Q.Distinguish between prokaryotes and eukaryotes

Step 1. Nuclear character. A prokaryotic cell's DNA lies free in the cytoplasm as a nucleoid, with no nuclear membrane around it, so it is not a true nucleus at all. A eukaryotic cell, by contrast, has a genuine, membrane-bound nucleus enclosing its DNA.

Step 2. DNA and chromosome organisation. Prokaryotic DNA is usually circular and carries no associated histone proteins. Eukaryotic DNA is usually linear and is wound around histone proteins to form proper chromosomes.

Step 3. Size and organelles. Prokaryotic cells are small, roughly 1-5 micrometres, and contain no membrane-bound organelles at all. Eukaryotic cells are much larger, roughly 10-100 micrometres, and are packed with numerous membrane-bound organelles - mitochondria, endoplasmic reticulum, Golgi apparatus and, in plants/algae, chloroplasts.

Step 4. RNA/protein synthesis, ribosomes and movement. In prokaryotes, RNA and protein synthesis are coupled together directly in the cytoplasm, ribosomes are the smaller 50S+30S (70S) type, and movement (where present) is by a flagellum. In eukaryotes, RNA synthesis happens inside the nucleus while protein synthesis happens in the cytoplasm, ribosomes are the larger 60S+40S (80S) type, and movement can involve both flagella and cilia. …

Work through the comparison table criteria one at a time - nuclear character, DNA/histones, size, organelles, ribosome type, RNA/pr …

• Saying prokaryotes have 'no DNA organisation at all' rather than the more precise fact that their DNA is circular, histone-free, and organised as a nucleoid. …