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> A tour in a prokaryotic cell Issue: 2011-3 Section: 14-16



Your body is one of the most complex structures in the universe. It is made up of some 100 trillion tiny cells. In fact, there are more than 200 different types of cells in your body. Despite their amazing diversity in shape and function, your cells form an intricate, integrated network. No human invention can compete with the technical brilliance evident in even the most basic of cells.

All living cells fall into two major categories:

  • those with a nucleus
  • and those without one.

Human, animal, and plant cells have a nucleus. Bacterial cells do not. Cells with a nucleus are called eukaryotic. Those without a nucleus are known as prokaryotic.

To understand better the function of prokaryotic cells, we will take a tour in such a cell.


The tour begins!

To tour a prokaryotic cell, you would have to shrink to a size that is hundreds of times smaller than the period at the end of this sentence. Your access to the cell is prohibited by a tough, flexible membrane that acts like a brick and mortar wall surrounding a factory. It would take some 10,000 layers of this membrane to equal the thickness of a sheet of paper. But the membrane of a cell is much more sophisticated than the brick wall. In what ways?

Like the wall surrounding a factory, the membrane of a cell shields the contents from a potentially hostile environment. However, the membrane is not solid; it allows the cell to “breathe,” permitting small molecules, such as oxygen, to pass in or out. But the membrane blocks more complex, potentially damaging molecules from entering without the cell’s permission. The membrane also prevents useful molecules from leaving the cell. That’s possible, because, the cell membrane has special protein molecules embedded in it that act like the doors and the security guards.


Inside the factory

Imagine that you have been allowed past the “security guard” and are now inside the cell. The interior of a prokaryotic cell is filled with a watery fluid that is rich in nutrients, salts, and other substances. The cell uses these raw ingredients to manufacture the products it needs. . Like an efficiently run factory, the cell organizes thousands of chemical reactions so that they take place in a specific order and according to a set timetable.

Just as the operations of a factory might be governed by a central computer program, many of the functions of a cell are governed by a “computer program,” or code, known as DNA. From the DNA, the ribosome receives a copy of detailed instructions that tell it which protein to build and how to build it.

What happens as the protein is produced is nothing short of amazing!! Each one folds into a unique three-dimensional shape. It is this shape that determines the specialized job that the protein will do4. The amazing thing is that, if a protein is not precisely constructed and folded to exactly the right shape, it will not be able to do its work properly and may even damage the cell.

How does the protein find its way from where it was made to where it is needed? Each protein the cell makes has a built-in “address tag” that ensures that the protein will be delivered to where it is needed.

Although thousands of proteins are built and delivered each minute, each one arrives at the correct destination.

Bacteria consist of approximately 40 proteins, which can be likened to the parts of an engine. The amazing thing is that it can be self-made in just 20 minutes! The flagellum is attached to the cell wall of the bacterium and rotate giving the organism the ability to proceed, stop, move backwards and change direction.

Many famous inventors studied the function of the bacteria. Indicatively, an important milestone in the history of cell was in 1683 when they were first-discovered by the Danish Antony van Leeuwenhoek. In 1773, by a group of scientists, they invented Speiryllia and Bacillus. In 1872 the German botanist lays the foundations of Bacteriology.

Another example is Robert Koch, who in his studies

and work has provided invaluable assistance in medical practice and became the founder of bacteriology. In 1905, he was honoured for his contribution with the Nobel Prize in medicine. One more ex-ample is Francois Jacob, a French inventor, who with Jacques Monod, concluded that the control of enzyme levels in cell volume is the result which provides feedback to the transcription of the DNA sequences. They shared the Nobel Prize in 1965. After the examination and history in the operation of “simple’’ cells we saw how great a human life is!!



  • Princeton Weekly Bulletin.”Nuts, Bolts Of Who We Are” By Steven Schultz, May 1, 2000
  • “The Nobel Prize in Physiology or Medicine 2002” Press Release, October 7, 2002.
  • “The Origin of Life-Five Questions Worth Asking.” By Watch Tower Bible and Tract Society of Pennsylvania, 2010.
  • Encyclopedia Britannica, CD 2003 “Cell”, “The Mitochondrion and the Chloroplast”, subhead, “The Endosymbiont Hypothesis”
  • Molecular Biology of the Cell, Second Edition, by Bruce Alberts et al, 1989, p 405
  • Molecular Human Reproduction, “The role of Proteomics in Defining the Human Embryonic Secretome” By M. G. Katz-Jaffe, S. Mc Reynolds , D.K Gardner, and W. B Schoolcraft, 2009, p 271.