3 Cell Theory, Here’s the Complete Explanation

Cell theory Is Sinaumed’s looking for references on cell theory? Exactly, if Sinaumed’s is studying the study of biology, he must be familiar with cell theory, be it in plants, animals, including humans. Even though we know that cells are small things, their presence is important for us to recognize and know. 

The following is an explanation of cell theory, starting from a basic introduction, history, theory and benefits: 

Know What is a Cell?

The cell is the smallest structural and functional unit in living things. Then, why is the cell said to be the smallest structural unit? This is because it forms a collection of cells that will become a network and then form more complex organs and organ systems, namely forming larger organisms. 

Besides that, why is the cell called the smallest functional unit? This is because in the cell there are parts which each of these parts still has a specific function. That is why humans have a body structure that can be used to carry out various activities, such as thinking, eating, drinking, breathing, and so on. 

This can happen because of cooperation between organ systems, tissues, organs, which starts with cells properly. If there is any damage to the cells or they do not work together properly, it will have an impact on the larger organisms and structures in our body. 

That is why humans must realize that everything that is normal to them is not simple, but is composed of even the smallest things. To get to know more about cell theory, the following are things that Sinaumed’s needs to pay attention to when starting to learn about cell theory:    

1. Cell shape

The cells are very small and cannot be seen with the naked eye. Sinaumed’s certainly needs a magnifying device that supports it so he can see cells, such as a microscope. The tool is able to see things that are small in shape, like looking at bacteria, viruses or fungi to observe their shape and development. 

The first cell discoverer was Anthony Van Leeuwenhoek in 1623 to 1723 who he discovered using this microscope. For this discovery, many experts finally participated in observing the world of biology on matters related to cells, which cannot be held and seen directly. 

2. Cell Layout

Cells are located in every living thing, including animals, plants, and of course humans, who must have a more complex cell shape. Cells in plants, maybe we can’t see plants move significantly by themselves, but plants also have cell structures too. 

Cell structure and cell location must also differ between plants, animals and humans. However, with this collection of cells there will be cooperation between organs, organ systems, tissues so that they can help living things survive and carry out life activity processes, such as digestion, breathing, growth, and so on.

So it can be said that even though they are small, cells have an important role in the structure of living organisms. Although it is the smallest structural unit, the cell has a large functional role in living things.  

3. Constructed

Sinaumed’s needs to know that all cells are bounded by a membrane or also known as the plasma membrane. While the area inside the cell is called the cytoplasm. Each cell then at a certain stage will contain DNA as material that can be inherited for the cell’s work activities.

In addition, each cell also has ribosomes which function to make proteins that will be used as catalysts for various chemical reactions in the cell. Each of these organisms is composed of one or two different types of cells, namely prokaryotic cells or eukaryotic cells. 

The two types of cells are distinguished by the location of the DNA in the cell itself. Thus each piece of DNA in the eukaryotic enveloped organelle or nucleus is given a name within the cell contents. Meanwhile, prokaryotes do not have a nucleus. Only bacterial and archaean forms have prokaryotic cells, whereas fungi, plants, protists, and animals have eukaryotic cells.

a. Prokaryote Cell

Prokaryotic cells are unicellular organisms with a cell size that has a small size between 0.7 to 0.2. Usually these cells are composed of a cell envelope, cell membrane, cytoplasm, nucleoid, and several other arrangements. Most of these cells have a cell envelope outside the cell membrane. In addition, they usually have one coiled building block DNA molecule that concentrates nucleotides. 

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b. Eukaryote Cell

Unlike Prokaryotic cells, Eukaryotic cells have a nucleus. Thus, the cytoplasm of eukaryotes is the shape of the region between the nucleus and the cell membrane. This cytoplasm then consists again of several semiliquid medium which is also called the cytosol. 

Within the cytosol are organelles with specialized forms and functions. In some prokaryotes also do not have the cytosol. In general, these organelles are bounded by a single layer of membrane. However, it is still limited by two membranes, for example, there is an arrangement of the nucleus.



Previously, a little was explained about the discovery of cells for the first time using a microscope by Antony Van Leeuwenhoek around 1635-723. From there, scientists emerged who continued to develop and examine things that were small or microscopic, including cells in living things. 

The following is the history of cell theory from its initial discovery to its development to date: 

1. Early Discovery

The history of cell theory is also inseparable from the history of the existence of the latest magnifying device, namely the microscope. This microscope tool was first invented with two (compound) lenses at the end of the 16th century. After that, it was developed in the Netherlands, Italy and England. Until the mid-17th century, microscopes began to have the ability to magnify up to 30 times. 

British scientist Robert Hooke then designed a compound microscope that had its own light source making it easier to use. Robert Hooke began observing thin, cork-like slices through the microscope and trying to teach them. The explanation obtained from microscopic capture of cork is that it is porous like a honeycomb, but the pores are irregular.

Hooke called the pores cells because they were almost like cells or small chambers in monasteries or prisons. What Hooke actually saw were the empty cell walls surrounding the dead cells in the cork. The cell is sourced from the bark of an  oak tree as a raw material for making cork. Hooke then also observed green plants that also have cells in the form of fluids. 

Meanwhile, at the same time in the Netherlands, a scientist named Antoni van Leeuwenhoek who was also a cloth trader, created his own single-lens microscope and used it to observe various things. Leeuwenhoek then succeeded in seeing red blood cells, spermatozoids, single-celled yeasts, protozoa, and even bacteria.

