobin stores oxygen in muscles;

    hemoglobin transports oxygen in blood;

    collagen provides structural support in connective tissues.

  • What structural change causes sickle cell anemia?

    Hemoglobin molecules form long, rigid, sickle-shaped fibers causing distorted red blood cells.

  • What does SDS-PAGE electrophoresis reveal about proteins?

    Protein size (molecular mass) by denaturing proteins and giving them uniform negative charge for separation by size.

  • What diseases are linked to collagen defects?

    Scurvy (vitamin C deficiency) and Osteogenesis imperfecta (brittle bone disease) due to poor collagen quality or quantity.

  • What bond stabilizes hair structure?

    Disulfide bonds between cysteine residues.

  • What are chaperone proteins?

    Proteins that assist other proteins in folding correctly within the cell.

  • How does the cell degrade unwanted or misfolded proteins?

    Via autophagy (vesicle delivery to lysosomes), proteasomes (proteolysis), and lysosomes (recycling).

  • Why are prions infectious agents and what diseases do they cause?

    Prions are misfolded proteins that induce misfolding in normal proteins, causing fatal neurodegenerative diseases called transmissible spongiform encephalopathies (TSEs).

  • What is protein denaturation and what causes it?

    Loss of normal 3D structure due to disruption of H-bonds, ionic, and hydrophobic interactions by heat, pH changes, detergents, mechanical agitation, organic solvents, or salts.

  • What happens during protein hydrolysis?

    Peptide bonds are broken by adding water, splitting the protein into smaller peptides or amino acids.