ABSTRACT

All cells are one of two basic types. Most of the organisms with which you are most familiar, including animals, plants, and fungi, are composed of eukaryotic cells. On the other hand, many of the microorganisms we will consider in this text are composed of prokaryotic cells (Figure 3.1). When you visit the doctor because of “strep throat,” or if you suffer through a case of “traveler’s diarrhea” on an overseas trip, you are experiencing problems caused by prokaryotes. On the other hand, if you use vinegar on your salad, or enjoy a cup of yogurt for lunch, you can thank the prokaryotes that produced them. Much of the oxygen we breathe is produced by prokaryotes, and when animals and plants die, the nutrients in these organisms are returned to the environment, in large part due to prokaryotic activity. Bacterial cells are prokaryotic, as are the cells of another large group of microscopic, single-celled organisms, the archaea. Before we discuss the differences between prokaryotic and eukaryotic cells, however, let us consider some of the things they have in common.