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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
Define the following as related to proteins:
Peptide linkage
What type of bonding helps in stabilising the α-helix structure of proteins?
Differentiate between the following:
Fibrous proteins and Globular proteins
Write one difference between α-helix and β-pleated structures of proteins.
The protein responsible for blood clotting is ____________.
Which functional group participates in disulphide bond formation in proteins?
Which of the following statement is correct:
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
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.
Explain formation of peptide linkage in protein with an example.
Given below are two statements labelled as Assertion (A) and Reason (R).
Assertion (A): Proteins are found to have two different types of secondary structures viz alpha-helix and beta-pleated sheet structure.
Reason (R): The secondary structure of proteins is stabilized by hydrogen bonding.
Select the most appropriate answer from the options given below:
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)
An α-helix is a structural feature 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.
β-pleated sheet structure in proteins refers to ______.
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:
