Science (English Medium) Class 12 - CBSE Question Bank Solutions

Proteins are found to have two different types of secondary structures viz. α-helix and β-pleated sheet structure. α-helix structure of protein is stabilised by:

Dinucleotide is obtained by joining two nucleotides together by phosphodiester linkage. Between which carbon atoms of pentose sugars of nucleotides are these linkages present?

Optical rotations of some compounds along with their structures are given below which of them have D configuration.

(I)
(II)
(III)

Proteins can be classified into two types on the basis of their molecular shape i.e., fibrous proteins and globular proteins. Examples of globular proteins are:

(i) Insulin

(ii) Keratin

(iii) Albumin

(iv) Myosin

In fibrous proteins, polypeptide chains are held together by:

(i) van der Waals forces

(ii) disulphide linkage

(iii) electrostatic forces of attraction

(iv) hydrogen bonds

Which of the following are purine bases?

(i) Guanine

(ii) Adenine

(iii) Thymine

(iv) Uracil

α-Helix is a secondary structure of proteins formed by twisting of polypeptide chain into right-handed screw like structures. Which type of interactions are responsible for making the α-helix structure stable?

Protein found in a biological system with a unique three-dimensional structure and biological activity is called a native protein. When a protein in its native form, is subjected to a physical change like change in temperature or a chemical change like, change in pH, denaturation of protein takes place. Explain the cause.

Which moieties of nucleosides are involved in the formation of phosphodiester linkages present in dinucleotides? What does the word diester in the name of linkage indicate? Which acid is involved in the formation of this linkage?

Assertion: β-glycosidic linkage is present in maltose,

Reason: Maltose is composed of two glucose units in which C–1 of one glucose unit is linked to C–4 of another glucose unit.

Explain the terms primary and secondary structure of proteins. What is the difference between α-helix and β-pleated sheet structure of proteins?

Which of the following is not a semisynthetic polymer?

The commercial name of polyacrylonitrile is ______.

Which of the following polymers, need atleast one diene monomer for their preparation?

(i) Dacron

(ii) Buna-S

(iii) Neoprene

(iv) Novolac

Name the polymers used in laminated sheets and give the name of monomeric units involved in its formation.

Match the polymers given in Column I with the type of linkage present in them given in Column II.

Match the polymers given in Column I with their repeating units given in Column II.

Column I	Column II
(i) Acrilan	(a) \[\begin{array}{cc} \ce{-(CH2 - CH)\underset{n}{-}}\\ \phantom{....}|\\ \phantom{.......}\ce{C6H5} \end{array}\]
(ii) Polystyrene	(b) \[\begin{array}{cc} \ce{Cl}\phantom{.......}\\ |\phantom{........}\\ \phantom{}\ce{-(CH2 - C = CH - CH2)\underset{n}{-}} \end{array}\]
(iii) Neoprene	(c) \[\begin{array}{cc} \phantom{................................}\ce{CN}\\ \phantom{..............................}|\\ \ce{-(CH2 - CH = CH - CH2 - CH2 - CH)\underset{n}{-}} \end{array}\]
(iv) Novolac	(d) \[\begin{array}{cc} \ce{-(CH2 - CH)\underset{n}{-}}\\ \phantom{.....}|\\ \phantom{.......}\ce{CN} \end{array}\]
(v) Buna—N	(e)
	(f)  \[\begin{array}{cc} \ce{-(CH2 - CH)\underset{n}{-}}\\ \phantom{.....}|\\ \phantom{......}\ce{Cl} \end{array}\]

Phenol and formaldehyde undergo condensation to give a polymar (A) which on heating with formaldehyde gives a thermosetting polymer (B). Name the polymers. Write the reactions involved in the formation of (A). What is the structural difference between two polymers?

Convert the following:

Chloroethane to methanamine.

Given below are two statements labelled as Assertion (A) and Reason (R).

Assertion (A): An ether is more volatile than an alcohol of comparable molecular mass

Reason (R): Ethers are polar in nature.

Select the most appropriate answer from the options given below: