A-LevelBiologyBiological molecules9700/12 · Oct/Nov 2021 · Q131 Mark
Which row is correct about the structure of proteins? [Table describing primary, secondary, tertiary, and quaternary protein structures]
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Aprimary: determined by the sequence of DNA nucleotides; secondary: occurs by hydrogen bonding between NH and C=O groups of amino acids; tertiary: disulfide, ionic, hydrogen bonds and hydrophobic interactions are all involved; quaternary: always formed by association of two or more polypeptides
Bprimary: the number of amino acids in each polypeptide chain; secondary: in a single polypeptide it is either an α-helix or a β-pleated sheet; tertiary: the bonds are formed at specific points determined by the primary structure; quaternary: always formed by two or more polypeptides held together by bonds formed between the polypeptides
Cprimary: formed by twenty different amino acids linked in a specific order; secondary: an α-helix is formed by hydrogen bonds between side chains of amino acids; tertiary: only globular proteins have this level of structure; quaternary: always formed by two or more different polypeptides to give the final shape
Dprimary: the sequence of amino acids in each polypeptide chain; secondary: a β-pleated sheet is the result of a folded polypeptide forming hydrogen bonds between adjacent strands; tertiary: reactions between side chains of specific amino acids give a specific 3-D shape; quaternary: always formed by two or more polypeptides and a metal ion
✓ Correct answer
A: primary: determined by the sequence of DNA nucleotides; secondary: occurs by hydrogen bonding between NH and C=O groups of amino acids; tertiary: disulfide, ionic, hydrogen bonds and hydrophobic interactions are all involved; quaternary: always formed by association of two or more polypeptides
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