Periodic Acid Schiff's shows what?

• A. Neutral mucin and glycogen
• B. Collagen
• C. Hemosiderin
• D. Myelin

Answer: (A)

Periodic acid–Schiff staining highlights structures rich in carbohydrates. The reagent oxidizes vicinal diols in sugars to aldehydes, which then react with Schiff reagent to produce a magenta color. This makes neutral mucins and glycogen readily visible as pink to magenta areas in tissues. Because the stain targets carbohydrate groups, it does not specifically highlight proteins like collagen, iron-containing pigments like hemosiderin, or lipids in myelin. In short, PAS marks neutral mucin and glycogen best, which is why that choice is correct. If glycogen is present, its signal can be removed by diastase digestion, helping distinguish glycogen from other carbohydrate-containing substances.