What is the difference between gram positive and gram negative cell wall?

Answer 1

there is only difference in gram positive and negative is of cell wall as :

The Gram positive cell wall

The Gram positive cell wall is characterised by the presence of a very thick peptidoglycan layer, which is responsible for the retention of the crystal violet dyes during the Gram staining procedure. It is found exclusively in organisms belonging to the Actinobacteria (or high %G+C Gram positive organisms) and the Firmicutes (or low %G+C Gram positive organisms). Bacteria within the Deinococcus-Thermus group may also exhibit Gram positive staining behaviour but contain some cell wall structures typical of Gram negative organisms. Imbedded in the Gram positive cell wall are polyalcohols called teichoic acids, some of which are lipid-linked to form lipoteichoic acids. Because lipoteichoic acids are covalently linked to lipids within the cytoplasmic membrane they are responsible for linking the peptidoglycan to the cytoplasmic membrane. Teichoic acids give the Gram positive cell wall an overall negative charge due to the presence of phosphodiester bonds between teichoic acid monomers.

The Gram negative cell wall

Unlike the Gram positive cell wall, the Gram negative cell wall contains a thin peptidoglycan layer adjacent to the cytoplasmic membrane, which is responsible for the cell wall's inability to retain the crystal violet stain upon decolourisation with ethanol during Gram staining. In addition to the peptidoglycan layer the Gram negative cell wall also contains an additional outer membrane composed by phospholipids and lipopolysaccharides which face into the external environment. The highly charged nature of lipopolysaccharides confer an overall negative charge to the Gram negative cell wall. The chemical structure of the outer membrane lipopolysaccharides is often unique to specific bacterial strains (i.e. sub-species) and is responsible for many of the antigenic properties of these strains.

As a phospholipid bilayer, the lipid portion of the outer membrane is largely impermeable to all charged molecules. However, channels called porins are present in the outer membrane that allow for passive transport of many ions, sugars and amino acids across the outer membrane. These molecules are therefore present in the periplasm, the region between the plasma membrane and outer membrane. The periplasm contains the peptidoglycan layer and many proteins responsible for substrate binding or hydrolysis and reception of extracellular signals. The periplasm is thought to exist as a gel-like state rather than a liquid due to the high concentration of proteins and peptidoglycan found within it. Because of its location between the cytoplasmic and outer membranes, signals received and substrates bound are available to be transported across the cytoplasmic membrane using transport and signalling proteins imbedded there.

Answer 2

alright the main difference between gram + and gram - is gram + have a plasma membrane that is surrounded by a cell wall that is made up of a thick layer ofpeptidoglycan (which is made up of polysaccarrides chains). This also applies to gram - but the amount of peptidoglycan is much less. another important difference is that gram - have a outer membrane surrounding the layer of peptidoglycan.

Answer 3

The key difference between the two is that Gram + cell membranes contain large amounts of peptidoglycan, whereas Gram - cell membranes contain a drastically lesser amount of peptidoglycan. This is why in a Gram stain a Gram + membrane appears a dark blue/violet color because it retains much more of the dye relative to a Gram - membrane which appears pink due to less dye retention.

Answer 4

Gram-positive cell walls have a thick layer of peptidoglycan outside the cell membrane, while gram-negative cell walls have a thin layer of peptidoglycan sandwiched between two cell membranes. Gram-positive bacteria stain purple in the Gram stain test, while gram-negative bacteria stain pink. Gram-negative cell walls also contain lipopolysaccharides, which are absent in gram-positive cell walls.