Acid lipase -- An enzyme of the hydrolase class produced by glands on the tongue and by the pancreas. It starts the digestion of dietary fats by catalyzing the reaction of triacylglycerol and water to yield diacylglycerol and a fatty acid anion (a negatively charged ion).

Cholesterol -- A white crystalline substance found in animal tissues and various foods that is normally synthesized by the liver and is important as a constituent of cell membranes and a precursor to steroid hormones. Its level in the bloodstream can influence the development of certain conditions, such as the development of atherosclerotic plaque and coronary artery disease.

Coronary artery disease -- The thickening and loss of elasticity of the arteries that flow into the heart, leading to progressive insufficiency of the arteries.

DNA, or deoxyribonucleic acid -- The primary genetic material of all cellular organisms and the DNA viruses. Located predominantly in cell nuclei, it is composed of two chains of nucleotides--deoxyribose and phosphate backbones with side chains of purine (adenine or guanine) or pyrimidine (cytosine and thymine) bases projecting inward. Hydrogen bonds link adenine to guanine, and cytosine to thymine. The two linked strands are twisted in a double helix.

Dyslipoproteinemia -- The presence of abnormal concentrations of lipoproteins, or of abnormal lipoproteins, in the blood. Tangier disease is an example of an inherited form of dyslipoproteinemia.

Escherichia coli, or E. coli -- A common bacterium that has been studied intensively by geneticists because of its small genome size, normal lack of pathogenicity, and ease of culture in the laboratory.

Fatty acid -- A long chain of aliphatic carboxylic acid (organic, monobasic acids derived from hydrocarbons) found in natural fats and oils, it is also a component of membrane phospholipids and glycolipids.

Genetic engineering -- The group of applied techniques of genetics and biotechnology used to cut and join together genetic material and especially DNA from one or more species of organism and to introduce the result into another organism in order to change one or more of its characteristics. Also a popular term for recombinant DNA technology.

Genotype -- The specific allelic composition of a cell, either of the entire cell or more commonly for a certain gene or a set of genes. Also, the genes an organism possesses.

High-density lipoprotein cholesterol (HDLC) -- The portion of plasma lipoprotein cholesterol with most density. It is believed to affect blood cholesterol levels by removing cholesterol from plasma and tissues and carrying it back to the liver for action by bile and eventual excretion. High levels of HDLC are considered to place an individual at a lower risk for coronary heart disease; low levels of HDLC are associated with an increased risk for the disease.

Lipid -- A small water-insoluble biomolecule generally containing fatty acids, sterols, or isoprenoid compounds.

Low-density lipoprotein cholesterol (LDLC) -- The protein-lipid combination that transports the major amount of the cholesterol in the blood. While LDLC helps in synthesis of bile acid and steroid hormones, elevated blood levels of LDLC--or "bad cholesterol"--have been linked to heart disease because it carries the cholesterol through the blood to the cells.

Metabolism -- The chemical reactions occurring in a living cell which provide energy for vital processes and activities, and assimilate new material.

Molecular biology -- The branch of biology dealing with the formation, structure, and function of macromolecules essential to life, such as DNA, RNA, and proteins, especially their role in cell replication and the transmission of genetic information.

Nucleotide -- A unit that polymerizes into nucleic acids (DNA or RNA). Each nucleotide consists of a purine (adenine or guanine) or pyrimidine (cytosine, thymine, or uracil) base, a sugar (ribose in the case of RNA, deoxyribose in the case of DNA), and a phosphate molecule.

Pathogen -- An organism that causes disease in another organism.

Phenotype -- The observable outward physical or biochemical characteristics of a specific genotype.

Plasma proteins -- Proteins present in blood serum, including serum albumin, blood coagulation factors, and many other types of proteins.

Protein chemistry -- A branch of chemistry which encompasses a range of techniques and approaches that can aid the investigation of protein structure and function.

Recombinant DNA, rDNA, hybrid strings -- Genetically engineered DNA prepared in vitro by cutting up DNA molecules and splicing together specific DNA fragments, usually from more than one type of organism, e.g., inserting pieces of virus DNA into a bacterial plasmid.

RNA, or ribonucleic acid -- A single-stranded nucleic acid found in the cell nucleus and cytoplasm, which plays a key role in protein synthesis. (It also constitutes the genetic material of the RNA viruses.) It is similar to DNA but has ribose sugar, rather than deoxyribose sugar, and uracil, rather than thymine, as one of the pyrimidine bases. There are several classes of RNA molecules, including messenger RNA, transfer RNA, and ribosomal RNA, each serving a different purpose in the cell.

Tangier disease -- An inherited lipoprotein deficiency caused by a decreased synthesis and increased catabolism of the apolipoprotein components a-I and a-II of high-density lipoproteins, or HDL. HDL is absent from plasma, and the other lipoproteins are abnormal; cholesteryl esters accumulate in the reticuloendothelial cells. It is also called analphalipoproteinaemia and Familial High-Density Lipoprotein Deficiency. It was named for the island in the Chesapeake Bay where the first cases were identified.

Tonsils -- A small oral mass of lymphoid tissue, such as the two masses embedded in the lateral walls of the opening between the mouth and the pharynx. Their function is uncertain, but they are believed to help protect the body from respiratory infections.