The bitter-sweet taste of toxic substances
Glossary
enzyme. A protein that acts as a catalyst. Every chemical reaction in living organisms is facilitated by an enzyme.
food chain. A sequence of organisms including plants, herbivores (plant-eating animals) and carnivores (meat-eating animals), through which energy and materials move within an ecosystem.
ion, anion, cation, and divalent ion. An ion is an electrically charged atom or group of atoms. The charge is the result of the loss (positive ion) or gain (negative ion) of one or more electrons.
The gain of one or more electrons produces an ion with a negative charge (anion). The loss of one or more electrons produces an ion with a positive charge (cation). Ions that have gained or lost two electrons are called divalent ions.
LD50 . The amount of a substance that is lethal to 50 per cent of the experimental animals exposed to it. LD50 is usually expressed as the weight of the substance per unit of body weight of the animal in order to account for weight difference among animals. More information about LD50 and other measures of exposure to toxic substances can be found at Dose-response relationships in toxicology (Extension Toxicology Network, 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).
smelter. An industrial plant that uses a high-temperature process to separate out a pure metal, usually in a molten form, from an ore.
Page updated August 2006.