Question

What do two sugar isomers have in common?

Answer 1

The same molecular formula.

Explanation:

Isomers are compounds which share a molecular formula but have different structures. E.g., glucose and fructose are both `C_6H_12O_6`, but have different structures.

As you can see here, glucose contains a 5 carbon ring and only one hydroxymethyl group (`CH_2OH`), whereas fructose contains a 4 carbon ring and two hydroxymethyl groups. They do, however, contain the same number of each type of atom and are able to be converted to each other by isomerase enzymes.