Biomolecules

Identify the incorrect statement about tertiary structure of proteins.

1. They can be fibrous or globular in structure.
2. The main forces that stabilize the structure are hydrogen bonding, disulphide links, van der Waals and electrostatic forces of attraction.
3. The structure remains intact when exposed to pH changes.
4. A linear polypeptide chain will convert to a secondary structure and then further folding of the secondary structure will convert to tertiary structure.

In the given pentapeptide, find out an essential amino acid (Y) and the sequence present in the pentapeptide : [figure] Choose the correct answer from the options given below :

1. arrayll(Y) & (Sequence) \ Serine & Thr-Ser-Asp-Ala-Gly array
2. arrayll(Y) & (Sequence) \ Serine & Ser-Asp-Thr-Ala-Gly array
3. arrayll(Y) & (Sequence) \ Threonine & Ser-Thr-Asp-Gly-Ala array
4. arrayll(Y) & (Sequence) \ Threonine & Thr-Ser-Asp-Gly-Ala array

The number of possible tripeptides formed involving alanine (ala), glycine (gly) and valine (val), where no amino acid has been used more than once is:

1. 8
2. 3
3. 4
4. 6

The correct statements are : Choose the correct answer from the options given below :

1. A, B and D Only
2. A, C and D Only
3. B and C Only
4. A and B Only

Given below are two statements : In the light of the above statements, choose the most appropriate answer from the options given below :

1. Statement I is incorrect but Statement II is correct
2. Both Statement I and Statement II are incorrect
3. Both Statement I and Statement II are correct
4. Statement I is correct but Statement II is incorrect

Identify the pair of reactants that upon reaction, with elimination of HCl will give rise to the dipeptide Gly-Ala.

1. NH2-CH2-COOH and NH2- CH3 |CH-COOH
2. NH2-CH2-COCl and NH3- CH3 |CH-COCl
3. NH2-CH2-COCl and NH2- CH3 |CH-COOH
4. NH2-CH2-COOH and NH2- CH3 |CH-COCl

A dipeptide, "x" on complete hydrolysis gives "y" and "z". "y" on treatment with aq. HNO2 produces lactic acid. On the other hand "z" on heating gives the following cyclic molecule. [figure] Based on the information given, the dipeptide "x" is :

1. alanine-alanine
2. valine-glycine
3. valine-leucine
4. alanine-glycine

A tetrapeptide, "x" on complete hydrolysis produced glycine (Gly), alanine (Ala), valine (Val), leucine (Leu) in equimolar proportion each. The number of tetrapeptides (sequences) possible involving each of these amino acids is:

1. 32
2. 24
3. 8
4. 16