Topic overview

Start with the big picture

Prokaryotes, including Bacteria and Archaea, lack a membrane-bound nucleus; their circular DNA occupies a nucleoid, and they have 70S ribosomes and no internal membrane-bound organelles. Eukaryotic cells have a nucleus, linear chromosomes, 80S ribosomes, and organelles that support compartmentalized metabolism. Differences in cell size relate to the constraints of diffusion and surface-to-volume ratio. The topic also introduces specialized human cells such as erythrocytes, neurons, muscle cells, and adipocytes, alongside stem-cell capacities. Plant and fungal cells illustrate distinct walls and other features, while common bacterial shapes provide examples of prokaryotic diversity. Together, these comparisons establish a framework for understanding cell structure and function.