Cambridge O Level Biology · Syllabus 5090 · Cells
Bacterial cell
What is Bacterial cell?
A cell that has a cell membrane, cytoplasm, ribosomes and a cell wall which is not made of cellulose. Its genetic material is a circular molecule of DNA lying free in the cytoplasm, sometimes accompanied by small extra circles of DNA called plasmids. A bacterial cell has no nucleus, no mitochondria and no chloroplasts.
This definition is part of the Cells chapter in Cambridge O Level Biology.
Bacterial cell in context
Animal, plant and bacterial cells all share a cell membrane, cytoplasm and ribosomes, but they differ in what else they contain. An animal cell also has a nucleus and mitochondria. A plant cell adds a cellulose cell wall, a permanent sap vacuole and, in its photosynthetic cells only, chloroplasts. A bacterial cell has a cell wall that is not made of cellulose, circular DNA lying free in the cytoplasm and sometimes plasmids, but no nucleus, no mitochondria and no chloroplasts. In every cell the membrane controls what enters and leaves; a cell wall only supports, because it is fully permeable.
A cell is the smallest structural and functional unit considered in this syllabus. Cell structures are not labels to be memorised in isolation: each one performs work that keeps the cell, and therefore the whole organism, alive. Topic 1 asks you to identify those structures in animal, plant and bacterial cells, to state what each one does, to obtain your own evidence with a light microscope, to record that evidence as a biological drawing, to convert between image size and actual size using magnification, and to explain how specialised cells are built into tissues, organs, organ systems and organisms.
Common mistakes with Bacterial cell
- Writing two separate lists when the question said compare. Repair Put both organisms in the same sentence: “A plant cell has a nucleus, whereas a bacterial cell does not.”
Questions students ask about Bacterial cell
Do bacterial cells have DNA if they have no nucleus?
Yes. A bacterial cell has a circular molecule of DNA lying free in the cytoplasm, and sometimes small extra circles of DNA called plasmids. What it lacks is a nucleus to enclose that DNA, together with mitochondria and chloroplasts. It still has a cell membrane, cytoplasm, ribosomes and a cell wall, although that wall is not made of cellulose.