The porphyrin test determines an organism's requirement for which growth factor?

The porphyrin test determines an organism's requirement for which growth factor?

• A. Cystiene
• B. Hemin
• C. NAD
• D. Thiol

Answer: (B)

The test assesses whether an organism can synthesize porphyrin (heme) on its own or must obtain it from the environment, which reveals its need for a growth factor called hemin (X factor). If the organism can make porphyrin when provided with a precursor like δ-aminolevulinic acid, it can grow without exogenous hemin; if it cannot, it requires hemin to grow. This is why the growth factor being determined is hemin. The other options relate to different nutrient requirements and are not what this test evaluates.

The test assesses whether an organism can synthesize porphyrin (heme) on its own or must obtain it from the environment, which reveals its need for a growth factor called hemin (X factor). If the organism can make porphyrin when provided with a precursor like δ-aminolevulinic acid, it can grow without exogenous hemin; if it cannot, it requires hemin to grow. This is why the growth factor being determined is hemin. The other options relate to different nutrient requirements and are not what this test evaluates.