4.1.4 Types of Cells

​All organisms are composed of cells.
Unicellular organisms consist of a single cell
Multicellular organisms consist of many cells.

Biologists often divide living things into two categories based on the structure of their cells.

These categories are:

• prokaryotes

• eukaryotes

​A prokaryote consists of a single prokaryotic cell.

Prokaryotic Cells: lack a nucleus to surround their DNA and are unicellular, meaning they consist of one cell, they are simple in structure.

​plasma membrane: which is a flexible barrier that surrounds the cell and holds the cell contents inside

​ribosomes: are organelles that produce proteins

​cell wall: a rigid structure that supports and protects the cells

​cytoplasm: jelly-like substance found in living cells that suspend, or hold the organelles

Eukaryotic Cells

All eukaryotic cells contain a nucleus that holds the cell's genetic material.

The nucleus is a type of membrane-bound organelle. A membrane-bound organelle is a structure within a cell that is surrounded by a membrane.

Eukaryotic cells contain other membrane-bound organelles that you will learn about in upcoming lessons. Prokaryotes lack membrane-bound organelles.

Eukaryotic cells also contain many of the same organelles as prokaryotes. Like prokaryotes, all eukaryotic cells contain:

• plasma membrane

• cytoplasm

• ribosomes

Let's wrap it up...


Prokaryotes are organisms in the Bacteria and Archaea domains

Prokaryotes are unicellular, small, and lack a nucleus

Eukaryotes are large and contain a nucleus and membrane-bound organelles

Both prokaryotes and eukaryotes contain cytoplasm, ribosomes, and a plasma membrane.

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