ZingPath: Cell Structure

The Cell Theory states that all living organisms are composed of one or more cells, all cells come from existing cells, and cells are the basic units of living things. This theory was developed over hundreds of years through the discoveries of many scientists and the invention of the microscope. In 1665, Robert Hooke observed that a slice of cork looked like small chambers under a microscope. He named these empty chambers, "cells." Following Hooke's discovery was the discovery of living cells also viewed with a microscope. In 1674, Anton Leeuwenhoek described these tiny moving organisms. In 1838 Matthias Schleiden noticed that all plants were made of cells. Theodor Schwann, followed this in 1839, noting that all animals were made of cells. Later in 1855, Rudolf Virchow discovered that cells came from existing cells. Together, these discoveries led to the development of the three tenets of the Cell Theory.

Cells can be placed into one of two categories, prokaryotic or eukaryotic. Prokaryotic organisms are unicellular, while eukaryotic organism can be unicellular or multicellular. Eukaryotic cells also tend to be bigger in size than prokaryotic cells. Prokaryotic cells are less complicated than eukaryotic cells and evolved before eukaryotic cells. Eukaryotic cells contain membrane-bound organelles such as a nucleus and mitochondria. Examples of prokaryotic organisms are bacteria. Examples of eukaryotic organisms are animals, plants, fungi, and protists.

To determine if a cell is eukaryotic or prokaryotic requires the evaluation of the organelles. To do this, a microscope can be used. Many cell parts are not visible under a microscope without a dye or stain. Certain dyes can be used to stain specific cell parts. For example, the dye Dapi stains the nucleus pink. The dye Mitotracker dyes mitochondria orange. Both of these dyes could be used to identify a cell as either prokaryotic or eukaryotic.