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Protein Structure exam

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  • What is the basic structure shared by all amino acids?
    A central carbon atom bonded to an amine group, a carboxylic acid group, a hydrogen atom, and a variable R group.
  • Essential amino acids
    Amino acids that cannot be synthesized by the body and must be obtained from the diet.
  • How many different amino acids are used to build proteins in humans?
    20
  • R group (side chain)
    The variable group in an amino acid that determines its unique properties.
  • What determines the unique properties of each amino acid?
    The structure of its R group (side chain).
  • Primary structure of a protein
    The sequence (order, type, and quantity) of amino acids in a polypeptide chain.
  • What is the most important level of protein structure and why?
    Primary structure, because it determines all higher levels of protein structure.
  • Secondary structure of a protein
    Local folding patterns of the polypeptide backbone, such as alpha helices and beta sheets.
  • Alpha helix
    A spiral or winding staircase-like structure formed in the secondary structure of proteins.
  • Beta sheet
    A zigzag, sheet-like structure formed in the secondary structure of proteins.
  • Tertiary structure of a protein
    The overall three-dimensional shape of a single polypeptide chain, determined by R group interactions.
  • What primarily determines the tertiary structure of a protein?
    Interactions between the side chains (R groups) of amino acids.
  • Quaternary structure of a protein
    The association of multiple polypeptide chains to form a functional protein.
  • Do all proteins have quaternary structure?
    No, only proteins with multiple polypeptide chains have quaternary structure.
  • Denaturation
    The alteration of a protein's structure and shape, causing loss of function.
  • What levels of protein structure are affected by denaturation?
    Secondary, tertiary, and quaternary structures; primary structure remains unchanged.
  • Name two ways proteins can be denatured.
    Heat and changes in pH (acids or bases).
  • Why is protein denaturation important in nutrition?
    It helps prepare foods for consumption and is crucial for protein digestion in the stomach.
  • Globular protein
    A protein with a compact, spherical shape, such as hemoglobin.
  • Fibrous protein
    A protein with an elongated, rope-like shape, such as collagen.
  • What is the most abundant protein in the human body?
    Collagen, a fibrous protein.
  • Polypeptide chain
    A long chain of amino acids linked by peptide bonds.
  • How does changing one amino acid in a protein's sequence affect its function?
    It can drastically change or eliminate the protein's function.
  • What is the role of hemoglobin?
    To transport oxygen in red blood cells.
  • Nonessential amino acids
    Amino acids that the body can synthesize and do not need to be obtained from the diet.
  • What makes proteins a critical source of nitrogen in the diet?
    The presence of nitrogen in the amine group of amino acids.
  • What is meant by the term 'protein backbone'?
    The repeating sequence of the central carbon, amine group, and carboxylic acid group in a polypeptide chain.
  • How many amino acids are essential for humans?
    Nine
  • What is a peptide bond?
    A covalent bond linking the carboxyl group of one amino acid to the amine group of another.