Question

1. What type of secondary structure would a peptide composed only of the amino acid Lysine form?

a) a random coil at all pH values

b) alpha helix at pH 7

c) alpha helix at pH well above 7

d) alpha helix at pH well below 7

2. During vigorous exercise ATP is hydrolyzed as follows,

ATP----> ADP +Pi + (H+)

what are the consequences of this for the structure-function of hemoglobin?

a) hemoglobin binds O2 stronger as a result of the changing pH

b) lower pH results in deprotonation of His146 which destabilizes the ion pair between monomers

c) lower pH results in protonation of His146 which stabilizes the ion pair between monomers

d) nothing happens to hemoglobin, only myoglobin is affected.

3. If you were to make a mutation to hemoglobin so that it could no longer form tetramers, what would you predict would occur.

a) impossible to predict

b) it would bind oxygen with lower affinity than before

c) it would transport oxygen better

d) hemoglobin would no longer be able to transport oxygen

Answer 1

1.c) Secondary structure of peptide composed only of the amino acid Lysine form a Alpha helix at pH well above 7 of .Lysin composed of an α-amino group which is in the protonated −NH3+ under biological conditions, an α-carboxylic acid group which is in the deprotonated −COO−  under biological conditions, and a side chain lysyl ((CH2)4NH2) is classified  as a basic charged at physiological pH. Lysine is aliphatic amino acid. Lysine can also give stability to peptide as its ε-amino group form hydrogen bonding, salt bridges and covalent interactions to form a Schiff base .

2.c) Lower pH results in protonation of His146 which stabilizes the ion pair between monomers. During exercise cells release H+, CO2, and lactate into blood capillaries, higher temperature in working muscle which causes a rapid decrease in Hb-O2 affinity. H+ allosterically inhibits the oxygen binding to the Hemoglobin.

3.d)Hemoglobin would no longer be able to transport oxygen .Mutation in hemoglobin so that it could no longer form tetramers is a abnormal form of haemoglobin and which results in excessive lysis of reb blood cells and causes anemia. Hemoglobin is the protein molecule in red blood cells that carries oxygen and transport oxygen.