Cell wall is not present in cells of

The correct answer is D, Humans. Human cells, like all animal cells, have only a flexible plasma membrane on the outside and no rigid cell wall. The cell wall is a tough non-living layer outside the plasma membrane that gives shape and protection to the cell and stops it from bursting when water enters. Animal cells do without it because they need flexibility to move, change shape and form varied tissues such as muscle and nerve; the cytoskeleton gives them support instead. Option A is wrong because bacteria have a cell wall made of peptidoglycan, also called murein, and many antibiotics such as penicillin work by blocking its formation. Option B is wrong because plant cells have a cell wall made mainly of cellulose, which keeps them rigid and lets plants stand upright. Option C is wrong because fungi have a cell wall made of chitin, the same tough substance found in the outer covering of insects. Exam tip: wall materials: plants cellulose, fungi chitin, bacteria peptidoglycan; animal cells have none.