Membrana celular

Proteínas de la membrana

Modelo de mosaico fluido

citoplasma

mitocondria

http://www.cat.cc.md.us/courses/bio141/lecguide/unit1/prostruct/u1fig11.html

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.

PropertyGram Positive

Gram Negative

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 content

0-3% 58%

Protein content 0% 9%

Lipopolysaccharide 0 13%

Sensitive to penicliiin + - (not as)

Digested by lysozyme + - (not as much

Propiedades de pared celular