A poptosis A type of cell death in which the cells are genetically programmed to die, often in developmental programmes such as the loss of webs between fingers in the human hand.

A rchaea Previously classified with bacteria, Archaea are a similar group of primitive single cell organisms that can also live in the most extreme conditions on earth.

A xoneme A central complex of microtubules which supports cell extensions such as the classic 9+2 organization found in cilia and flagellae.

Ciliopathies A group of genetic conditions resulting from defects in cilia, flagellae, or their basal bodies, leading to a variety of different diseases.

Condensation The final packaging of chromosomes at metaphase, prior to separation of chromatids to the daughter cells.

Cytokinesis The last stage of cell division, following nuclear division, when the mother cell cytoplasm is separated into two daughter cells.

Cytoskeleton The combined organization of microtubules, intermediate filaments, and microfilaments, which works together to control cell shape, locomotion, and division.

Dalton The unit of atomic mass, equal to one atom of hydrogen.

Desmosome A specialized region of the cell membrane between adjacent cells in tissue, forming a junction which joins cells together, anchored in the cytoplasm by intermediate filaments.

Diploid Normal amount of DNA in somatic cells, in the form of paired (homologous) chromosomes, in contrast to germline cells (sperm and eggs) which have a single set of chromosomes, and are haploid.

Endosymbiosis The mutually advantageous relationship of previously free-living precursors of mitochondria and chloroplasts with the larger cells they came to live in early in the evolution of eukaryotic cells.

Epithelium Cells that line surfaces in the body. One of the four basic types of tissue that make up the body, along with nervous tissue, muscle tissue, and connective tissue.

Eukaryote A cell with a clearly defined nucleus, enclosed in a membrane, and with other membrane-bound organelles in the cytoplasm.

Exocytosis The release of material from inside the cell, mediated by fusion between vacuolar and plasma membranes, which occurs during secretion of cell products.

Exon A sequence of bases, usually in messenger RNA, ready for translation into a specific protein after the removal of introns during splicing in post transcriptional processing.

Fibroblast A cell found in connective tissue, which secretes collagen and extracellular matrix, and responds to damage by pulling wound margins together.

Gamete A mature sexually reproductive cell (egg or sperm in animals, pollen and ovum in plants) which fuse to from the zygote, the diploid precursor, and ultimate stem cell of every organism.

Gene The unit of heredity, carrying the instructions for production of a specific protein coded in the form of a series of bases in a sequence in DNA.

Haploid　see Diploid.

Intron A sequence of bases removed from a gene during RNA splicing ( see Exon).

Laminopathies A series of rare genetic conditions resulting from mutations in proteins of the nuclear lamina, e.g. Emery-Dreyfus muscular dystrophy.

Lipogenesis The formation of fat from the metabolism of simple sugars.

Millimetres, microns, and nanometres. A millimetre is equal to one thousand microns, and a micron equals one thousand nanometres. A whole eukaryote cell may be 10 microns in diameter, part of that cell, e.g. a microtubule is 25 nanometres in diameter. The diameter of human hair varies between 50 and 100 microns.

Nucleoskeleton An intranuclear network of filamentous proteins, anchored at the nuclear envelope which maintains nuclear integrity and provides a framework for DNA replication and genetic processes.

Oxidative phosphorylation A metabolic pathway in mitochondria that creates adenosine triphosphate (ATP) from the oxidation of nutrients. Energy is stored in ‘high energy’ bonds in ATP.

Phagocytosis Literally ‘cell eating’, where processes that extend from the cell engulf and enclose material which then becomes internalized and contained within a vacuole in the cytoplasm.

Prokaryote A cell lacking an enclosed nucleus; simpler and considerably smaller than a eukaryote. All bacteria are prokaryotes.

Transcription The synthesis of an RNA copy of DNA in the nucleus as the first step towards protein production in the cytoplasm .

Translation The synthesis of proteins from an mRNA template produced by ribosomes in the cytoplasm.

Zygote The result of fusion between gametes, restoring the diploid cell, and the ultimate stem cell from which the whole organism develops.