Question

Describe the structure of the cell envelope of a gram-positive bacteria and compare it with that of a gram-negative bacteria. Give detailed answer.

Answer 1

Answer=

Structure of the cell envelope of a gram-positive bacteria =

The cell envelope comprises the inner cell membrane & cell wall of a bacterium.

The cell envelope of gram positive bacteria ,outer membrane is absent.

gram positive cell wall= there is thicker layers of peptidoglycan ,threading through these layers of peptidoglycan are long anionic polymers,called teichoic acids,which are composed of largely glycerol phosphate,glucosyl phosphate or ribitol phosphate repeats.

teichoic acids give the gram gram positive cell wall an overall negative charge due to the presence of phosphodiester bonds between teichoic acid monomers.

in addition to techoic acid the surfaces consists of variety of proteins,

outside the cell wall,many gram positive bacteria have an S-layerof tiled proteins.

This layer assists attachment & biofilm formation.

outside the S-layer there is often a capsule of polysaccharides.

Difference in cell envelope of gram positive & gram negative bacteria=

cell envelope of gram positive bacteria	cell envelope of gram negative bacteria
1.consists of only cell wall ,outer membrane is absent.	1.consists of outer membrane.
2.A Thick layer of peptidoglycan is present	2.A Thin layer of peptidoglycan is present
3.The surfaces of gram positive bacteria contains variety of proteins	3.contains periplasm.
4.techoic acid is present	4.Techoic acid is absent.