In haemoglobin,iron is present in:

Refer to the given structure of adenylic acid. In this,identify $A$.

Which property of water allows it to absorb or lose heat from the surrounding environment without undergoing a significant change in its temperature?

Which one of the following biomolecules is correctly characterized?

Match the following columns:

Column $I$	Column $II$
$(A)$ $NAD$	$(i)$ Nicotinamide Adenine Dinucleotide Phosphate
$(B)$ $NADP$	$(ii)$ Flavin Mononucleotide
$(C)$ $FAD$	$(iii)$ Nicotinamide Adenine Dinucleotide
$(D)$ $FMN$	$(iv)$ Flavin Adenine Dinucleotide

The figure given below shows three velocity-substrate concentration curves for an enzyme reaction. What do the curves $a, b$ and $c$ depict respectively?