Biology

Robert Hooke in 1665 described his use of a microscope to observe slices of cork from a tree. He claims to have seen small box like compartments that he called ‘cells’. Hooke was credited as the person who discovered cells. In 1674, a Dutch cloth merchant by the name of Anton Van Leeuwenhoek used a simple microscope to observe materials he scraped from between his teeth. He was the first person to observe bacterial cells. Then in 1853, Robert Brown a Scottish botanist named the nucleus organelle. He was the first to introduce the concept of a nucleated cell as the unit of structure in plants although he had no idea about the importance of the nucleus and had some doubt about whether each cell needed one. In 1838, two German biologists (Schwann and Schleiden) suggested that cells were the basic structural unit of all plant matter and that animals were aggregates of cells arranged according to a definite law. After sharing their ideas over dinner in October of 1838, the two biologists came to recognise that both plant and animal tissues have a cellular organisation. The two than came to a conclusion, that “all living things are composed of cells or they developed out of cells”. They also stated in their work (Cell theory) that: “All living things consist of one or more organised structures that are called cells or of products of cells. Cells are the basic functional unit of life.” In 1858, Rudolf Virchow challenged the old theory of Spontaneous Generation with his theory that “New cells are produced from existing cells.” This theory is called Biogenesis and applies to all structures of living organisms.

Cells structure:

Surface: it is the cells outer protective layer which consists of a cell membrane and in some instances a cell wall. The main function of the cells surface is to protect and provide support for the inner organelles and substances.

Cytoplasm: it is the clear, thick jelly like material within a cell (cytosol). Organelles can be found inside its...