Fundamentals of Cell Theory
We always hear about cells and cell theory, but what cell theory explains is the common question asked. Living beings always need nutrition to use energy, grow, reproduce, and live. We react and respond to harmful chemicals and viruses while adapting to changing environments. These activities take place in small units of the body called cells. Life forms in single cells, but most species are multicellular organisms.
Cell theory was unknown until the invention of the microscope. With the help of a microscope, scientists discovered that human and animal bodies are made of active small cells which help the growth of living beings. Cell theory plays a crucial role for all living beings as cells are the basic units of life. They are known as the smallest part of the body, capable of performing all of life’s functions. They grow according to food habits and climatic changes. Groups of cells form tissues, organs, and organisms.
Cell theory, which came into existence in the late 19th century, has three main parts. The first says that all living beings are made up of cells, the second says that all cells are the building blocks of life, which means that a combination of one and more cells form large blocks called tissues. The third part states that all cells have preexisting cells, and each cell created was the process of cell division.
As science evolved, new inventions emerged, and three more components were added to the cell theory:
- Energy flow occurs in cells.
- Hereditary or genetic disorders or genetically passed qualities are generated and take birth inside cells.
- All cells have the same basic composition and are spread throughout the body.
Origin, Concept, and Development of Cell Theory
Cell theory, also known as cell biology, came into existence with the invention of the microscope. In the late 17th century, Robert Hooke used a microscope and found that human and animal bodies consisted of small particles which were modified and called cells. With continuous improvement and inventions, new findings emerged. Hooke’s theory was supported by Matthias Schleiden and Theodor Schwan, who studied cell theory on animals and plants and discovered that there is a significant difference between two types of cells and that they are fundamental to plants and animals.
The Nature of Cells
A cell has a thin layer called a membrane to protect it from external factors like carbon dioxide, viruses, and other chemicals that may damage it. The membrane acts as a filter for the cell’s soft part. The interior is divided into different compartments–each supported by a single membrane–and includes a fluid of genes, blood, etc. These are called organelles and contain a specialised structure comprising nutrients, proteins, and bacteria that help grow and reproduce. A separate membrane surrounds the organelle, and a major organelle is the nucleus, which is necessary for development.
Human cells contain only one nucleus, whereas other types of organelles contain multi organelles, which are also called cytoplasm. Cytoplasm is a fluid of memory and muscle movement. The cell contains special types of molecules that are closed by the membrane, and the whole molecule helps cells grow and recuperate the animal and human body. Active cells grow quickly, and this helps cells in the function of growing and dividing.
Types of Cells
There are an unlimited number of species, and each has different types and natures, which grow and change frequently and have a variety of fluctuations. The commonly known types are called unicellular and multicellular, as follows:
This species, also termed unicellular or single-celled organisms, is the oldest and simpler type. They are not commonly found and are mostly present in bacteria like algae and archaebacteria. They have a cell membrane with one or more additional layers for protection from the outside environment. These cells are made of a cell wall of rigid sugar, and a layer of thick sugar called a capsule which controls movement. When these cells are ready for reproduction, they make a copy of single chromosomes. They then split half of the chromosome into further small parts, and these cells are called daughter cells.
These cells are most commonly found and also called multicellular cells. Found in all living beings like plants, animals, and humans, eukaryotic cells have the capacity to function together to form multicellular organisms. They have multi chromosomes and many genetic tissues within the body. They are independent, and growth and reproduction occur within a single body.
Cell theory is a classical theory, but it has been repeatedly modified with continuous study and the advancement of science and technology. Cells continuously evolve as new technologies emerge and new information gets collected. SScientists proposed the modern cell theory with three salient findings upon further research:
- DNA travels between cells during cell division.
- The cell is the smallest part and is equal in all species.
- Cells are designed chemically and structurally, and energy flows within the cell.
Cell theory states the origin and existence of life and the body structure of every living being. Hence, cell theory plays a very important role in understanding the human body.