Fixatives · Pathology

What is the primary mechanism of action of formaldehyde as a fixative?

  1. Osmotic dehydration of cellular proteins
  2. Cross-linking proteins via methylene bridges
  3. Coagulation of cytoplasmic protein networks
  4. Chemical precipitation of nucleic acids
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Correct answer: Cross-linking proteins via methylene bridges

Formaldehyde is an additive, non-coagulant fixative that reacts primarily with basic amino acids to form methylene bridges (cross-links). This preserves the relationship between proteins and maintains the structural integrity of the tissue.

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