The Biology of Cell Theory and Eukaryotic Cell Components

In Senior Secondary School, I loved the biology of Cell Theory. I was always repeating this because it was the basis of the course that year and needed to be passed to move to the next class. I actually passed that course with flying colors and it is in that spirit that I am going to be taking you through the Biology of Cell Theory.

When talking about cells, the year 1655 cannot be overruled. it was the year that the father of Cells, Robert Hooke took a thinly sliced cork under a crude microscope and found out it had cells that were honeycomb-like structures. The cells didn't have any nuclei in them but in 1674, Anton Van Leeuwenhoek observed the first living cell where he then noticed that they had nuclei. As the year went scientists continued to research cells and in 1850, Rudolf Virchow demonstrated that normal cells could become diseased cells in normal tissue. In 1855, he published his aphorism titled “omnis cellula e cellula” (“every cell stems from another cell")

wikimedia Common

The cell theory is made up of four main concepts which are; All Living things are made up of cells, Cell is the basic functional unit of life (well, you can argue that proteins are the basic unit of life but Cells are the basic functional unit of life), Cell arises from pre-existing cells, and Cell carry genetic information known as Deoxyribonucleic acid (DNA) that is transferred from parent to daughter cell. While this theory is important to prokaryotes, and Eukaryotes, it isn't the same with Viruses as they break the third and fourth theories as they do not need to come from pre-existing cells, and do not need DNA or transfer DNA to daughter cells. Viruses cannot reproduce on their own, they replicate within other cells that they have invaded. They are majorly made up of RNA and just a few carry DNA.

Let me quickly discuss Eukaryotes a little. They are types of cells that are made up of membrane-bound organelles and they contain a true nucleus and linear DNA compared to prokaryotes that have no nucleus, and circular DNA. Eukaryotes are known to possess organelles that are able to function independently of themselves, and their membranes are made up of phospholipid bilayers with hydrophobic heads and hydrophilic tails with cytoplasm located both outside and inside the organelles. Let me quickly discuss the organelles, and I will start with the nucleus.

The Nucleus is the control center of the cell, it is the major source of life in the cell as it contains genetic material DNA. It is surrounded by the nuclear membrane which separates the nuclear environment from the cytoplasm although it possesses nuclear pores which allow for the exchange of materials between the nucleus and the cytoplasm. The nucleus is made up of other structures such as the Nucleolus, the Nucleoplasm, the Nuclear pore, and the Nuclear envelope. The DNA contains coding regions which are known as genes. In the nucleolus, rRNA is synthesized. DNA is bound in a linear pattern coiled around histones and a cell would have 46 chromosomes which are 23 pairs which are 22 pairs of normal chromosomes and 1 pair of sex chromosomes.

The mitochondria are another organelle in the eukaryote cell. As my teacher would say then, it is the powerhouse of the cell, and I do not think it has changed. It contains the mitochondria barrier which is the outer layer and the cristae which is the inner membrane where the electron transport chain goes down. The mitochondria are semi-autonomous, replicating independently of the nucleus through Binary Fusion, and possessing their own DNA known as Mitochondrial DNA. it also contains the enzyme Cytochrome C within its Intermembranous Space. The main function of the Mitochondria is to produce ATP and when it is damaged, ATP is not produced.

Another Organelle in the eukaryotic cell is Lysosome. Garbage man of the cell, as my teacher would call it because it engulfs and removes organelles in the cell. It is prevented from damaging the cell through an enzyme known as Lysosomal Membrane. Another organelle is the Peroxisome which contains Hydrogen Peroxide. They metabolize waste along with the Lysosome. They participate in the synthesis of phospholipids.

The Endoplasmic reticulum is another membrane, and it is attached to the nuclei envelope. It is made up of the rough endoplasmic reticulum and the smooth endoplasmic reticulum. The rough contains ribosomes which allow for the transportation of proteins to be secreted. While the smooth endoplasmic reticulum is responsible for lipid synthesis, detoxification, and transportation of protein from the Rough endoplasmic reticulum to the Golgi Apparatus.

The Golgi Apparatus is the organelle in the cell where the proteins and lipid molecules are sent to get packaged by adding carbohydrates, sulfates, and phosphates so they can get through the cell membrane and maximize the effect and work of the protein.

Another component of a eukaryotic cell is the cytoskeleton. The cytoskeleton provides structure to the cell and helps to maintain the shape of the cell. It aids in transporting materials in the cell. The cytoskeleton is made up of three components which are the intermediate filaments, the microfilaments, and the microtubules. The intermediate filaments are a diverse group of filamentous proteins (keratin and Desmin). They are responsible for cell adhesion or maintenance of the integrity of the cytoskeleton, giving the cell its rigidity. They also help to anchor other organelles in the cells. The microfilaments are solid polymerized rods of actin, which provide protection to the cells. They also play roles in cytokinesis in the formation of the cleavage furrow during cell mitosis. Microtubules are hollow polymers of tubulin which help in the movement of proteins in and out of the cell body. They are also a major component that makes up flagella and cilia.

In the end, a lot of do not remember that the science of biology has to do with cells, and these cells are prokaryotes, eukaryotes, and viruses. Understanding these cells is the basis of biology, and Cells are very important in every living thing.

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References

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https://royalsocietypublishing.org/doi/10.1098/rsnr.2004.0055

https://www.livescience.com/robert-hooke-english-polymath

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2603088/

https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/cell-theory

https://bio.libretexts.org/Bookshelves/Introductory_and_General_Biology/Book%3A_General_Biology

https://www.osmosis.org/answers/eukaryotic-cell

https://www.nature.com/scitable/topicpage/eukaryotic-cells-14023963/

https://bio.libretexts.org/Bookshelves/Introductory_and_General_Biology

https://bio.libretexts.org/Bookshelves/Introductory_and_General_Biology

https://www.genome.gov/genetics-glossary/golgi-body

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4700099/

https://www.nature.com/scitable/topicpage/microtubules-and-filaments-14052932/