Biology · Cell: The Unit of Life · NEET
From the outside going inward: (1) Glycocalyx, (2) Cell wall, (3) Plasma membrane. NCERT calls this a 'chemically complex' envelope where the layers act as a single protective unit. A simple trick: the outermost layer is the stickiest (glycocalyx), the middle gives shape (cell wall), and the innermost controls what enters (plasma membrane). Getting this order right matters because NEET often asks 'which layer is outermost/innermost'.
The glycocalyx. It is the outermost layer and makes the bacterium sticky, which helps it attach to surfaces. The cell wall gives shape and support, and the plasma membrane is selectively permeable, so neither of those is sticky. This exact point was asked in NEET 2017, and the answer was glycocalyx.
Both are forms of the glycocalyx (the outer layer). A SLIME layer is a loose, thin sheath that is easily washed off. A CAPSULE is a thick, tough, tightly bound layer. NCERT says: 'Glycocalyx differs in composition and thickness among different bacteria. It could be a loose sheath called the slime layer in some, while in others it may be thick and tough, called the capsule.' Both make the cell sticky and protect it.
Peptidoglycan (also called murein). It is a network of sugar chains cross-linked by short peptides. The cell wall gives the bacterium its shape and gives structural support so the cell does not burst. Remember: ALL prokaryotes have a cell wall EXCEPT Mycoplasma, which is wall-less. NEET has repeatedly tested that bacterial cell wall = peptidoglycan (2016).
No. They are two separate layers. Glycocalyx is the OUTER sticky sugar coat (slime layer or capsule). The cell wall sits just below it and is made of peptidoglycan for shape and support. Students confuse them because both are outside the plasma membrane, but the glycocalyx is on top of the cell wall, not part of it.
The plasma membrane is the INNERMOST layer, so it comes AFTER (inside) the cell wall. Order from outside: glycocalyx first, then cell wall, then plasma membrane wrapping the cytoplasm. The bacterial plasma membrane is selectively permeable and can fold inward to form a mesosome. Its structure (lipid bilayer with proteins) is similar to the eukaryotic membrane.
The plasma membrane is selectively permeable, meaning it controls which molecules enter and leave the cell. In bacteria it folds inward to form a special structure called the MESOSOME. Mesosomes help in cell wall formation, DNA replication and separation into daughter cells, and also help in respiration and secretion. NEET 2023 and 2025 both tested mesosome functions.
Which of the following components provides sticky character to the bacterial cell?
Select the wrong statement
Select the correct statements regarding cell membrane in eukaryotic cell. A. Membrane of human RBCs has approximately 52% protein. B. Major phospholipids are arranged in a bilayer. C. Extensions of the plasma membrane into the cell form mesosomes. D. Tails towards the inner part of lipids are hydrophobic and thus protected from aqueous medium. E. Glycocalyx is present on the outer surface of the plasma membrane.
Try the real previous-year questions from this chapter — each with the answer and a full solution.
No. The glycocalyx is present in many bacteria but not all. When present, it may be a thin slime layer or a thick capsule. The cell wall and plasma membrane are more constant parts of the envelope (except Mycoplasma, which has no wall).
Mycoplasma. It is the only prokaryote without a cell wall, and it is also the smallest living cell (about 0.3 micrometre). This is a very common NEET fact: 'all prokaryotes have a cell wall except Mycoplasma.'
No. The cell envelope is the whole three-layered coat (glycocalyx + cell wall + plasma membrane). The plasma membrane is just the innermost single layer of that envelope.
Because it is made of peptidoglycan, gives shape and support, prevents bursting, and its structure decides whether a bacterium is Gram-positive or Gram-negative. NEET tests both the peptidoglycan fact and the Gram staining difference.
The plasma membrane is selectively permeable and controls transport in and out. It folds inward to make the mesosome, which helps in cell wall formation, DNA replication and distribution to daughter cells, plus respiration and secretion.
