Q: The iron ion used to bind oxygen is on what type of "ring"?


Read this paragraph and choose the correct option from the provided answers:

The yellow subunits are identical in structure, as are the gray subunits. A smaller organic structure called a porphyrin ring is attached to each protein subunit and contains the iron ion used to bind oxygen.

 Choices:

- DNA ring

- petrarchan ring

- reagent ring

- porphyrin ring


A:
porphyrin ring