1.1.1: Eukaryotes and prokaryotes
Not started yet — this one needs some love.
Eukaryotic cells (plants, animals, fungi, protists):
genetic material enclosed in a nucleus
typical size 10–100 µm
Prokaryotic cells (bacteria):
no nucleus — genetic material is a single DNA loop (circular chromosome)
may also have plasmids (small extra rings of DNA)
have a cell wall, but it is NOT made of cellulose (unlike plant cell walls)
typical size 1–10 µm (much smaller than eukaryotic cells)
Both cell types have cytoplasm, a cell membrane and ribosomes.
Scale: 1 m = 10³ mm = 10⁶ µm = 10⁹ nm.
use standard form for very small values, e.g. 1 µm = 1 × 10⁻⁶ m
Order of magnitude: each factor of 10 is one order of magnitude — e.g. a 10 µm cell is one order of magnitude larger than a 1 µm bacterium.
Common exam mistakes
Prokaryotic DNA is a loop (circular chromosome) — students frequently say it is 'strands' or 'a strand', which is wrong.
Prokaryotes do have ribosomes — a very common misconception is that they don't.
Do not confuse the prokaryotic cell wall with the plant cellulose cell wall — they are made of different materials.
When writing values in standard form, take care with powers: 1 µm = 1 × 10⁻⁶ m (not 10⁻³).
Protists (e.g. Plasmodium) are eukaryotic, not prokaryotic — they have a nucleus. Do not describe prokaryotic features (no nucleus, circular DNA loop) when answering questions about protist cells.