by Laura Sestak, Christ The King School
Cells are a feature shared by all organisms. A cell is the basic unit of structure and function of life.
There are many different kinds of cells. Cells that have membrane-bound structures are called
eukaryotic cells and cells that do not have membrane-bound structures are called prokaryotic cells.
All organisms except bacteria are made up of eukaryotic cells.
Many organisms, including bacteria are unicellular, or made of only one cell. This single cell carries
out all the activities that keep the organism alive and allow it to reproduce. Organisms such as
earthworms, trees, mushrooms, and humans are multicellular, or made of many cells. These cells
work together to keep the organism alive and help it reproduce. Many cells in multicellular
organisms are specialized to do only certain jobs. Each specialized cell in a multicellular organism
works with other similar cells to carry out a specific job.
Cells come in all sizes and shapes, but most are microscopic.