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Which of the following is correct regarding cell envelope?
Option: 1
Cell envelope consists of cell wall and cell membrane
Option: 2
Innermost layer of cell envelope is metabolically active
Option: 3
Glycocalyx mainly consists of polysaccharides
Option: 4
Both b and c
Answers (1)
Cell Envelope -
The outer covering of protoplasm of the bacterial cell is called the cell envelope. It includes 3 parts i.e glycocalyx, cell wall and cell membrane.
Glycocalyx-
- Outermost mucilage layer of cell envelope that consists of non-cellulosic polysaccharide with or without proteins.
- If glycocalyx is loose and smooth, it is called the slime layer however if it is thick and tough, it is called a capsule.
- Glycocalyx helps in the prevention of desiccation, protection from phagocytes, toxic chemicals, drugs and viruses. It is also involved in attachment, immunogenicity and virulence.
Cell wall-
- Rigid solid covering present between plasma membrane and glycocalyx.
- The cell wall is made up of peptidoglycan.
- Peptidoglycan is a polysaccharide made of two glucose derivatives N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM), alternated in long chains.
- On the basis of the structure of the cell wall, bacteria can be Gram positive or Gram negative
- The cell wall provides structural support to the cell, maintaining the shape of the cell and it also protects the cell.
Plasma membrane-
- The innermost layer of the cell envelope. It is selectively permeable i.e. allows the transfer of few molecules only.
- It is made up of phospholipid bilayer. Chemically, the bacterial cell membrane is similar to the eukaryotic cell membrane.
- The bacterial membrane is metabolically active and has a role in respiration and synthesis of lipids and cell wall components.
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