Introduction to Cells — What is a cell? Why do cells divide? How do cells survive? How do cells die?

Wild type Human mast cell line 1 (HMC-1) were high pressure frozen and visualised through transmission electron microscopy (TEM). The images show the nucleus of the cells and the black arrow indicates nuclear envelope budding events. (doi:10.7295/W9CIL50930)

What is a cell?

The cell is the smallest unit of life that can divide, multiply, grow and respond to stimuli from the environment.

Why and how do cells divide?

Cells divide for many reasons. For example, when you skin your knee, cells divide to replace old, dead, or damaged cells. Cells also divide so living things can grow. When organisms grow, it isn’t because cells are getting larger. Organisms grow because cells are dividing to produce more and more cells. In human bodies, nearly two trillion cells divide every day.

Mitosis is the process by which a cell replicates its chromosomes and then segregates them, producing two identical nuclei in preparation for cell division. Mitosis is generally followed by equal division of the cell’s content into two daughter cells that have identical genomes.

Meiosis, on the other hand, is used for just one purpose in the human body: the production of gametes — sex cells, or sperm and eggs. Its goal is to make daughter cells with exactly half as many chromosomes as the…