Lesson: Chapter - 4

Types of Cells

There are two major types of cells: prokaryotes and eukaryotes. Eukaryotic cells, whose name derives from the Greek eu, meaning “good,” and karyon, “kernel” or “nucleus,” have a nucleus and membrane-bound organelles. Prokaryotic cells, whose name derives from the Greek pro, meaning “before,” contain neither nucleus nor organelles. As the names imply, prokaryotic cells are less evolutionarily advanced than eukaryotic cells.

Video - Types of Cells

Prokaryotes

Prokaryotes include some of the most primitive forms of life: bacteria and blue-green algae (also known as cyanobacteria). Prokaryotic organisms are generally single-celled.

Video - Prokaryotes and Eukaryotes

Prokaryotes have a cell membrane, and they are made up of generally undifferentiated fluid, called the cytoplasm, in which floats a circular ring of DNA that controls the functioning of the cell. Prokaryotes maintain their shape through a cytoskeleton and have ribosomes that float in the cytoplasm. In addition, some prokaryotes have a special type of cell wall made of a protein-sugar combination called peptidoglycan. A few prokaryotes possess whip-like tails called flagella that help propel the cells through water.

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