Bio Ques of T!

BITS Pilani, K K Birla Goa Campus

First Semester, 2015-2016

Test 1

Biological Chemistry

BIO F211

19.09.2015

Max. Marks 40

Duration: 1.0 Hour

Instructions: Read the instructions for each question carefully. Your answers should be short and to the

point. If your answer is not legible, it will automatically be marked incorrect. Do not spend too much

time on any one question.

Useful Equations:

1. Beer Lambert Law : log I/I0A = = € C L

V

[S]

2. Michaelis-Menten Equation :V= Kmax

+[S]

M

3. Henderson-Hasselbalch Equation: pH = pKa+ log {[A-]/[HA]}

4. The log of a number greater than 1 is a positive number and a less than 1 is a negative number

5. The log of 1 is zero

6. pI = (pKa1 + pKa2) / 2

Q1. At physiological pH (7.0), what will be the predominant form of phosphate present in cells? (H 3PO4?

H2PO4-? HPO4-2, or PO4-3?) Justify your answer using the Henderson-Hasselbalch equation. (Hint: At pH of

more than one unit of pKa, the proton is completely off and vice versa).

(4)

Q2. Aspartame (NutraSweet), an artificial sweetener, is a dipeptide composed of Asp-Phe in which the

carboxyl terminus is modified by the attachmentof a methyl group. Draw the structure of Aspartame at

pH 7.

(4)

Q3. The HRD minister of India, Ms. Smriti Irani, has isolated a protein with the following amino acid

sequence

(6+2=8)

MNARENDRAISTHEKING

(i)

(ii)

She carried out Trypsin digestion (Trypsin cleaves on the carboxy side of Lysine and Arginine

residues). Give the sequence of the resulting fragments and suggest her methods you would

employ to purify them. Briefly explain the principle behind the techniques.

In the course of purifying an enzyme, Ms. Irani performs a purification step that results in an

increase in the total activity to a value greater than that present in the original crude

extract. Explain the possible reason(s) for the increase in the total activity.

Q4. (a) Determine the sequence of a peptide consisting of 14 amino acids on...