Cellular Basics

Prokaryotic and Eukaryotic Cells

What is the chemical composition of a typical mammalian cell?

The oldest, living cultured human cells are the HeLa cell line, or population of cells. They were the first line of human cells to survive in a test tube (called in vitro) and have been a standard for understanding many human biological processes. All HeLa cells are derived from Henrietta Lacks, a thirty-one-year-old woman from Baltimore, Maryland, who died of cervical cancer in 1951. This culture led to advancements in many areas, such as cancer, HIV/AIDS, and even helped in the development of a polio vaccine in the 1950s. In addition, using this cell line, scientists discovered that 80 to 90 percent of cervical cancers (carcinomas) contain human papillomavirus DNA.

In 2013, scientists did the first detailed sequence of the genome of a HeLa line. Along with discovering many widespread abnormalities in the structure and number of chromosomes, they found other unexpected results. For example, they discovered that regions of the chromosomes in each cell were arranged in the wrong order and had either extra or too few copies of genes. This was a sign of a newly discovered phenomenon called chromosome shattering—one that is associated with about 2 to 3 percent of all cancers.

A typical mammalian cell—such as those for humans, apes, deer, and a plethora of other mammals—can be broken down into its chemical composition. On the average, the following chart lists those chemicals:

Molecular component

Percent of total cell weight





Phospholipids and other lipids


Miscellaneous small metabolites




Inorganic ions (sodium, potassium, magnesium, calcium, chlorine, etc.)







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