Why We Study the Cell and Its Components

Cytology, or the study of cells, is necessary to gain a greater understanding of the world around us. Through the use of microscopes we are able to uncover the world on a whole new "spectrum".

Since Robert Hooke examined a slice of cork underneath a microscope, scientists have discovered that every living thing is made up of cells. This discovery led to the cell theory, which states that every living thing is made up of cells and that those cells come from cells (Simon, Dickey, & Reese, 2010). The cell is the basic unit of life.

Through the study of cells, scientists have broken cells down into two major categories; prokaryotic cells and eukaryotic cells.

Prokaryotic cells, which are organisms from the bacteria and archaea, have no nucleus. They Instead they have a nucleoid, a coil of DNA that is not separated from the rest of the cells by membranes. Prokaryotes are single-celled organisms, the simplest form of life. A rigid cell wall invokes the plasma membrane of the majority of prokaryotic cells, protecting the cell and helping it to retain its shape. Some prokaryotes have another layer, or capsule, surrounding the cell wall. Capsules provide protection by helping prokaryotes stick a surface. There are prokaryotes that have short projections, or (pili), that have the ability to attach to a surface. Some prokaryotic cells have a long projection called flagella. These long projections enable them to propel through a liquid environment (Simon, Dickey, & Reese, 2010).

The other category is eukaryotic cells. Eukaryotes include plants, animals and fungi. They are multi-celled organisms that contain a nucleus. Eukaryotic cells have organelles or ("little organs"). These organelles are membrane enclosed and have specific functions. The nucleus is the most important organelle. It houses the majority of the eukaryotic cell's DNA and is enclosed with a double cell membrane.

Once scientists found out that every living thing had cells, they needed to find out more about them. This led to the development of more powerful microscopes that allowed them to see beyond the basic structure of the cell. Microscopes such as the electron, scanning and the transmission electron microscope have done just that.

Having the ability to examine cells more closely has shown that whether prokaryotic or eukaryotic, both cell types contain many of the same components. The common components of both cell types include a cell wall, plasma membrane, cytoplasm, ribosomes and flagella. The cell wall provides rigidity, while the plasma membrane is a selective barrier to the passage molecules in and out of the cell. The cytoplasm is the entire region of the cell between the nucleus and the plasma membrane. Ribosomes consist of RNA and protein and are the site of protein synthesis. Flagella are long appendages that propel protists through