Answer Happy

1 Which of these statements is FALSE? a) The peptide bond exists in two forms, cis and trans. b) In most cases the peptide bond will be in the more energetically favourable trans conformation. c) The only freely rotating bonds in the polypeptide backbone are the N-alpha-C bonds and alpha-C-C, known as phi and psi respectively. T d) The conformational freedom of the polypeptide chain derives from these two rotational angles e) The conformational freedom of a polypeptide chain is always determined by the presence or absence of the two amino acid residues, glycine and proline. 2. Which of these acidic amino acids fold inwards in proteins? a) phenylalanine b) proline c) tyrosine d) tryptophan e) all of the above 3- Which of the following statements about protein structure is/are correct? a) Alpha-helix is stabilized primarily by the presence of numerous hydrophobic interactions. b) Beta structure involves hydrogen bonding between extended regions in a parallel direction only. c) Quaternary structure refers to the cross-linking of globular proteins with disulfide bonds. +d) Disulfide bonds are formed after the polypeptide has folded into its three dimensional structure. A. Mark answer 'A' if statements 1, 2 and 3 are correct. B. Mark answer 'B' if statements 1 and 3 are correct. C. Mark answer 'C' if statements 2 and 4 are correct. D. Mark answer 'D' if ONLY statement 4 is correct. E. Mark answer 'E' if statements are ALL correct, or they are ALL incorrect. 4 Which of the following is an essential amino acid? A Glutamine B Proline C Methionine D Cysteine E Asparagine 0