Which of the Following is NOT a Tetrapyrrole

Question

Which of the following is NOT a tetrapyrrole?
A) cytochrome
B) chlorophyll
C) vitamin B12
D) tryptophan
E) hemoglobin

Accepted Answer

Tryptophan is an amino acid, not a tetrapyrrole. The other choices are all tetrapyrroles: cytochrome contains a heme group, which is a tetrapyrrole; chlorophyll contains a porphyrin ring, which is a tetrapyrrole; vitamin B12 contains a corrin ring, which is a modified tetrapyrrole; and hemoglobin contains heme groups as well.