Cell Structure

human cheek cells

The many and complex chemical reactions that are necessary to maintain life can take place only in a delicately balanced environment. 

Living cells, such as the human cheek cells shown on the top border of this page, are the life support chambers that maintain this special environment.  Cheek cells are frequently the cells that are collected for use in DNA testing for genealogy. At the right (or below if you are viewing on a cell phone screen), Mr. James Dorsey collects cheek cells as part of the launch of the Dorsey DNA Project, November 2001.

The human body contains approximately 37.2 trillion cells, most of which are less than a tenth of a millimeter across.

There are two types of cells in nature. Prokaryotic cells are the simplest cells. Each cell is an individual organism. A prokaryotic cell is basically a membrane sack filled with cytoplasm—a thick jelly like substance where all the chemical reactions required for the life of the organism take place.

Eukaryotic cells are more advanced on the evolutionary scale and are more complex in both structure and function. Eukaryotic cells can be either single cellular or multicellular.

Jim Dorsey Collecting Cheek Cells

Figure 1 Jim Dorsey collecting cheek cells for the launch of the Dorsey DNA Project, November 2001

Cell Theory

All living organisms are composed of one or more cells.

The cell is the basic unit of structure and organization in organisms.

All cells arise from pre-existing cells.

Most eukaryotic cells have three main parts

1. The cell membrane is a thin but tough covering made of lipids and proteins that forms the outside of the cell.  The cell membrane protects the inner contents of the cell, gives the cell shape and supports and controls what goes in and out of the cell.

2. The cytoplasm (means cell substance) contains water, various salts, and many large macromolecules.  The cytoplasm also contains a variety of smaller subunits or compartments of the cell called organelles which perform various tasks.

3. The cell nucleus houses the cell’s genetic material (DNA and RNA) and proteins.  The genetic material contains directions for making the cell’s proteins.

Eukaryotic cells are highly organized. They contain a variety of small subcellular structures called organelles. Organelles perform specialized tasks that are crucial to the cell's survival. Some organelles such as ribosomes and mitochondria are found in all eukaryotic cells. Other organelles perform specialized functions in specialized cells. For example, plant cells contain chloroplasts. Chloroplasts are the site of photosynthesis, the process whereby plant cell capture energy from light and store it in the form on chemical energy.

Prokaryotic Vs. Eukaryotic Cells

RichchetScience (18 Jan 2015 Prokaryotic Vs. Eukaryotic Cells [Video file] retrieved from https://youtu.be/RQ-SMCmWB1s

RichchetScience (18 Jan 2015 Prokaryotic Vs. Eukaryotic Cells [Video file] retrieved from https://youtu.be/RQ-SMCmWB1s

Be sure to check out the videos in the tabs at the top of the page for more information and entertainment about living cells.

Where Can I Go From Here?

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©️2002 - 2017 Context.info

Where Can I Go From Here?

©️2002 - 2017 Context.info

Contexo.info is a not for profit, educational website.