Which of the following organic compounds is the main constituent of lecithin?

Lecithin, a small molecular weight organic compound found in living tissues, is an example of:

Ligases is a class of enzymes responsible for catalysing the linking together of two compounds. Which of the following bonds is not catalysed by it?

Match List-I with List-II. \begin{array}{|l|l|l|l|}\hline & List-I & & List-II \\\hline A. & Primary structure of protein & I. & Human haemoglobin \\\hline B. & Secondary structure of protein & II. & Disulphide bonds \\\hline C. & Tertiary structure of protein & III. & Polypeptide chain \\\hline D. & Quaternary structure of protein & IV. & Alpha helix and \beta sheet \\\hline\end{array} Choose the correct answer from the options given below :

The cofactor of the enzyme carboxypeptidase is:

Match List-I with List-II  Choose the correct answer from the options given below.