Which one of the following structures or components is not always present in living cells ?
- (a)Cell wall
- (b)Plasma membrane
- (c)Cytoplasm
- (d)Genetic material
Correct — A, Cell wall. Three features are universal to all living cells — a plasma membrane, cytoplasm and genetic material. A cell wall is not: animal cells, and some microbes such as Mycoplasma, have no cell wall at all, while plants, fungi and bacteria do. So the structure that is not always present is the cell wall.
- (b)Plasma membrane — Every living cell is bounded by a plasma membrane — it is a universal feature, so it is always present.
- (c)Cytoplasm — All cells contain cytoplasm, the internal fluid where the cell's machinery operates — always present.
- (d)Genetic material — Every cell holds genetic material (DNA), so this too is always present, whether enclosed in a nucleus or lying free.
The three things common to every cell are a plasma membrane, cytoplasm and genetic material — these define what a cell is. A cell wall is an extra outer layer found in plants (cellulose), fungi (chitin) and bacteria (peptidoglycan), but absent in animal cells and in wall-less microbes like Mycoplasma.
The question asks for the feature that is NOT universal. Membrane, cytoplasm and DNA are present in every cell; the cell wall is the odd one out because animal cells manage without it.
- Universal cell features: plasma membrane, cytoplasm and genetic material.
- A cell wall is present in plants, fungi and bacteria.
- Animal cells and Mycoplasma have no cell wall.
- The plasma membrane, not the wall, is the true boundary of every cell.
The cell wall is the non-universal structure — option (a).
- Assuming every cell has a wall — animal cells do not.
- Overlooking that DNA is present even where there is no nucleus.
Asked as a 'which structure is not always present / not universal' item.
No directly related past PYQ was found.
- practice — not a real PYQ
Which of the following is present in ALL living cells?
- (a)Cell wall
- (b)Chloroplast
- (c)Plasma membrane
- (d)Large central vacuole
Answer(c) Plasma membrane — the one boundary common to every cell.
- practice — not a real PYQ
Which type of cell characteristically lacks a cell wall?
- (a)Bacterial cell
- (b)Plant cell
- (c)Fungal cell
- (d)Animal cell
Answer(d) Animal cell — it has only a plasma membrane, no wall.