While all living things are made of cells, not all cells are the same. The first major division in the living world is between two types of cells: prokaryotic and eukaryotic. The main difference is simple: eukaryotic cells have a nucleus, and prokaryotic cells do not.
The word prokaryote means 'before the nucleus.' These were the first type of cells to evolve on Earth. They are much smaller and simpler than eukaryotic cells.
The word eukaryote means 'true nucleus.' These cells are larger and much more complex than prokaryotes. They make up all multicellular organisms (like you!) as well as some single-celled ones like amoebas and yeast.
Plant and animal cells are both eukaryotic, but they have a few key differences related to their function.
| Feature | Animal Cell | Plant Cell |
|---------------|--------------------------|---------------------------------------------|
| Cell Wall | Absent | Present (a rigid layer outside the membrane) |
| Chloroplasts| Absent | Present (site of photosynthesis) |
| Vacuole | Small, temporary vacuoles | Large central vacuole (stores water) |
| Shape | Irregular/Flexible | Fixed, often rectangular shape |
The cell wall gives plants their rigid structure. Chloroplasts are the organelles where photosynthesis (using sunlight to make food) happens. The large central vacuole in plants fills with water, creating turgor pressure that helps support the plant.
Which type of cell is believed to have evolved first on Earth?
Which of the following organelles is found in both prokaryotic and eukaryotic cells? A) Nucleus B) Mitochondria C) Ribosome D) Chloroplast
A scientist discovers a new organism. Its cells are observed to have a cell wall and chloroplasts. This organism is most likely a(n) ________.