Section: Science

8)

Which of the following structures is not found in bacteria?

1. nuclear membrane
2. cell membrane
3. chromatin
4. ribosome
5. DNA

At one time it was thought that bacteria were essentially "bags of enzymes" with no inherent cellular architecture. The development of the electron microscope in the 1950s revealed the distinct anatomical features of bacteria and confirmed the suspicion that they lacked a nuclear membrane. Structurally, a bacterial cell has three architectural regions: appendages (attachments to the cell surface) in the form of flagella and pili (or fimbriae); a cell envelope consisting of a capsule, cell wall and plasma membrane; and a cytoplasmic region that contains the cell chromosome (DNA) and ribosomes and various sorts of inclusions. In this lecture, we will discuss the anatomical structures of procaryotic cells in relation to their adaptation, function and behavior in natural environments.