Lecture 2 - The Cell Theory

2. The Cell Theory The Development of the Cell Theory The cell theory is one of the primary concepts which has formed the basis of the contemporary biology – the entire living matter is made up cells, and cell is the basic structure. The development of the cell theory was a gradual process, marked by significant contributions from several scientists: • Robert Hooke (1665): Thus Robert Hooke was the first to describe cells after dissecting the cork under the microscope. He also named it the cell because cork appeared organically cellular, like the small monks’ cells or cellulae in monasteries. • Anton van Leeuwenhoek (1674): With the help of an even bigger lens, Leeuwenhoek was the first to note the existence of live material now called cells even bacteria and protozoa which he called animalcules. • Matthias Schleiden and Theodor Schwann (1838-1839): Schleiden a botanist fully supported by Schwann, a zoologist asserted the biological cell theory stating that all plants and animals are made up of cells. They state the basic concept that the cell is the most primitive of all living organisms and provided the foundation for the cell theory. • Rudolf Virchow (1855): Another aspect contributed to the cell theory by Virchow by declaring that “Omnis cellula e cellula”, this explains that all cells originate from other existing cells. This refuted the earlier employed concept of generation known as spontaneous and put more stress on the continuity of the life cycle. Cell theory can be described in several main principles: 1. Every known form of life is made up of one or many cells. This principle proclaims that cell is the common entity which is found in both single celled organism such as bacteria and even in the complex and large organisms such as human being. 2. Cell is the most fundamental organization level of matter existing in the living organisms. Cells are not only the structural building blocks but also functional units where metabolic, growth, and reproductive process occurs. 3. The formation of all cells is from some other existing cells. This principle is closely linked to the basic recognition of the life cycle and the belief that through reproduction and cell division such as mitosis and meiosis is paramount in the cycle of life. Consequences or the Cell Theory The cell theory has profound implications across various fields of biology: • Understanding Disease: Depending on their degree of complexity, many diseases have their origin in the cell, for example cancer that is characterized by uncontrolled and unregulated cell division. These diseases can be analyzed at the cellular level with help of the cell theory. • Developmental Biology: Development relies on the cell theory since it offers a clue on how a single fertilized egg can produce a large organism with many cells undergoing division and then acts of differentiation. • Biotechnology: Cell theory fundamentals are the basis of numerous applications of biotechnology such as, tissue engineering, regeneration medicine and genetic engineering. For example, in stem cell research, it presupposes that stem cells have the ability to divide and turn into different cells. • Evolution: The cell theory also upheld the evolutionary theory through its examination of the affinity of descent which all organisms bear. Since most of the organisms’ cells have features that are like the other, it is believed that they originated from the same source. While the cell theory remains a cornerstone of biology, it has been refined and challenged in several ways: • Viruses and Prions: Viruses violate the cell theory because they are not cells or even a group of cells that is capable of performing activities in … Viruses and prions, which are abnormal proteins, are other issues that make one question the fundamental aspects of life and its connection to cells. • Endosymbiotic Theory: The Endosymbiotic Theory that postulates that the mitochondria and chloroplasts found in eukaryotic cells are dormant prokaryotic organisms, has enlightened people on the evolvement of cells. • Multicellularity: About organization of cooperation, communication and differentiation of single cells within multicellular organism occurs the questions in the context of the multicellularity research.