From the following statements,

A. For a reaction to occur spontaneously the free energy change must be negative.

B. The interaction between two nitrogen molecules in the gaseous state is predominantly electrostatic.

C. By knowing bond energies, it is possible to deduce whether the bond is covalent bond or hydrogen bond.

D. Hydrophobic interactions are not important in a folded globular protein.

Pick the combination with ALL Wrong statements.

• A and B

• B and C

• C and D

• B and D

The following are four statements on peptide/ protein conformation:

A. Glycine has the largest area of conformational allowed space in the Ramachandran plot of φ and ψ.

B. A 20-residue peptide that is acetylated at the N-terminus and amidated at the C-terminus has φ = -60° (±5), ψ = -30° (±5) for all the residues. It can be concluded that conformation of the peptide is helix-turn-strand.

C. The allowed value of φ, ψ for amino acids in a protein are not valid for short peptides.

D. A peptide Acetyl-A₁-A₂-A₃-A₄-CONH₂ (A₁-A₄ are amino acids) adopts a well-defined β-turn. The dihedral angles of A₂ and A₃ determine the type of β-turn.

Choose the combination of correct statements.

• A and B

• B and C

• A and D

• C and D

In the biosynthesis of purine:

• All N atoms, C4 and C5 are from aspartic acid.

• N1 is from aspartic acid; N3 and N9 are from glutamine side-chain; N7, C4 and C5 are from glycine.

• N1 is from aspartic acid; N3 from glutamine side-chain; N9 from N attached to C^α of glutamine; N7, C4, and C5 are from glycine.

• N1 is from glutamine; N3 from glutamine side-chain; N9 from attached to C^α of glutamine; N7, C4, and C5 are from glycine.

A researcher was investigating the substrate specificity of two different enzymes, X and Y, on the same substrate. Both the enzymes were subjected to treatment with either heat or an inhibitor of the enzyme activity. The following are the results obtained where a = inhibitor treatment, b = heat treatment, and c = control.

Which of the following statements is correct?

• Only protein X is specific for the substrate, S

• Only protein Y is specific for the substrate, S

• Both X and Y are specific for the substrate, S

• Both X and Y are non-specific for the substrate, S

Glycerol is added to protein solutions to stabilize the preparations by

• increasing the viscosity of solution

• stabilizing the pH

• preferential hydration of proteins

• interacting and neutralizing the surface charges on the proteins

Protein stability is represented as

Folded $\stackrel{{\mathrm{K}}_{\mathrm{eq}}}{\rightleftharpoons }$ Unfolded

Prior to the development of sensitive calorimeters, thermodynamic parameters of processes were determined by the following equation

ln K_eq = $\frac{-∆\mathrm{H}°}{\mathrm{R}}\left(\frac{1}{\mathrm{T}}\right) + \frac{∆\mathrm{S}°}{\mathrm{R}}$

$∆\mathrm{H}° \mathrm{and} ∆\mathrm{S}°$ are standard changes in enthalpy and entropy, respectively.

Which one of the following statements is correct for estimating $∆\mathrm{G}, ∆\mathrm{H} \mathrm{and} ∆\mathrm{S}$?

• Determining the ratio of folded and unfolded protein at 37°C.

• Plotting K_eq as a function of $∆$H

• Plotting K_eq against $∆$S

• Plotting K_eq against temperature

The pH of a solution is 7.4 ± 0.02 where 0.02 is the standard deviation obtained from eight measurements. If more measurements were carried out, the % samples whose pH would fall between pH 7.38 and 7.42 is

• 99.6

• 95.4

• 68.2

• 99.8

Which one of the following modification of proteins is co-translational?

• Palmitoylation

• Myristoylation

• Farnesylation

• Addition of cholesterol

From the following statements:

A. In proteins, the amino acids that can undergo oxidation are Cys and Met.

B. A tetrasaccharide composed of alternate L and D isomers will not be optically active.

C. The $∆$G(Kcal/ mol) values for K_eq of 0.1, 0.01 and 0.001 are 1.36, 2.72, and 4.09, respectively. It can be concluded that the relationship between $∆$G and K_eq is parabolic.

D. The oxidation states of Fe in haemoglobin is +2. In cytochrome C, the oxidation states of Fe can be +2 or +3.

E. In DNA, the sugar and bases are planar.

F. High-energy bonds hydrolyze with large negative $∆$G.

Choose the combination with only one wrong statement.

• A, E, F

• B, C, D

• C, D, E

• A, B, C

Point group symmetry operations such as inversion and mirror plane are not applicable to protein crystals. This is because

• protein molecules assemble in a highly ordered fashion.

• protein molecules have handedness

• protein molecules form a lattice plane that do not diffract X-rays.

• hydrogen atoms in proteins diffract weakly.