| Feature | Animal cell | Plant cell |
|---|---|---|
| Cell wall | No | Yes — made of cellulose |
| Chloroplasts | No | Yes — site of photosynthesis |
| Vacuole | Small, temporary vacuoles (if any) | One large central vacuole that can fill most of the cell |
| Centrioles | Yes, a pair in the centrosome | Absent in most plant cells |
| Lysosomes | Yes | Rare; the vacuole does much of this job |
| Shape | Often rounded or irregular | Usually fixed and box-like |
| Energy store | Glycogen | Starch |
| Shared parts | Nucleus, mitochondria, ER, Golgi, ribosomes, cell membrane | Same |
Try it: open the plant cell and the animal cell side by side and look for the cell wall, chloroplasts and the central vacuole.
| Feature | Prokaryotic cell | Eukaryotic cell |
|---|---|---|
| Nucleus | No — DNA sits in the nucleoid | Yes, with a double membrane |
| Membrane-bound organelles | None | Mitochondria, ER, Golgi, lysosomes and more |
| DNA | Usually one circular chromosome, plus plasmids | Several linear chromosomes |
| Ribosomes | 70S | 80S in the cytoplasm (70S inside mitochondria and chloroplasts) |
| Typical size | About 0.5–5 µm | About 10–100 µm |
| Cell wall | Most have one (peptidoglycan in bacteria) | Plants (cellulose) and fungi (chitin); animal cells have none |
| Examples | Bacteria, archaea | Animals, plants, fungi, protists |
Try it: in the 3D bacterial cell, find the nucleoid and a plasmid — then notice that there is no nucleus to click.
Cells are either prokaryotic or eukaryotic. Prokaryotic cells (bacteria and archaea) have no nucleus and no membrane-bound organelles. Eukaryotic cells — including animal, plant and fungal cells — keep their DNA in a nucleus and divide their work among membrane-bound organelles such as mitochondria, the ER and the Golgi apparatus.
Both are eukaryotic and share a nucleus, mitochondria, ER, Golgi apparatus, ribosomes and a cell membrane. Plant cells also have a rigid cellulose cell wall, chloroplasts for photosynthesis and one large central vacuole. Animal cells have no cell wall or chloroplasts, have centrioles in their centrosome, and contain lysosomes.
A prokaryotic cell has no nucleus: its DNA, usually one circular chromosome plus small plasmids, sits in a region called the nucleoid. It has no membrane-bound organelles and is usually much smaller (about 0.5–5 µm). A eukaryotic cell has a nucleus, membrane-bound organelles and linear chromosomes, and is typically 10–100 µm across.
The nucleus, nucleolus, mitochondria, rough and smooth endoplasmic reticulum, Golgi apparatus, ribosomes, peroxisomes, the cytoplasm and the cell membrane are found in both. Chloroplasts, the cell wall and the large central vacuole are typical of plant cells; centrioles are typical of animal cells.
They are thought to descend from bacteria that were engulfed by an ancestral cell more than a billion years ago (the endosymbiotic theory). The evidence: both have their own circular DNA, bacteria-like ribosomes and two membranes, and both divide by splitting in two, much as bacteria do.
The next chapter follows the energy inside cells, then how cells divide and pass on their genes.