A characteristic of a prokaryotic cell is its lack of a defined nucleus and organelles, which distinguishes it from eukaryotic cells. Prokaryotes, such as bacteria and archaea, have a simple structure with a single circular chromosome and often possess a cell wall. They reproduce asexually through binary fission and can thrive in various environments. Prokaryotic cells play crucial roles in nutrient cycling, environmental processes, and human health, contributing significantly to biosphere functions.