ABSTRACT
The cell is the building block of all organisms. Fig. 2.1 shows a typical eukaryotic cell as well as a typical prokaryotic cell. A eukaryotic cell (top panel in Fig. 2.1) has a nucleus and is found in more evolved organisms. A prokaryotic cell (bottom panel in Fig. 2.1) does not have a nucleus and is always single-cellular, e.g., bacteria. As shown in these figures, each cell is a very complex system that includes a number of parts and structures.
