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प्रश्न
Differentiate between the following:
Fibrous proteins and Globular proteins
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उत्तर १
| Fibrous protein | Globular protein |
| It is a fibre-like structure formed by the polypeptide chain. These proteins are held together by strong hydrogen and disulphide bonds. | The polypeptide chain in this protein is folded around itself, giving rise to a spherical structure. |
| It is usually insoluble in water. | It is usually soluble in water. |
| Fibrous proteins are usually used for structural purposes. For example, keratin is present in nails and hair; collagen in tendons; and myosin in muscles. | All enzymes are globular proteins. Some hormones such as insulin are also globular proteins. |
उत्तर २
Fibrous proteins: These proteins consist of linear thread like molecules which tend to lie side by side (parallel) to form fibres. The polypeptide chains in them are held together usually at many points by hydrogen bonds and some disulphide bonds. As a result,intermolecular forces of attraction are very’ strong and hence fibrous proteins are insoluble in water. Further, these proteins are stable to moderate changes in temperature and pH. Fibrous proteins serve as the chief structural material of animal tissues.For example, keratin in skin, hair, nails and wool, collagen in tendons, fibrosis in silk and myosin in muscles.
Globular proteins: The polypeptide chain in these proteins is folded around itself in such a way so as to give the entire protein molecule an almost spheroidal shape. The folding takes place in such a manner that hydrophobic (non-polar) parts are pushed inwards and hydrophilic (polar) parts are pushed outwards. As a result, water molecules interact strongly with the polar groups and hence globular protein are water soluble. As compared to fibrous proteins, these are very sensitive to small changes of temperature and pH. This class of proteins include all enzymes, many hormones such as insulin from pancreas, thyroglobulin from thyroid gland, etc.
संबंधित प्रश्न
What type of bonding helps in stabilising the α-helix structure of proteins?
Write one difference between α-helix and β-pleated structures of proteins.
Differentiate between the following :
Peptide linkage and Glycosidic linkage
Proteins are found to have two different types of secondary structures viz. α-helix and β-pleated sheet structure. α-helix structure of protein is stabilised by:
Optical rotations of some compounds along with their structures are given below which of them have D configuration.
| (I) |  |
| (II) |  |
| (III) |  |
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?
Explain the terms primary and secondary structure of proteins. What is the difference between α-helix and β-pleated sheet structure of proteins?
Explain formation of peptide linkage in protein with an example.
Presence of disulphide link gives rise to which structure of protein?
The correct structure of Ruhemann's Purple, the compound formed in the reaction of ninhydrin with proteins is:
An α-helix is a structural feature of ______.
β-pleated sheet structure in proteins refers to ______.
What is the effect of denaturation on the structure of proteins?
Write a classification of proteins with an example.
