Which of the following is NOT a recognized role of vitamin C (ascorbic acid)?

Serving as a primary structural component of hemoglobin's heme porphyrin ring.

Acting as a cofactor for enzymes that synthesize collagen and aiding iron absorption from plant foods.

Functioning as a water-soluble antioxidant and supporting white blood cell production.

Being readily excreted when consumed in large supplemental amounts because it is not stored extensively.