Anatomy of The Cell

Sketch of cells growing on the root tip of an onion. Credit: Wilson, Edmond B.

Happy new year everyone! Previously we discussed how cells were discovered and that they are the building blocks of an organism. Today, we are going to dig deeper and find out what cells are made of and what they do.

Types of cells

You may have heard that there is more than one type of cell and it is true! The cell that makes a bacteria is completely different from the cell that makes us. Generally, cells are divided into two main groups: prokaryotes and eukaryotes. Don’t be put off by their weird names. The difference between prokaryotes and eukaryotes is quite simple: prokaryotes are in a way, ‘simpler’ than eukaryotes. Bacteria and Archaeans are prokaryotes.

Prokaryotes mainly consist of a cell membrane (which is needed to keep the cell contents inside), sometimes a cell wall or a capsule for protection, cytoplasm, which the liquid that a cell is filled with and needs in order to function, genetic material which is needed in order to reproduce, and ribosomes that help with translating the genetic material. Some prokaryotes can also have a Flagellum, which is a ‘tail’ that helps them swim around and Pili, which helps them stick to surfaces or transfer genetic material from one bacteria to another. Below is a schematic of a bacteria, showcasing the essential parts of a prokaryotic cell.

Anatomy of a typical prokaryotic cell. Image credit: Mariana Ruiz Villarreal.

Now when it comes to eukaryotes, things get a bit more complicated than that. Since the general theory is that eukaryotes stemmed from prokaryotes, they are more advanced, have more stuff in them and as a result, can perform more tasks. Most animals we know on this planet, including us, are made out of eukaryotes. Eukaryotes are amazing cells! They are basically this little factory that does all which is necessary for us to survive. Not only are they more advanced than prokaryotes in their anatomy, they also have the ability to specialize and give birth to all kinds of cells. But more on that in later posts. For now, let’s look at what a typical eukaryote consists of.

A major difference between a prokaryote and a eukaryote is the presence of a nucleus. As seen above, in prokaryotes the genetic matrial is within the cytoplasm. Free to roam around within the cell, but that is not the case in eukaryotes since the genetic material is walled in forming a nucleus.

Since eukaryotes need to do more advanced stuff in order to survive, they also have what we call ‘membrane bound organelles’. These organelles are basically, tiny little machines inside a cell which have specific tasks. Mitochondria is a famous example of an organelle!

While our cells and most animal cells don’t have a capsule or a cell wall, plant cells do. But, the cell wall in a plant cell is made out of different material than the one in a prokaryote. A plant cell also has a few organelles which are not present in an animal cell. Below is a schematic of what’s normally present in a eukaryote cell. In later posts, we will go in depth and discover what role each part plays in our biology.

Image credit: Mariana Ruiz Villarreal.

Bibliography

Alberts, B. (2008). Molecular biology of the cell. New York: Garland Science Taylor & Francis.

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