Cell Biology

Cell biology or cytology is a branch of biology that deals with studies related to the structure and function of a cell-based on the concept that the cell is the fundamental unit of life.

  • A detailed study of the cellular structure and function provides a basis for studies related to tissues, organs, and the body.
  • The number of cells in an organism might differ as some organisms have a single cell while others are made up of billions of cells.
  • In the case of single-celled organisms, the singular cell is studied, whereas, for multicellular organisms, individual cells of different tissues are studied.
  • Initially, only the outer structure of a cell was studied due to the lack of complex microscopic processes.
  • Over the years, however, advancements in other areas have made it possible to study the internal cellular components of a cell.
  • Apart from the cell structure and function, cell biology also deals with cell communication and signaling.
  • Cell biology also involves the studying of the cell cycle and cell division, which provides insight into the cellular composition of an organism.
  • Cell biology is also linked with other studies like genetics, molecular biology, cytochemistry, and biochemistry.
  • Cells are distinguished as prokaryotic and eukaryotic cells based on the complexity of the cell.
  • Cell biology enables studying the biochemical mechanisms involved in cell metabolism and different forms of cellular energy.
  • Focusing on the structural and functional aspects of a single cell allows a detailed understanding of the body overall.
  • It is also easier to perform research on a single cell as it can be modified and observed efficiently.
  • Techniques in cell biology have advanced over the years with new and improved imaging techniques to observe smaller cellular organelles.
  • Cell biology, together with systemic biology, helps in the answering of complex questions like the relationship between cellular networks, the evolutionary relationship between genomes, and the complexity of the biomolecular composition of different living organisms.

Cell biology history 

The discovery of the microscope influenced the discovery of cells. The microscopist and physicist from England Robert Hook (1635-1702) took the first description of cells in 1665. His scientific experiment conducted by making thin slices of cork and matched the boxy partitions he totally observed to the cells in a monastery. Hook observed open empty spaces but he and other scientists made their suggestions by saying that these spaces can be used to transport fluid in a living plant. They did not confirm that it is a basic unit of living organisms that they were observing.

Marcello Malpighi (1628–1694), and Hooke’s colleague, Nehemiah Grew (1641–1712), continued making strong researches on plant cells, and put out the cellular structure in a plant body.

Grew matched cellular empty spaces to the gas bubbles in rising bread and made his suggestions saying that they have the same process in their formation. Animals’ cells were discovered later because it was essential for thin sections to facilitate viewing under the microscope but were difficulty to prepare. Nowadays, scientists interested in biology were totally convinced that living things are made of fundamental units. It created curious to know what those units are.

Microscope took its improvement to make their observation clearly and assisted to know more on cells and microscope chosen to be an important instrument to study life on the planet. The Dutch microscopist Antony van Leeuwenhoek (1632–1723) published his researches and observations in 1676 about single-cell organisms, or “little animalcules” the name given by him to these single celled animals. He has been respected first scientist observed red blood cells and even sperm cells in a microscope. Leeuwenhoek discovered and said many on his microorganisms, however, hundred years passed without guessing connection between cellular livings and cells that build plants and animals.

Researches continued developing and reach in 1824 where Frenchman Henri Milne-Edwards put out his suggestions on animal tissues, according him animal tissues are structured like an array of globules (the basic structure of all animal tissues was an array of “globules).

Henri Dutrochet (1776–1847) identified the relationship between plant and animal cells explicit, and mentioned his proposition saying that a cell was both just a structural and physiological unit, and clearly defined that everything comes from cells. Dutrochet in his proposal, he proposed that new cells come from old cells, and François Raspail (1794–1878) echoed this idea proposed by Dutrochet and said to be his contemporary, Raspail known as the first person who supported in mentioning one of the two main tenets of cell theory: Omnis cellula e cellula, which means “Every cell is derived from another cell.”

However, despite this ringing and famous phrase, the proposed mechanism on generation of cells has not been true. He contributed on chemical composition of cells and become the father and founder of cell biochemistry. In 1832 Barthelemy Dumortier (1797–1878) French scientist entered his description on described on binary fission in plants and was the idea to cell division in common sense.

He took his careful observation to the formation of a mid-line partition structure of both original and new cell, and Dumortier noted and took in considerations, it was as if he was going to provide clear understanding on the development of cells, “seems to us to provide a perfectly clear explanation of the origin and development of cells, which was still in obscurity explanations. His observation directed to rejection of the idea said that new cell comes from within old ones. Hugo von Mohl (1805–1872), is the one who discovered cell division despite Dumortier who preceded him. Von Mohl mentioned the word protoplasm as a material contained in the cell. Cell nucleus is also an important part of the cell and was discussed firstly by a Czech, Franz Bauer, in 1802 and was named in 1831 by Robert Brown (1773–1858) from Scotland, and also entered other parts of nucleus description. Schleiden and Schwann, took researches on cell theory and outlined their marks and contribution in 1838 and 1839. In 1838 Matthais Schleiden (1804–1881) clarified his proposition saying that each plant types or elements is made of cells. In 1839 a fellow German, Theodor Schwann (1810–1882), came up with propositions on animals’ structure.

