Anatomy and Cell Biology 3309 Study Guide - Final Guide: Nuclear Membrane, Lipid Bilayer, Signal Peptidase
8 Dec 2011
School
Department
Professor
Document Summary
He staining is the most commonly used stain in histology. Fixation is the first step in the preparation of a tissue or organ sample: this is done by a chemical or a mixture of chemicals. It preserves tissue structure permanently through 4 methods: Prevents enzymatic degradation of cells and tissues by autolysis (self-digestion) Kills pathogenic bacteria, fungi, viruses (i. e. microorganisms) It hardens the tissue as a result of cross-linking or denaturing protein molecules. Formalin is often used as a fixative; it contains formaldehyde: this does not significantly alter the 3d structure of proteins. Therefore, proteins are still able to react with antibodies and other reagents. It does not react with lipids and therefore, is a poor fixative for cell membranes. The composition of tissue is altered after formalin-fixation; certain substances are lost: small nucleic acids, glycogen, proteoglycans and gags. Pas can be used for carbohydrate staining.
