Question

what is difference between plasma membrane and the outer membrane?

Answer 1

The plasma membrane is selectively permeable – it will allow some things to pass through, while blocking other things.
The bacterial outer membrane is found in Gram-negative bacteria. Its composition is distinct from that of the cytoplasmic membrane - among other things, the outer leaflet of the membrane includes a complex lipopolysaccharide whose lipid portion acts as an endotoxin - and it is linked to the cell's peptidoglycan by Braun's lipoprotein.The outer mitochondrial membrane, which encloses the entire organelle, has a protein-to-phospholipid ratio similar to the eukaryotic plasma membrane (about 1:1 by weight).

Answer 2

Plasma membrane is something that lines the cytoplasm and marks the outline of the cell. you can imagine cell as a house, then plasma membrane will be its walls. It separates intracellular environment from the extracellular environment and is semipermeable. That means it permits only selective substances to pass through it, this property helps in maintaining the intracellular environment very different from extracellualar one.

Some cells have two layers of such membrane, (NOTE : no cell in human body has double layer of membranes) one that lies inside and one that lies outside. The composition of both these membranes can differ according to the distinct job they perform. For example, bacterial outer membrane is rich in lipids, which offers bacterial cell some extra immunity from antibody attacks.