Biology Class 11 NCERT Solutions: Chapter 9 Biomolecules Part 1

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Q: 1. What are macromolecules? Give examples.


Macromolecules are large complex molecules that occur in colloidal state in intercellular fluid. They are formed by the polymerization of low molecular weight micromolecules. Polysaccharides, proteins, and nucleic acids are common examples of macromolecules.

Image of examples of macromolecules

Image of Examples of Macromolecules

Q: 2. Illustrate a glycosidic, peptide and a phosphodiester bond.


(A) Glycosidic bond is formed normally between carbon atoms, and , of neighbouring monosaccharide units.

Glycosidic bond

Glycosidic Bond

(B) Peptide bond is a covalent bond that joins the two amino acids by linkage

Peptide bond

Peptide Bond

(C) Phosphodiester bond is a strong covalent bond between phosphate and two sugar groups. Such bonds form the sugar phosphate backbone of nucleic acids.

Structure of phosphodiester

Structure of Phosphodiester

Q: 3. What is meant by tertiary structure of proteins?


The helical polypeptide chain undergoes coiling and folding to form a complex three-dimensional shape referred to as tertiary structure of proteins. These coils and folds are arranged to hide the non-polar amino acid chains and to expose the polar side chains. The tertiary structure is held together by the weak bonds formed between various parts of the polypeptide chain.

Image of tertiary structure of proteins

Image of Tertiary Structure of Proteins

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