2. Membrana celular

4. Proteínas de la membrana

5. Modelo de mosaico fluido

7. citoplasma
mitocondria

16. Acid Reflux: The Acid-Fast Cell Wall
The acid-fast cell wall is the black sheep of the group of cell walls. It does not contain a large
peptidoglycan content, separating it from Gram+ Cell Walls, but it also does not feature an outer
layer like Gram- Cell Walls. Around 60% of the cell wall is composed of a waxy lipid called mycolic
acid. (3) This mycolic acid, plus other glycolipids, such as aribanogalactan, can inhibit and regulate
the passage of certain chemicals across the cell wall, thus giving the cell a stronger resistance to
chemical and immunological destruction. This also renders the cell impenetrable by the stains used
in Gram staining. Special staining techniques have been developed for Acid-Fast Cell Walls, called
Acid-Fast Stains. Carbol fuchsin is used as a dye to bind to the mycolic acid. It is allowed to
penetrate into the cell wall by either application of moist heat or detergent. Once combined with
mycolic acid, the carbol fuchsin remains fast to the cell wall. An acidified solution of alcohol is used
as a decolorizer, and will remove the carbol fuchsin from any non acid-fast cell walls.

17. Propiedades de pared celular
Gram
Property Gram Negative
Positive
Thickness of wall 20-80 nm 10 nm
Number of layers in wall 1 2
Peptidoglycan content >50% 10-20%
Teichoic acid in wall + -
Lipid and lipoprotein
0-3% 58%
content
Protein content 0% 9%
Lipopolysaccharide 0 13%
Sensitive to penicliiin + - (not as)
Digested by lysozyme + - (not as much