 Hi everyone I'm CNU and I'm Angela Stoddak and we both work at the Research School of Biology here at ANU. We work at the leaf cell level to make useful changes to the whole plant and today we will be exploring the differences between prokaryotic and eukaryotic cells. All living things are made up of cells. This includes single celled organisms like bacteria as well as multicellular organisms like you. The simple cells which evolved first are called prokaryotic cells. All prokaryotes are single celled and have key characteristics. First they have a plasma membrane. This is filled with a substance called the cytoplasm. In the cell you will also find DNA which codes for all the proteins that the cell can produce. The machines that build those proteins are called ribosomes. In this ancient world full of single celled life something amazing happened. One cell engulfed another but didn't digest it. This rare but important event is called endosymbiosis. Endo meaning within and symbiosis referring to the new partnership formed. The cells that were engulfed took on new and specialized functions which added to the complexity of the new cell. These more complex cells are called eukaryotic cells. They contain several membrane bound organelles which perform specialized functions. Some but not all of these organelles arose through endosymbiosis. For example the mitochondria has two membranes which indicates that it was formed through an endosymbiotic event. Another important difference is that the DNA is now linear and packaged into chromosomes inside the nucleus. In fact the term eukaryote describes this. U meaning true and karyon meaning nucleus. In contrast the pro in prokaryote describes that they arose before the nucleus. These simple prokaryotic cells are the evolutionary ancestor of eukaryotic cells which allowed for the evolution of complex multicellular life.