Prions morphing agents of disease
DNA (deoxyribonucleic acid). The nucleic acid forming the genetic material of all organisms with the exception of some viruses which have RNA. DNA is present in the nucleus and other organelles such as mitochondria and chloroplasts.
hormone. A substance produced in one part of the body and carried by the blood to another part of the body where it causes a response (eg, insulin, produced by the pancreas, that promotes the uptake of glucose by body cells). For more information see The hormones of the human (Kimball's Biology Pages, USA) and The hormones (Center for Bioenvironmental Research, Tulane and Xavier Universities, USA).
normal prion protein. Special proteins that can change shape and be stable in the new form. Most proteins fold into a particular shape that allows them to perform their function, and if they don't fold into the correct shape they get degraded and the body gets rid of them.
prion. A small proteinaceous infectious particle which resists inactivation by procedures that modify nucleic acid. Most researchers think that prions are the cause of several diseases including scrapie in sheep, bovine spongiform encephalopathy in cattle and kuru and Creutzfeldt-Jakob disease in humans. More information about prions can be found at Prions: Puzzling infectious proteins (National Institutes of Health, USA).
protein. A large molecule composed of a linear sequence of amino acids. This linear sequence is a protein's primary structure. Short sequences within the protein molecule can interact to form regular folds (eg, alpha helix and beta pleated sheet) called the secondary structure. Further folding from interaction between sites in the secondary structure forms the tertiary structure of the protein.
Proteins are essential to the structure and function of cells. They account for more than 50 per cent of the dry weight of most cells, and are involved in most cell processes. Examples of proteins include enzymes, collagen in tendons and ligaments and some hormones. More information can be found at Protein structure and diversity (Molecular Biology Notebook, Rothamsted Research, UK).
Page updated December 2009.