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

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?

Structures of glycine and alanine are given below. Show the peptide linkage in glycylalanine.

\[\ce{\underset{(Glycine)}{H2N - CH2 - COOH}}\]; 

\[\begin{array}{cc}
\ce{H2N - CH2 - COOH}\\
|\phantom{......}\\
\ce{\underset{(Alanine)}{CH3}\phantom{...}}
\end{array}\]

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?

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

Assertion (A): Proteins are found to have two different types of secondary structures viz alpha-helix and beta-pleated sheet structure.

Reason (R): The secondary structure of proteins is stabilized by hydrogen bonding.

Select the most appropriate answer from the options given below:

Read the passage carefully and answer the questions that follow:

Assuming the melting point of pure water as 0°C, answer the following questions:

1. One temperature in the second set of results does not fit the pattern. Which temperature is that? Justify your answer.
2. Why did Henna collect two sets of results?
3. In place of NaCl, if Henna had used glucose, what would have been the melting point of the solution with 0.6 g glucose in it?
   OR
   What is the predicted melting point if 1.2 g of salt is added to 10 mL of water? Justify your answer.

Differentiate between the following:

Lyophobic Sol and Lyophilic Sol

An α-helix is a structural feature of ______.

Proteins are polymers of ______.

Which of the following cell was used in the Apollo space programme?

Assertion (A): Proteins are polymers of α-amino acids connected by a peptide bond.

Reason (R): A tetrapeptide contains 4 amino acids linked by 4 peptide bonds.

When 25.6 g of sulphur was dissolved in 1000 g of benzene, the freezing point lowered by 0.512 K. Calculate the formula of sulphur (Sr).

(K_f for benzene = 5.12 K kg mol⁻¹, Atomic mass of sulphur = 32 g mol⁻¹)

Write the equation for the following:

Reaction of chlorobenzene with CH₃Cl/anhyd. AlCl₃.