The secondary structure of a protein refers to

fixed configuration of the polypeptide backbone
α–helical backbone
hydrophobic interactions
sequence of α–amino acids.

Solution

The secondary structure of a protein refers to the shape in which a long peptide chain can exist. There are two different conformations of the peptide linkage present in protein, these are α-helix and β-conformation. The α-helix always has a right handed arrangement. In β-conformationall peptide chains are stretched out to nearly maximum extension and then laid side by side and held together by intermolecular hydrogen bonds.The structure resembles the pleated folds of drapery and therefore is known as β-pleated sheet.

Which of the statements about “Denaturation” given below are correct ?
(A)Denaturation of proteins causes loss of secondary and tertiary structures of the protein.
(B)Denaturation leads to the conversion of double strand of DNA into single strand
(C)Denaturation affects primary structure which gets distorted Options :

(B) and (C)
(A) and (C)
(A) and (B)
(A), (B) and (C)

Solution

When the proteins are subjected to the action of heat,mineral acids or alkali, the water soluble form of globular protein changes to water insoluble fibrous protein. This is called denaturation of proteins. During denaturation secondary and tertiary structures of protein destroyed but primary structures remains intact.

Which one of the following statements is not true regarding(+) Lactose ?

On hydrolysis (+) Lactose gives equal amount of D(+)glucose and D(+) galactose.
(+) Lactose is a β-glycoside formed by the union of a molecule of D(+) glucose and a molecule of D(+)galactose.
(+) Lactose is a reducing sugar and does not exhibit mutarotation.
(+) Lactose, C₁₂H₂₂O₁₁ contains 8-OH groups.

Solution

Which one of the following does not exhibit the phenomenon of mutarotation ?

(+) – Sucrose
(+) – Lactose
(+) – Maltose
(–) – Fructose

Solution

Sucrose does not have free —CHO or CO group, hence it does not undergo mutarotation.

Which of the following hormones contains iodine?

Testosterone
Adrenaline
Thyroxine
Insulin

Solution

Which of the following statement is not correct ?

Amylopectin is a branched polymer of α - glucose.
Cellulose is a linear polymer of β-glucose
Glycogen is the food reserve of plants
All proteins are polymers of α - amino acids.

Solution

Glycogen is called animal starch and is found in all animal cells. It constitutes the reserve food material.

Double stranded DNA virus with 20,000 base pairs has nucleotides

20,000
10,000
666
40,000

The two forms of D-glucopyranose obtained from the solution of D-glucose are called

isomers
anomers
epimers
enantiomers

Solution

The two isomeric forms ( α –and β–) of D-glucopyronose differ in configuration only at C–1;hence these are called anomers.

The pair of compounds in which both the compounds give positive test with Tollen’s reagent is

glucose and sucrose
fructose and sucrose
acetophenone and hexanal
glucose and fructose

Solution

Glucose being an aldose responds to Tollen’s test while fructose, although a ketose, undergoes rearrangement in presence of basic medium (provided by Tollen’s reagent) to form glucose, which then responds to Tollen’s test.

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