Glucose residues in amylose are linked by

• β1 → 4

• ∝1 → 4

• ∝1 → 6

• β1 → 6

Haemoglobin has characteristic circular dichroism (CD) peaks C in the far-UV, near UV and Soret regions. contribution to near-UV CD comes entirely from

• aromatic  amino acid residues

• heme groups

• heme and aromatic amino acid residues

• peptide bond and aromatic amino acid residues

Tryptic digest of a heptapeptide (built from 3 lysine (K), 2 alanine (A), 1 tyrosine (Y), and 1 phenylalanine (F)) yielded tri and tetrapeptide. Which of the following is the correct sequence of the heptapeptide?

• KAYAKFK

• YKAAFKK

• KYKAAKF

• KYAAKFK

100 mL of 0.1 M sodium acetate solution has a pH of 8.90. To this solution 1000μl of 1 M acetic acid (pKa = 4.76) of pH 2.80 is added. The pH of this mixture will be:

• 8.90

• 4.76

• 2.80

• 5.76

What are A, B, and C in the following reactions?

• Pyruvate, ribose 5-phosphate, glycogen

• Ribose 5-phosphate, glycogen, pyruvate

• Glycogen, pyruvate, ribose 5-phosphate

• Glycogen, citrate, ribose 5-phosphate

Michaelis-Menten enzyme kinetics for simple reaction involving an enzyme (E) and substrate (S) is given by the scheme:

E + S $\rightleftharpoons$E S $\stackrel{{\mathrm{k}}_{\mathrm{cat}}}{\rightleftharpoons }$ E + P

The description of K_m, k_cat, and their relationship is provided in the following statements.

A. K_m represents the association constant of the ES complex.

B. K_m represents the dissociation constant of the ES complex.

C. k_cat is the rate constant for the chemical conversion of the ES complex to substrate-bound enzyme and product.

D. k_cat/ K_m is a rate constant that refers to the properties and reactions of the free enzyme and free substrate.

Which of the combinations of the above statements is true?

• A and C

• B and D

• A and D

• B and C

A 26-residue peptide composed of alanine and leucine shows a circular dichroism (CD) spectrum characteristic of α-helix at 50°C in 5 mM phosphate buffer at pH 7.4. Deconvolution of the spectrum indicates 60% α-helical and 40% random conformation. When the peptide solution is cooled gradually to 25°C, and the CD spectra are recorded at different temperatures, the most likely observation will be that

• the % helical content will decrease and % random conformation will increase

• the % helical content will increase and % random conformation will decrease

• there will be transition from α-helix to β-sheet

• there will be transition from α-helix to β-hairpin

It has been observed that for the DNA double helix melting, the value of $∆$H (enthalpy change of denaturation) are 80 and 90 kcal/ mole at 70° and 80°C, respectively. Assuming that $∆$C_p (constant-pressure heat capacity change) is independent of temperature, estimate $∆$H associated with the denaturation of DNA at 37°C. This estimated value of $∆$H (kcal/ mole) is

• 27

• 37

• 47

• 57

The electrospray ionization spectrum of a highly purified protein shows multiple closely spaced peaks. This most likely arises due to

• degradation of the protein during recording of the spectrum.

• the presence of multiple conformations.

• multiple charged species of the protein.

• extensive aggregation of the protein.

The average energy absorbed by 10 gm of tissue from ³²P radiation is 14.9 Jkg^-1. The average dose in rads is

• 1490

• 1.49

• 14900

• 149