Cell Structure and Organelles

If the cell is the unit of life, then organelles are the working parts that keep the cell alive. This lesson surveys the internal architecture of prokaryotic and eukaryotic cells, comparing their features and describing the roles of the major organelles revealed by electron microscopy.

Prokaryotic cell structure

Prokaryotic cells are typically 1 to 5 micrometers across and have a comparatively simple organization. Their key features include a cell wall made of peptidoglycan that provides shape and protection, a plasma membrane controlling exchange, and cytoplasm containing enzymes and ribosomes. The genetic material is a single circular chromosome located in the nucleoid, not bounded by a membrane. Many prokaryotes also carry small rings of extra DNA called plasmids, which often carry gene