$99 \%$ of living systems are made up of four elements:

Complete the following analogy-type questions:
$(i)$ Purine : Guanine :: Pyrimidine : .........
$(ii)$ Hexokinase : Transferase :: Amylase : .........

Disorders of amino acid metabolism result in which of the following conditions?

Identify the statement which is incorrect.

The ready source of energy in living cells is

Hyperkeratosis is caused due to the excess of which vitamin?