Then in 1673 Leeuwenhoek began sending letters about his activities to the Royal Society, which is a scientific association in England and published them. In one of his letters, Leeuwenhoek describes things that move in saliva which he examines under a microscope. Leeuwenhoek also called it the term director general or director general in Dutch which means small animal. 

Then translated into animalcule in English by the Royal Society which is then believed to be a bacterium by modern scientists today. In 1675–1679, an Italian scientist named Marcello Malpighi then described the constituent units of a plant which he named utricle or means small bag. According to him, each of these cavities has fluid and is surrounded by walls that look solid. 

Nehemiah Grew, a scientist from England then also taught about plant cells in his writings which were published in 1682. Grew succeeded in observing many things that the little green plants built inside the cells of plant leaves which were later named chloroplasts. 

2. Development of Cell Biology

Between 1875 and 1895, there were various discoveries about the basic cellular phenomena, namely mitosis, meiosis, and fertilization, and various studies of other important organelles, such as mitochondria, chloroplasts, and the Golgi apparatus. From there was born the aspect which then focuses on studying cells which is called cytology.

The development of this new tarsus technique occurred, especially in the areas of cell fractionation and electron microscopy. This then allows the study of cytology and biochemistry to give birth to a new aspect which is also known as cell biology. Then in 1960, the scientific association of the American Society for Cell Biology was founded in New York, United States. 

Not long after, a scientific journal called the Journal of Biochemical and Biophysical Cytology appeared, changing its name to the Journal of Cell Biology. After the 1960s, cell biology has now become an established scientific discipline or study, with its own scientific associations and publications. In addition, this scientific study also has a mission to reveal the mechanism of function in cell organelles.


Cell Theory According to Experts

In its development, as Sinaumed’s has seen from its history above, cell theory continues to develop from many scientists who are trying to find out about the study of cell theory. Here is a summary to understand cell theory more easily: 

1. Schleiden Cell Theory

Schleiden argued that the cell theory is that every form of living things, including plants, is composed of cells. Schleiden’s assumption was supported by Theodor Schwann who also revealed that every living thing is composed of cells. 

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With this basis and support, Schleiden and Schwann finally formulated the cell theory. In the opinion of Schleiden and Schwann cell is a unit or the smallest unit of life or living things themselves.

2. Max Schulze’s Cell Theory

Max Schultze then revealed that the cell is the smallest functional unit form of living things. As previously explained, in cells there will be a good form of cooperation between tissues and cell organelles, so that this process can help living things to have better activities.

3. Rudolf Virchove’s Cell Theory

Rudolf Virchow also revealed the cell theory that the cell is the smallest growth unit of living things. This means that every living thing in it has cells which will then grow and develop from small to become larger organisms to function. This theory is also known as “Omne cellula e cellula” which means that each cell comes from the previous cell and will continue to grow.

Cell Function

After learning about the many cell theories above, an explanation that is no less important for Sinaumed’s to know is the function of the cell itself in living things, as follows:

1. Metabolism

Everything that occurs in chemical reactions creates living things in carrying out activities is a form of metabolism. Each of these chemical reactions then takes place inside the cell. Metabolism that occurs in cells can be in the form of catabolic reactions which are the overhaul of chemical compounds to produce energy and then made into materials for the formation of other compounds.

Besides that, it can also take the form of an anabolic reaction which is a reaction to the preparation of cell components. One of the catabolic processes that change food molecules to produce into energy in cells is cellular respiration. The process then continues in the eukaryotic mitochondria or is called the prokaryote cytosol and produces ATP. While an example of an anabolic process is a form of protein synthesis which then continues to become ribosomes and requires ATP.

2. Cell Communication

The cell’s ability to communicate is the process of receiving and sending ‘signals’ to and from other cell types. This indicates the existence of interactions between unicellular organisms to regulate the function and development of the bodies of these multicellular organisms. 

For example, bacteria communicate with each other in the process of quorum sensing or quorum sensing. This aims to determine whether their number is sufficient before finally forming a biofilm. While the cells in animal embryos will communicate to coordinate the process of differentiation into various other types of cells.

3. Cell Cycle

Sinaumed’s needs to know that each cell originates from the division of previous cells. While the process of cell life to undergo cell division to the next cell division is called the cell cycle. Usually this cell cycle consists of four coordinated processes or phases, namely cell growth, DNA replication, separation of DNA that has split into two which will then become daughter cells, and the next cell division occurs. 

4. Cell Differentiation

This cell differentiation forms the various cell types that later arise during the development of a multicellular organism occurring from a fertilized egg. For example, in mammals, which originates from a cell that develops into an organism with hundreds of different types of cells, namely muscles, nerves, and skin. The cells in the surviving embryo then carry out cell signaling to influence the gene expression of other cells and cause the differentiation process.

5. Programmed Cell Death

Cells in multicellular organisms can experience death because controlling cell populations by balancing cell multiplication does not occur properly. For example, to prevent the appearance of tumors, namely to kill cells to eliminate areas of the body that are not needed. 

Another example is during the formation of an embryo, namely the fingers on a human hand or toe will stick together, now this happens because there is hardness in the death of the cells between the fingers. So, when and where cell death occurs, it’s the same as cell growth and division, which is a very controlled process. 

Well, that’s an explanation of cell theory in the study of biology. Has sinaumedia been able to understand it? Even though it looks easy, the study of cell science is also quite complicated and a lot. So if Sinaumed’s still needs references to learn about cell theory, you can visit the sinaumedia collection at www.sinaumedia.com , such as the following book recommendations: Enjoy learning #Friends Without Limits.