Prelim Biology: Cell Organelles of Prokaryotes

5 Mins Read | By Simon Tang

Key Points Summary
  • Prokaryotic Cells do not have any membrane bound organelles, so no nucleus, mitochondria, nor chloroplasts.
  • They have a cell wall, cell membrane, nucleoid, ribosomes, and cytoplasm.
  • The most common prokaryotic cells are bacteria.
What Are They?

Cells are the basic building blocks of life. From blue whales to bacteria, all life is made up of these microscopic spheres. Just like how a human being has many organs, cells are made up of many organelles. These act very similar to real organs; they perform a very specific role to help the organism live. This blog is going to be going through the different organelles of prokaryotic cells.

What Parts Do They Have?
LadyofHats, Public domain, via Wikimedia Commons

Prokaryotic cells are cells that are primarily characterised by their lack of membrane bound organelles. This means that they do not have any organelles that have a membrane surrounding it, like a nucleus or mitochondria. In Greek, prokaryote is broken down into πρό (pro, ‘before’) and κάρυον (karyon, ‘nut’ or ‘kernel’).

The most common organisms that are made up of prokaryotic cells are bacteria.

Below is a summary of the different parts:

Cell Wall – The Exoskeleton

The cell wall is a protective outer layer that offers structural rigidity to the cell. The cell wall is permeable to small molecules, such as water, oxygen, and carbon dioxide. Think of this as like an exoskeleton, like what crabs have!

Plasma Membrane – The Skin

The cell plasma membrane surrounds the cytoplasm (below) and separates the internal cell environment from the external environment. The plasma membrane is permeable to small molecules such as water, oxygen and carbon dioxide. It has a huge variety of embedded proteins to regulate the transport of other molecules such as ions, sugars, amino acids, and lipids. It is similar to our skin, how it only lets in some molecules.

Ribosomes – The Production Line

The ribosomes in a cell are like the production line in a factory. They make all the proteins in the cell by stringing together the correct sequence of amino acids. Proteins are essential as building blocks for living systems, as well as to act as catalysts to speed up essential chemical reactions.

Nucleoid – The Brain

The nucleoid is the part of the prokaryote that contains all or most of the genetic material. In contrast to the nucleus of a eukaryotic cell, it is not surrounded by a nuclear membrane. There can also be plasmids, which are small circular DNA in bacteria. This acts as the control centre, like a brain, for the entire cell.

Cytoplasm – The Water in your Body

The cytoplasm is a thick solution that fills each cell and is enclosed by the cell membrane. It is mainly composed of water, salts, and proteins. It is responsible for regulating the concentration of salts, as well as transport of molecules throughout the cells.

What about Eukaryotic Cells?

There are two main types of cells that life is made up of – prokaryotic and eukaryotic cells. You can learn more about eukaryotic cells here.

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