Biology · A Unity and diversity. The idea in plain words, the rules to remember, the mistake to avoid and a worked example, written and checked by Mega Lecture.
All living organisms are made of cells. Every cell has a plasma membrane, cytoplasm, DNA as genetic material and ribosomes.
Prokaryotes (bacteria) are small and simple: no nucleus, a loop of DNA lying in the cytoplasm, 70S ribosomes and no membrane-bound organelles. Eukaryotes have a nucleus with a double membrane, 80S ribosomes and membrane-bound organelles such as mitochondria.
Cells are too small to see without a microscope, so you must be able to change between image size and actual size. Electron microscopes have much better resolution than light microscopes, so they show small structures such as ribosomes and membranes.
Dividing millimetres by micrometres without converting. Change the image measurement to micrometres first (multiply mm by 1 000).
Answer: 3 µm
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