Calciferol is

The figure shows a hypothetical tetrapeptide portion of a protein with parts labelled $a$ to $d$. Which one of the following options is correct?

The common immediate source of energy in cellular activity or the energy currency of the cell is:

Mineral elements $C, H, O$ and $N$ are found in the structure of which of the following?

$A$ diet rich in butter,red meat,and eggs,when consumed regularly,will lead to:

In which component is a heterocyclic ring found?