Note: When describing the parts of a cell, I will be describing the animal/human cell unless I specifically state otherwise.

Edit 11/4/2015: Error: When describing protein synthesis, I should’ve wrote the formation of proteins, not the copying of them. Sorry about that. – Slayden

The Cell Part I: Introduction and the Nucleus

Diagram of an animal cell. See license at the bottom for usage.
Diagram of an animal cell. Click to see a larger image. See license at the bottom for usage.

The cell is the smallest unit of life, and every life form, whether a bacterium, a fish, or a mushroom growing in the backyard, has one or more cells. All cells share two basic similarities, they contain DNA, and they have a plasma membrane. Besides that however, and a few other minor similarities, cells are very different, especially when comparing between two types of organisms. The largest difference in cells is that some have a nucleus, or an organized place to store DNA, and others do not. These two types of cells are classified as eukaryotic (meaning “true nucleus”) and prokaryotic (meaning “before nucleus”). Eukaryotic organisms include plants, animals, fungi, protists, and humans. Prokaryotic organisms include bacteria and archea. Prokaryotic organisms have a nucleoid, or a central region where DNA is stored, rather than a nucleus.

Diagram of a cell nucleus. Credit given at the bottom.
Diagram of a cell nucleus. Credit given at the bottom.

So, what exactly is a nucleus besides an organized place to store DNA? Well, the nucleus regulates all metabolic functions (anything to do with metabolism) in the cell. This is why the nucleus is often called the control center of a cell. However, calling the organelle the “brain” of a cell is inaccurate. This is because, while a nucleus does determine the characteristics of a cell, the brain does not determine the characteristics of the body. DNA determines the body’s characteristics, and DNA is found within the nuclei of cells. The DNA inside the cell nucleus contains the instructions necessary to regulate the cell’s metabolic functions. However, the DNA can’t carry out these instructions, so, a special type of RNA, known as messenger RNA or mRNA, delivers these instructions.  The DNA mentioned is organized into strands known as chromatins. The chromatins are inside a fluid known as nucleoplasm, which is found nowhere else in the cell. The nucleoplasm also contains another organelle known as the nucleolus. The nucleolus produces another type of RNA known as ribosomal RNA. This kind of RNA eventually leads to the creation of ribosomes, which are involved with protein synthesis, or the copying of proteins. Covering the nucleoplasm is a double membrane (a membrane with two layers) known as the nuclear envelope. This nuclear envelope contains pores, which are used to allow particles into the nucleus and to not allow other particles into the nucleus, with the help of proteins.

In conclusion, this paper described the difference between prokaryotic and eukaryotic cells, the former has no nucleus, or organized place to store DNA, while the latter does. This essay also described the nucleus’ function as the control center of the cell, as well as how messenger RNA or mRNA delivers the DNA’s instructions to other parts of the cell. Additionally, the paper briefly covered the role of the nucleolus as the starting point in ribosome production and the nuclear envelope’s role of letting certain particles into the nucleus and restricting others’ access, with the help of proteins acting as carriers. The nucleus is often considered the most important part of the cell for these reasons, however, it is important to know that without all the other organelles, the nucleus wouldn’t be sending instructions to anyone, and vice versa. This is important to know since many place the nucleus at supreme importance.

Image Credits and Licenses (use these if you want to use the image)

First Image (Animal Cell Diagram)

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Click here for a summary of the license (not a substitute for the license).

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Second Image (Human Cell Nucleus)

Click here to see the original file (image is in public domain, translated into over 20 languages).