The ABCs of AHAs

This is a list of definitions for some of the more technical and scientific words and phrases used in this text, provided as general information.

Aliphatic—An organic compound in which carbon atoms are joined together in straight or branched chains.

Antigen—Any substance foreign to the body that evokes an immune response either alone or after forming a complex with a larger molecule (as a protein) and that is capable of binding with a product of the immune response.

Carboxylic acids—Organic acids characterized by the presence of a carboxyl group.

Ceramide biosynthesis—The production of a chemical compound by a living organism.

Corneocyte cohesion—When dead stratum corneum (SC) cells unite in a large mass in the epidermis.

Cyclin—Any of a group of proteins active in controlling the cell cycle and in initiating DNA synthesis.

Dermal fibroblasts—A connective tissue cell that secretes proteins and collagen from which the extracellular matrix (ECM) forms.

Erythema—Normal redness of the skin due to capillary congestion.

Extracellular matrix—Complex network of polysaccharides (such as glycosaminoglycans or cellulose) and proteins (such as collagen) secreted by cells; a structural component of tissues that also influences their development and physiology.

Follicular hyperkeratosis—Excessive development of the follicles in the corneous layer of the skin.

Glycosaminoglycans—Any of various polysaccharides derived from an amino hexose that are constituents of mucoproteins, glycoproteins and blood-group substances. They form an important component of connective tissues.

Hydrophilic—Relating to, or having a strong affinity for, water.

Hyperplasia—An abnormal or unusual increase in the elements composing a part (as cells composing a tissue).

Immunocompetent cells—Cells that have the capacity for a normal immune response.

Keratinocytes—Major cell type of the epidermis, making up about 90% of epidermal cells.

Krebs cycle—Sequence of reactions in a living organism that provides energy for storage.

Langerhans cells—A cell found in the epidermis that functions as an antigen-presenting cell that binds antigens entering through the skin.

Lamellar ichthyosis—More commonly known as the “fish skin” skin disease, the condition causes the dry skin to resemble fish scales.

Lipase—An enzyme that chemically decomposes glycerides and permits useful energy to be released (as in metabolism).

Melanocytes—An epidermal cell that produces melanin.

Peptide chains—A chain of short molecules formed from the linking, in a defined order, of various amino acids.

Pigmentation morbidity—An undesired coloring of the skin, hair or nails.

Proteoglycan—Any of a class of glycoproteins, which are macromolecules composed of a protein and a carbohydrate, that have a high molecular weight, found especially in the extracellular matrix (ECM) of connective tissue.

Serine biosynthesis—The production of a chemical compound by a living organism.

Steric—Involving the arrangements of atoms in space.

Stratum corneum(SC)—The outermost layer of the epidermis, composed mainly of dead cells that lack nuclei.

Tumorigenesis—Producing or tending to produce tumors.