His proposition was that all structural elements in animals are cell set products, which means that, are made by cells. Contribution of Schwann seems as imitating what cell theory on plant has suggested. He declared that the laws governing cells were the same or identical in both animals and plants. The Czech Jan Purkyňe (1787–1869), or Purkinje, has also contributed on cell theory and was single cytologist in his day and known as one of the most important formulators of cell theory. He used Schwann theory to explain his contribution. His proposition was that animals were made of cells and cell products and this is applied to plants. Other scientists also contributed to cell theory but these are main ones.

Cell definition and overview

The cell is the smallest basic unit of all living organisms. They independently do their activities, they replicate to and divide. They are also known to be building blocks of life. The science dealing with cell study is known as cell biology or cytology.

A human being is known to have more than 10 trillion of cells mathematically it is 1013cells and seen by means a microscope, means that you cannot see them by a naked eye. All living organisms are composed of cells. Cells have various forms and shapes, utilities and visibility. Cells have abilities of metabolic process and this give them ability of living independently and play a huge role in living things. Scientists and various researchers strove to understand how cell itself plays interesting functions in all livings things and how its absence leads to inexistence of living organisms.

We better know that there are animal cells and plant cells, and these cells has high percentage of similarities, however, some few differences has already mentioned within their structures. Cells are made of identical types of molecular building block and share some common characteristics. Even if cells have various common features, we take in consideration different and various cell types and this classification and categorization of cells is known as cellular diversity.

This diversity of cells differs in kinds of organisms and within metazoan or multicellular livings themselves. Commonly known characteristics shared by cells are like using the same carbon in macromolecules which is the main component within cells. It includes carbohydrates, proteins, lipids and two nucleic acids found within nucleus of living cells. All cells have DNA in which genetic characters are located and known as a genetic material of living organisms. All living organisms use their genetic material (DNA) to make proteins where it decodes before making proteins and these proteins help in energy of a cell helping also in metabolic activities of cells. Cells have ability to grow and divide despite some of cells found in multicellular organisms that lost their ability to divide and example can be given like on neurons that cannot divide.

Both animal and human cells possess different parts or organelles, and each connects with cell components by means of intracellular membrane. DNA separates from cytoplasm by nuclear membrane shaping an important large organelle called nucleus. Organelle like mitochondria which is important organelles that play a huge role in cell activities like generating Adenosine triphosphate (ATP) which a useful component in providing essential energy that facilitate various biochemical reactions that lead to formation molecules from smaller units and an example that can be taken is formation of protein through amino acids.

In multicellular organisms, cells are pointed to do and perform specific different functions. Those functions are like secretion and movements. Various molecules contribute in these functions talked above. Muscular cells of animals and humans themselves assured for synthesis of proteins that facilitate their contraction, but in non contractile cells these proteins are not synthesized. An example here is skin cells. Cells are different biochemically in multicellular livings, and also notification of shape difference is important as cells have different forms. Our look can be addressed to red blood cells that are small and disc in shape while neuron or nerve cells are long in shape, and all these forms and shapes are known as cell morphology In organisms with many cells ( multicellular) cells tend to be classified in different groups or tissues basing on their responsibilities and functions. You better know that cells and tissues organize to make organs and organs to organ systems that participate in performing different functions.

Example is digestive and cardiovascular system. Living cells always work their activity; they always need energy and this allows them to make nutrients that will continue to facilitate cell activities in synthesis of new molecules. Remember that they make molecules and transport them in different parts of the cell and all need energy with this they also expulse waste . if the process is done in appropriate manner, cells get growing and enter division. Cell activities can allow a cell to take new shapes in terms of responding to environment and also in interacting with other cells in the process called cellular communication or cell signaling.


Cell Diversity Cells are found in different organisms, and each organisms has its special cells depending on its specie. However, cells are very diverse in size, shape and their internal structure and this applied to cells found in the same organisms. This diversity of cells is influenced by their roles and function within organism’s body.

Cell Shape

Cells have different shapes due to appropriate function. Comparison can be found below where you find cells with long extensions like nerve cells that facilitate in sending and receiving impulses. You can find other cells which are flat or platlike, most of these cells are body cells and their function is protecting and covering body surface.

Thus cells develop in size according recommended function within the body of a living. Cells have different shapes. Nerve cells have long extensions. Skin cells have a shape which is flat and platelike. Egg cells have shape which is like sphere, and some bacteria are rod in shape. Some plant cells are rectangular.

Animal Cell

Components of a typical animal cell:

  1. Nucleolus
  2. Nucleus
  3. Ribosome (dots as part of 5)
  4. Vesicle
  5. Rough endoplasmic reticulum
  6. Golgi apparatus (or, Golgi body)
  7. Cytoskeleton
  8. Smooth endoplasmic reticulum
  9. Mitochondrion
  10. Vacuole
  11. Cytosol (fluid that contains organelles; with which, comprises cytoplasm)
  12. Lysosome
  13. Centrosome
  14. Cell membrane