Carbohydrates that do not require fixation include which of the following?

• A. Chitin, starch, cellulose
• B. Glycogen
• C. Glucose
• D. Mannose

Answer: (A)

Understanding how fixation affects carbohydrate staining helps explain why some carbohydrates can be demonstrated without fixation. Some polysaccharides are highly resistant to fixation and dehydration reagents; they don’t dissolve out of the tissue during processing, so they can be preserved and visualized without a fixation step. Chitin (found in fungi and arthropod exoskeletons), starch (plant storage polysaccharide), and cellulose (plant cell walls) are examples of these robust, insoluble carbohydrates. Because they are not readily extracted by common fixatives, they can still be detected with appropriate stains even if no fixation is performed.

Glycogen, on the other hand, is water-soluble and readily lost during dehydration, making its demonstration depend on fixation and careful processing to preserve it. Monosaccharides like glucose and mannose are small and diffusible, so they’re not reliably demonstrated in tissue sections under standard histology conditions and are not considered carbohydrates that “do not require fixation” for visualization.

So, the best answer points to those carbohydrates that stay in place through routine processing: chitin, starch, and cellulose.