NCERT Class 11-Biology Exemplar Chapter – 9 Biomolecules Part 3 (For CBSE, ICSE, IAS, NET, NRA 2022)

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Question 2:

Select an appropriate chemical bond among ester bond, glycosidic bond, peptide bond and hydrogen bond and write against each of the following.

a. Polysaccharide ________

b. Protein ________

c. Fat ________

d. Water ________


A. Polysaccharides – Glycosidic bond, formed by elimination of water molecule.

B. Protein- peptide bond, it is the -CO-NH- BOND formed by elimination of water molecules.

C. Fats- ester bond, derived from an acid (organic or inorganic) in which at least one – OH (hydroxyl) group is replaced by an – O – alkyl (alkoxy) group

D. Water- H-bond, formed between hydrogen of one water molecule and oxygen of the other water molecule.

Question 3:

Write the name of any one aminoacid, sugar, nucleotide and fatty acid.


  • Amino acid- Glycine
  • Sugar- Glucose
  • Nucleotide- Adenosine
  • Fatty acid- Oleic acid

Question 4:

Reaction given below is catalysed by oxidoreductase between two substrates A and A ′ , complete the reaction.


Question 5:

How are prosthetic groups different from co-factors?


  • Cofactors are the no proteineous, may be organic or inorganic constituent of enzyme.
  • Prosthetic group belongs to organic co factors, remains tightly binded with apoenzymes.

Question 6:

Glycine and Alanine are different with respect to one substituent on the carbon. What are the other common substituent groups?


, and are the common substituents.

Question 7:

Starch, Cellulose, Glycogen, Chitin are polysaccharides found among the following. Choose the one appropriate and write against each.

Cotton fibre ________

Exoskeleton of cockroach ________

Liver ________

Peeled potato ________


Cotton fibre- cellulose [more than 90 %]

Exoskeleton of cockroach- chitin

Liver- glycogen

Peeled potato- starch

Short Answer Type Questions

Question 1:

Enzymes are proteins. Proteins are long chains of aminoacids linked to each other by peptide bonds. Aminoacids have many functional groups in their structure. These functional groups are, many of them at least, ionisable. As they are weak acids and bases in chemical nature, this ionization is influenced by pH of the solution. For many enzymes, activity is influenced by surrounding . This is depicted in the curve below, explain briefly.


Chapter 9 - Question 1 Enzymes Are Proteins
  • Enzymes show highest activity at an optimum .
  • The dependence of enzyme on pH is due to the presence of charged amino acid at its active site, variation causes changes in charge of amino acid.
  • Hence, in both the cases either when the pH is less than the optimum pH or greater than it, enzymatic activity decreases.
  • Therefore, we get a bell shaped curve of enzymatic activity against .