CBSE 2023 · Region 4 · Set 1 · Q31 · 4 marks
Living systems are made up of various complex biomolecules like carbohydrates, proteins, nucleic acids, lipids, etc. Carbohydrates are optically active polyhydroxy aldehydes or ketones or molecules which provide such units on hydrolysis. They are broadly classified into three groups - monosaccharides, oligosaccharides and polysaccharides. Monosaccharides are held together by glycosidic linkages to form disaccharides like sucrose, maltose or polysaccharides like starch and cellulose. Another biomolecule : proteins are polymers of $\displaystyle \alpha$-amino acids which are linked by peptide bonds. Ten amino acids are called essential amino acids. Structure and shape of proteins can be studied at four different levels i.e. primary, secondary, tertiary and quaternary, each level being more complex than the previous one. Answer the following questions :(i)What is the difference between a glycosidic linkage and peptide linkage ?(ii)Which amino acids are called essential amino acids ?What are the common types of secondary structures of proteins ? Write any two forces which stabilise the secondary and tertiary structures of protein.Define denaturation of protein with an example. During denaturation which structures of protein lose their biological activity ?
Living systems are made up of various complex biomolecules like carbohydrates, proteins, nucleic acids, lipids, etc. Carbohydrates are optically active polyhydroxy aldehydes or ketones or molecules which provide such units on hydrolysis. They are broadly classified into three groups - monosaccharides, oligosaccharides and polysaccharides. Monosaccharides are held together by glycosidic linkages to form disaccharides like sucrose, maltose or polysaccharides like starch and cellulose. Another biomolecule : proteins are polymers of $\displaystyle \alpha$-amino acids which are linked by peptide bonds. Ten amino acids are called essential amino acids. Structure and shape of proteins can be studied at four different levels i.e. primary, secondary, tertiary and quaternary, each level being more complex than the previous one. Answer the following questions :
(i)
What is the difference between a glycosidic linkage and peptide linkage ?
(ii)
Which amino acids are called essential amino acids ?
What are the common types of secondary structures of proteins ? Write any two forces which stabilise the secondary and tertiary structures of protein.
Define denaturation of protein with an example. During denaturation which structures of protein lose their biological activity ?
Marking-scheme solution
(i)
Peptide linkage : A linkage formed when two amino acids are joined through - CONH - bond.
Glycosidic linkage: When two monosaccharides are joined through oxygen atom.
(ii)
Those which are not synthesised in the body and must be obtained through diet.
(iii)
\[\alpha \text {-helix and } \beta \text {-pleated sheet. }
\]
Hydrogen bond, van der Waals forces, disulphide linkages, electrostatic force of attraction.
BiomoleculesCarbohydratesUnderstandcase_studymedium
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CBSE Class 12 Chemistry past-paper question from the 2023board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.