In all living cells, DNA makes RNA and RNA makes proteins. The molecular factory that translates the information from RNA to proteins is called the “ribosome” (shown in the accompanying movie). It is a large and sophisticated entity, itself made of RNA and proteins.

DNA polymerases

Most genes contain the information needed to make functional molecules called proteins. During the process of transcription, the information stored in a gene’s DNA is passed to a similar molecule called RNA (ribonucleic acid) in the cell nucleus.

The information to produce a protein is encoded in the cell’s DNA. When a protein is produced, a copy of the DNA is made (called mRNA) and this copy is transported to a ribosome. Ribosomes read the information in the mRNA and use that information to assemble amino acids into a protein.

In particular, organelles called chloroplasts allow plants to capture the energy of the Sun in energy-rich molecules; cell walls allow plants to have rigid structures as varied as wood trunks and supple leaves; and vacuoles allow plant cells to change size.

Cells are of two types: eukaryotic, which contain a nucleus, and prokaryotic, which do not. Prokaryotes are single-celled organisms, while eukaryotes can be either single-celled or multicellular.

The first cells were most likely primitive prokaryotic-like cells, even more simplistic than these E. coli bacteria. The first cells were probably no more than organic compounds, such as a simplistic RNA, surrounded by a membrane.

A cell consists of three parts: the cell membrane, the nucleus, and, between the two, the cytoplasm. Within the cytoplasm lie intricate arrangements of fine fibers and hundreds or even thousands of miniscule but distinct structures called organelles.

New cells are created from a process called cell division. The new cells are produced when a cell, called the mother cell, divides into new cells called daughter cells. When two daughter cells have the same number of chromosomes as the original cell, the process is called mitosis.