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lecture 8

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Terms in this set (20)

  • What is Biochemistry?

    Biochemistry is the study of the chemistry of life and all chemical reactions in living organisms.

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

    The four classes are proteins, lipids, carbohydrates, and nucleic acids.

  • What roles do proteins play in the body?

    Proteins act as enzymes (biological catalysts), hormones, storage, transport, structural, protective, and contractile proteins.

  • What is the general structure of an amino acid?

    An amino acid has a central alpha carbon (Cα) bonded to an amine group, a carboxylic acid group, a hydrogen atom, and a variable side chain (R group).

  • What is a chiral carbon?

    A chiral carbon is a carbon atom bonded to four different chemical groups or atoms, resulting in non-superimposable mirror images (enantiomers).

  • What are the types of isomers relevant to amino acids?

    Constitutional isomers differ in bonding order; stereoisomers have the same bonding order but differ in spatial arrangement, including enantiomers (mirror images) and diastereoisomers (not mirror images).

  • How are amino acids classified based on side chain properties?

    Amino acids are classified as nonpolar, neutral polar, acidic, or basic based on their side chain's chemical groups and charge.

  • What are zwitterions in amino acids?

    Zwitterions are amino acids with both positive (amine) and negative (carboxylate) charges simultaneously, typically at physiological pH (~7).

  • Which amino acid side chains are charged at physiological pH?

    Acidic amino acids have negatively charged side chains; basic amino acids have positively charged side chains at pH 7.

  • What is the primary structure of a protein?

    The primary structure is the linear sequence of amino acids linked by peptide bonds, written from the N-terminus to the C-terminus.

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

    Glycine is flexible due to its small side chain; proline has a rigid cyclic structure affecting backbone conformation; cysteine forms disulfide bonds stabilizing tertiary structure.

  • What are the main secondary structures in proteins?

    The main secondary structures are the alpha-helix and the beta-pleated sheet, stabilized primarily by hydrogen bonds between backbone amide groups.

  • What interactions stabilize protein structures at different levels?

    Primary structure: covalent peptide bonds; secondary: hydrogen bonds; tertiary and quaternary: hydrophobic interactions, hydrogen bonds, ionic bonds (salt bridges), and disulfide bonds.

  • What is the hydrophobic effect in protein folding?

    The hydrophobic effect is the exclusion of water by nonpolar side chains, causing them to pack inside the protein, driving folding.

  • How is an alpha-helix stabilized?

    An alpha-helix is stabilized by hydrogen bonds between the amide hydrogen of one amino acid and the carbonyl oxygen four residues earlier.

  • How are beta-pleated sheets stabilized?

    Beta-sheets are stabilized by hydrogen bonds between amide groups on adjacent beta-strands, which can be parallel or antiparallel.

  • What is a peptide bond?

    A peptide bond is a covalent amide bond formed between the carboxyl group of one amino acid and the amine group of another, releasing water.

  • What is the significance of disulfide bonds in proteins?

    Disulfide bonds are covalent bonds formed between thiol groups of cysteine residues, stabilizing tertiary and quaternary protein structures.

  • Which amino acid class prefers hydrophobic environments?

    Nonpolar amino acids prefer hydrophobic environments and tend to be buried inside protein structures away from water.

  • What functional groups in amino acids can act as hydrogen bond donors?

    The amine group (-NH3+) and amide groups can act as hydrogen bond donors in amino acids.