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प्रश्न
Discuss the optical activity of lactic acid.
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उत्तर
(1) Lactic acid contains one asymmetric carbon atom which is attached to four different groups, COOH, CH3, OH and H.
(2) Two different arrangements of these groups around the carbon atom are possible as shown in the figure. Hence, it exist as a pair of enantiomers. The two enantiomers are mirror images of each other and are non-superimposable.
(3) Hence, lactic acid can exist in two different forms, d-Form and l-form, which are non-superimposable mirror images of each other. d-form rotates the plane of plane-polarized light to the right, while l-form rotates the same to the left.
(4) A mixture containing equimolar amounts of the d- and l-forms is a racemic mixture which is optically inactive (dl - form). This inactivity arises due to external compensation.
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संबंधित प्रश्न
How is tripeptide formed?
Define the following as related to proteins:
Peptide linkage
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Fibrous proteins and Globular proteins
Write one difference between α-helix and β-pleated structures of proteins.
Which of the following statement is correct:
Dinucleotide is obtained by joining two nucleotides together by phosphodiester linkage. Between which carbon atoms of pentose sugars of nucleotides are these linkages present?
Optical rotations of some compounds along with their structures are given below which of them have D configuration.
| (I) |  |
| (II) |  |
| (III) |  |
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(i) Insulin
(ii) Keratin
(iii) Albumin
(iv) Myosin
Which of the following are purine bases?
(i) Guanine
(ii) Adenine
(iii) Thymine
(iv) Uracil
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?
The main structural feature of proteins is
Peptide linkage is:
Explain formation of peptide linkage in protein with an example.
Presence of disulphide link gives rise to which structure of protein?
Out of the following, which type of interaction is responsible for the stabilisation of the α-helix structure of proteins?
The total number of negative charge in the tetrapeptide, Gly-Glu-Asp-Tyr at pH 12.5 will be ______. (Integer answers)
Proteins are polymers of ______.
Assertion (A): Proteins are polymers of α-amino acids connected by a peptide bond.
Reason (R): A tetrapeptide contains 4 amino acids linked by 4 peptide bonds.
What is the effect of denaturation on the structure of proteins?
Write a classification of proteins with an example.
Match List I with List II:
| List I | List II |
| A. GLUT-4 | I. Hormone |
| B. Insulin | II. Enzyme |
| C. Trypsin | III. Intercellular ground substance |
| D. Collagen | IV. Enables glucose transport into cells |
Choose the correct answer from the options given below:
Statement I: A protein is imagined as a line, the left end represented by first amino acid (C-terminal) and the right end represented by last amino acid (Nterminal).
Statement II: Adult human haemoglobin, consists of 4 subunits (two subunits of a type and two subunits β type.)
In the light of the above statements, choose the correct answer from the options given below:
