14.21

There are two common types of secondary structure of proteins:

(i) α–helix structure

(ii) β–pleated sheet structure

α–Helix structure

If the size of R-groups is quite large then the intramolecular bonds are formed between the C=O of one amino acid and the N-H group of the forth amino acid residue in the chain. This causes the polypeptide chain to coil up into a spiral structure called righ handed α-helix structure.

β -pleated sheet structure

In this conformation, the polypeptide chains lie side by side in a zig0zag manner with alternate R groups on the same side situated at fixed distances a

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14.21

There are two common types of secondary structure of proteins:

(i) α–helix structure

(ii) β–pleated sheet structure

α–Helix structure

If the size of R-groups is quite large then the intramolecular bonds are formed between the C=O of one amino acid and the N-H group of the forth amino acid residue in the chain. This causes the polypeptide chain to coil up into a spiral structure called righ handed α-helix structure.

β -pleated sheet structure

In this conformation, the polypeptide chains lie side by side in a zig0zag manner with alternate R groups on the same side situated at fixed distances apart. The two such neighbouring polypeptide chains are held together by interbounded to form a sheet. These sheets are then stacked one above the other like the pages of the book to form a 3-D structure. This structure resembles pleated folds of drapery and hence is called β–pleated sheet structure. The polypeptide chains can link together in parallel and anti- parallel sequence. Such sheet like structure can easily slip on each other. Proteins of this structure are soft.

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<p><strong>14.21</strong></p><div><p>There are two common types of secondary structure of proteins:</p><p><strong>(i)</strong> α–helix structure</p><p><strong>(ii)</strong> β–pleated sheet structure</p><h1>α–Helix structure</h1><p>If the size of R-groups is quite large then the intramolecular bonds are formed between the C=O of one amino acid and the N-H group of the forth amino acid residue in the chain. This causes the polypeptide chain to coil up into a spiral structure called righ handed α-helix structure.</p><div><div><picture><source srcset="https://images.shiksha.com/mediadata/images/articles/1686816624phpncgekU_480x360.jpeg" media="(max-width: 500px)"><img src="https://images.shiksha.com/mediadata/images/articles/1686816624phpncgekU.jpeg" alt="" width="112" height="188"></picture></div><div><h1>β -pleated sheet structure</h1><p>In this conformation, the polypeptide chains lie side by side in a zig0zag manner with alternate R groups on the same side situated at fixed distances apart. The two such neighbouring polypeptide chains are held together by interbounded to form a sheet. These sheets are then stacked one above the other like the pages of the book to form a 3-D structure. This structure resembles pleated folds of drapery and hence is called β–pleated sheet structure. The polypeptide chains can link together in parallel and anti- parallel sequence. Such sheet like structure can easily slip on each other. Proteins of this structure are soft.</p><div><div><picture><source srcset="https://images.shiksha.com/mediadata/images/articles/1686816663phpDDsiEh_480x360.jpeg" media="(max-width: 500px)"><img src="https://images.shiksha.com/mediadata/images/articles/1686816663phpDDsiEh.jpeg" alt="" width="187" height="149"></picture></div></div></div></div></div>

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