Question 1

\alpha -D-glucose differs from  \beta -D-glucose due to difference in one of the carbon atoms with respect to its:

Accepted Answer

\alpha  glucose and  \beta  glucose are structurally identical except with the difference in the "configuration" of the anomeric carbon atom. So, they are also called as anomers.

Question 2

The anomeric carbon in  D(+)  glucose is:

Accepted Answer

The cyclic hemiacetal forms of glucose differ only in the configuration of the hydroxyl group at  C-1 , called anomeric carbon. Such isomers, i.e.,  \alpha \; \& \; \beta  form are called anomers.

Question 3

What type of glycoside linkage is the following?

Accepted Answer

The glycosidic linkage is  \beta\,(1\rightarrow4') .It the linkage present between first carbon of one monosaccharide and fourth carbon of second monosaccharide.

Question 4

In polysaccharides, the linkage connecting monosaccharides is called:

Accepted Answer

In polysaccharides, the linkage connecting monosaccharides is called glycoside (glycosidic linkage). Glycosidic linkage is the covalent bond between two or more monosaccharides to form a polysaccharide. It is formed between the hemiacetal or hemiketal group of a saccharide (or a molecule derived from a saccharide) and the hydroxyl group of some compound such as alcohol. A substance containing a glycosidic bond is a glycoside.

Question 5

Regarding secondary structure of a protein, correct statement(s) is/areA) Peptide bonds possess regional planarity.B)  C=O  and  -NH  of different peptide chains are held by Van der Waal's attractions.C) They have closely packed arrangement so as to minimise repulsion between R groups.

Accepted Answer

Peptide bonds possess regional planarity. For the entire molecule, the long amino acid chains exists in looped, coiled, stretched or folded structure.Thus, the statement A is correct. C=O  and  -NH  of different peptide chains are held by intermolecular hydrogen bonds.Thus, the statement B is incorrect.Closely packed arrangement is due to hydrogen bonds.Thus, the statement C is incorrect.Option D is correct.

Question 6

The secondary structure of a protein refers to:

Accepted Answer

The secondary structure of a protein refers to helical backbone. Secondary structure refers to the spatial arrangement of amino acid residues that are nearby in the sequence. Some of these arrangements are of a regular kind, giving rise to a periodic structure. The  \alpha  helix and  \beta  strand are elements of secondary structure. The secondary structure arises due to the regular folding of the backbone of the polypeptide chain due to intramolecular hydrogen bonding between the carboxyl and amino group.

Question 7

What does a protein lose when it denatures?

Accepted Answer

Protein which is affected by high temperature gets denatured which loses its three-dimensional structure and adverse its functions by changing its shapes. The primary structure or the sequence of amino acids are bonded by peptide bonds which do not get easily broken but the other bonds such as hydrogen bonds, disulphide bonds, etc get denatured thus affecting its shape and function. Hence, the correct answer is 'Its three-dimensional shape'.

Question 8

In aqueous solutions, amino acids mostly exist as:

Accepted Answer

In aqueous solutions, amino acids mostly exist as  H_{3}N^{+}-CHR-COO^{-}  (zwitter ion).Option D is correct.

Question 9

The pH value of a solution in which a polar amino acid does not migrate under the influence of electric field is called:

Accepted Answer

The  pH  value of a solution in which a polar amino acid does not migrate under the influence of electric field is called isoelectric point. This means it is the  pH  at which the amino acid is neutral, i.e., the zwitterion form is dominant.

Biomolecules