Q1.
But what do their cells look like? Are they like the plant and animal cells we just learnt about, or are they different?
Answer
They are partly like plant and animal cells and partly different — and the differences are exactly what separate one kind of microbe from another.
What is the same: like animal and plant cells, the cells of microorganisms are also surrounded by a cell membrane, and they contain cytoplasm.
What is different:
| Microorganism | How its cell differs |
|---|---|
| Fungi (yeast, moulds) | Have a cell wall in addition to the cell membrane, but no chloroplasts — so they cannot make their own food through photosynthesis |
| Bacteria | Do not have a well-defined nucleus or a nuclear membrane. Instead they have a nucleoid. This feature distinguishes them from the cells of yeast, protozoa, algae, fungi, plants and animals |
| Protozoa (Amoeba, Paramecium) | Single-celled, with a well-defined nucleus; carry out every life process in one cell |
| Algae and microalgae | Contain a green pigment, so they make their own food using sunlight |
Some microbes are unicellular (bacteria, protozoa, and yeast among the fungi) and some are multicellular (moulds, some algae).
Why we need a microscope to tell them apart: all these differences lie inside a body far below the size the eye can see. A microscope that magnifies 100 to 400 times shows the shape and the main parts. To see the smaller components inside a cell you need an electron microscope, which magnifies the cell about 10,00,000 times.