Advertisements
Advertisements
Question
Discuss the optical activity of lactic acid.
Advertisements
Solution
(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.
APPEARS IN
RELATED QUESTIONS
How are proteins classified on the basis of molecular shapes?
What is peptide linkage?
What are the common types of secondary structure of proteins?
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.
Differentiate between the following :
Peptide linkage and Glycosidic linkage
Which of the following biomolecules is insoluble in water?
The helical structure of protein is stabilized by:
Which functional group participates in disulphide bond formation in proteins?
Which of the following statement is correct:
In fibrous proteins, polypeptide chains are held together by:
(i) van der Waals forces
(ii) disulphide linkage
(iii) electrostatic forces of attraction
(iv) hydrogen bonds
Which of the following are purine bases?
(i) Guanine
(ii) Adenine
(iii) Thymine
(iv) Uracil
Assertion: β-glycosidic linkage is present in maltose,
Reason: Maltose is composed of two glucose units in which C–1 of one glucose unit is linked to C–4 of another glucose unit.
Explain the terms primary and secondary structure of proteins. What is the difference between α-helix and β-pleated sheet structure of proteins?
The main structural feature of proteins is
Each polypeptide in a protein has amino acids linked with each other in a specific sequence. This sequence of amino acids is said to be ______.
Peptide linkage is:
Explain formation of peptide linkage in protein with an example.
Presence of disulphide link gives rise to which structure of protein?
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 ______.
Proteins are polymers of ______.
β-pleated sheet structure in proteins refers to ______.
