Question

please help with these 4 questions and explain why you chose what you did. thanks and I'll give thumbs up.

11. A particular amino acid without an ionizable R-group would have a pl of is 3.1 and pK2 is 8.9 ; if its pK1 2.9 a. b. 5.8 6 C. d. 12 12. A certain amino acid with an ionizable side chain has a pK1 of 2.4, a pK2 of 8.9, and a pKR of 6.5. If the amino acid has a zero net charge between pKR and pK2, what is its pl? 4,5 a. b. 5.7 7,7 c. d. 8.9 13. A protein would least likely be denatured by what reagents or conditions? Low pH a. b. High Temperature High Salt content C. d. Urea 14. Protein A will fold into its native conformation only when protein B is also present. However, protein B can fold into its native conformation without protein A Protein B, therefore, may function for protein A as a Motif e. f. Antigen g. Chaperone h. Protease

Answer 1

Solution:

11) Option C

Isoelectric point (pI) is calculated as:

pI = (pk1 + pk2) / 2 = (3.1 + 8.9) / 2 = 6

12) Option C

At pI, the amino acid contains net zero charge. Hence, pI is calculated by using pk2 and pkR.

Thus,

pI = (pk2 + pkR) /2 = (8.9 + 6.5 /2 ) = 15.4/2 = 7.7

13) Option D

Low pH ( acidic) , High salt content and high temperature are the major factor for denaturation of proteins.

Urea denatured proteins indirectly via, solvent interactions. Thus, it is considered as least factor for denaturation.

14) Option g

Protein B may function as chaperone for protein A. Folding of many proteins are facilated by the action of special proteins called chaperone.