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Cell Theory and Cell Types

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Cell Structure

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Cell Theory and Cell Types


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You will be introduced to the Cell Theory, and you will classify cells as prokaryotic or eukaryotic through an activity using dyes.

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Now You Know

After completing this tutorial, you will be able to complete the following:

  • Describe the three tenets of Cell Theory.
  • Describe the contributions of Hooke, Leeuwenhoek, Schleiden, Schwann, and Virchow in the formation of the Cell Theory.
  • Explain that eukaryotic cells have membrane-bound organelles such as a nucleus or mitochondria.
  • Explain that prokaryotic cells do not have membrane-bound organelles such as a nucleus or mitochondria.
  • Classify cells as prokaryotic or eukaryotic based on their characteristics.

Everything You'll Have Covered

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.

Tutorial Details

Approximate Time 20 Minutes
Pre-requisite Concepts Students should be familiar with these terms: cell, cell membrane, chloroplast, cytoplasm, DNA, dye, endoplasmic reticulum, eukaryote, golgi apparatus, lysosome, microscope, nucleus, organelle, prokaryote, and ribosome.
Course Biology
Type of Tutorial Concept Development
Key Vocabulary amoeba, animal, cell, cell membrane, cell theory