Worked example 1
A scientist observes two different cells, Cell A and Cell B, under a microscope. Their key features are recorded in the table below.
| Feature | Cell A | Cell B |
|---|---|---|
| Nucleus | Absent | Present |
| --- | --- | --- |
| Ribosomes | Present | Present |
| Mitochondria | Absent | Present |
| Cell wall | Present (peptidoglycan) | Present (cellulose) |
| DNA arrangement | Circular chromosome in nucleoid | Linear chromosomes in nucleus |
- Identify whether Cell A is a prokaryotic cell or a eukaryotic cell. Justify your answer using two features from the table.
- Identify whether Cell B is a prokaryotic cell or a eukaryotic cell. Justify your answer using two features from the table.
Show solution outline
- Cell A is a prokaryotic cell.
- Justification 1: It lacks a true nucleus. Prokaryotic cells do not have their genetic material enclosed within a nuclear membrane.
- Justification 2: It has a cell wall made of peptidoglycan. This is characteristic of bacterial (prokaryotic) cell walls, distinct from eukaryotic plant or fungal cell walls. (Other valid justifications include: absence of mitochondria, circular DNA in nucleoid).
- Cell B is a eukaryotic cell. (Specifically, a plant cell due to the cellulose cell wall).
- Justification 1: It possesses a true nucleus. Eukaryotic cells have their genetic material (DNA) enclosed within a double membrane, forming a nucleus.
- Justification 2: It has mitochondria. These are membrane-bound organelles found in eukaryotic cells for aerobic respiration. (Other valid justifications include: cell wall made of cellulose, linear chromosomes in nucleus).