It is generally accepted that the first living cells on Earth were some form of prokaryote. In biology, a prokaryote is generally a single-celled organism that lacks membrane-bound organelles such as a nucleus, mitochondria, and chloroplasts. Genetic material is instead organized into a ring-like structure called a nucleoid. Most prokaryotes are bacteria, and the two terms are often treated as synonyms. What are the four basic shapes of prokaryotic cells? Discuss