You will have learned at KS3 about the basic structure of a “typical” animal cell. But our bodies are not made of cells that look like this “typical” cell. Humans have just over 200 different types of cell, each specialised to carry out a particular function. For example red blood cells are specialised for transporting oxygen, muscle cells are specialised for movement and sperm cells are specialised as the male gamete for delivering a haploid nucleus to the egg cell.
The diagram above shows examples of a few types of specialised cells from the human body.
These specialised cells are produced in the process of cell division.
Cells that are not yet specialised but that retain the ability to develop into a variety of different cell types are called stem cells. Many cells in the embryo are stem cells (as they have not yet specialised into a particular cell type) but we also have a few stem cells in the adult (for example the cells in the bone marrow that can develop into all the different cell types in blood).
The process by which stem cells develop into specialised cells is called differentiation. Luckily you don’t need to understand exactly how this works but basic idea is this: differentiation involves certain genes in the nucleus being switched on and off so that a specialised cell only makes a certain set of proteins. Remember that a gene is a section of our DNA that codes for a single protein. Nerve cells make the proteins needed to send nerve impulses, white blood cells make the proteins needed to combat infections. You get the idea…..
Stem cells play an important role in medicine but that’s for another post……… If you want to read more about stem cells, this website is a good place to start.