Question

questions e-f and g.and k.

a) Use the 3 letter symbols for a 6 amino acid peptide chain containing at least one polar and at least one acidic or basic amino acid. (All at physiological pH.) Asp - Gly-Glu-Tyr- Phe- Ala OM b) Draw the primary structure with its peptide bonds, side chains, etc. in the correct order. CH3 NH - E-N -CH. - CH - C- 2-I U=0 -ch- & N-chi- CH₃ CH ₂ Coo CH н My Coo c) Name the amino acids in the polypeptide you have just created in the correct order. Acid, Glycine, Glutamic acid, Aspertic Alanine Tyrosine, phenalanaline, d) Is your polypeptide more hydrophobic or more hydrophilic?— budrophobica e) What would its net charge be at pH 3? 1) Why would it migrate toward the cathode or the anode or stay stationary during electrophoresis at physiological pH?

Answer 1

e) the average pI of amino acids is around 5.5 and so at pH = 3, there will be more H+ ions due to which they will exhibit positive charges net charge would be positive.

f) at physiological pH=7.4, that means slightly basic, so it would if exists as negative ions, then would migrate towards positive electrode and if exist as positive then towards negative electrode.

g) the type of intermolecular forces present in polypeptides is H-bonding which is between the H amino group and O of carbonyl group.

k) only primary (1 degree) structure will not be affected by the denaturation because in primary structure there is sequence of amino acids and these amino acids are joined by covalent bonding (primary srtucture) while in other structures, there is H-bonding (secondary bonding) responsible, which is weaker as compared to covalent bonding, so easily reptured leadgin to denaturation.