Category: Biology Dictionary E

Definition Eubacteria, or “true” bacteria, are single-celled prokaryotic microorganisms that have a range of characteristics and are found in various conditions throughout all parts of the world. All types of bacteria fall under this title, except for archaebacteria. Since eubacteria are so common, this group comprises one of the three domains of life: Bacteria. Overview […]

Definition Essential amino acids (EAAs) make up a group of nine amino acids that cannot be produced inside the body (de novo) but must be ingested as dietary protein. The building blocks of proteins, amino acids are bound together to produce polymer chain or folded proteins with a huge array of functions. There are three […]

Esophagus Definition The esophagus (a.k.a. oesophagus, food pipe, and gullet) is a long, hollow organ which transports food from the mouth to the digestive system. Typically, the esophagus travels directly from the mouth to the digestive tract. Some animals do not have a specialized stomach region, and the esophagus dumps directly into the intestines. In […]

Equilibrium Constant Definition An equilibrium constant, Keq, is a variable that describes a chemical reaction’s tendency to proceed to completion, meaning all the reactants are converted to products. The equilibrium of a reaction is the point at which the conversion of reactants into products equals the conversion of products back into reactants. Equilibrium Constant Overview A large […]

Epithelial Tissue Definition Epithelial tissues are thin tissues that cover all the exposed surfaces of the body. They form the external skin, the inner lining of the mouth, digestive tract, secretory glands, the lining of hollow parts of every organ such as the heart, lungs, eyes, ears, the urogenital tract, as well as the ventricular […]

Epistasis Definition Epistasis is the interaction between genes that influences a phenotype. Genes can either mask each other so that one is considered “dominant” or they can combine to produce a new trait. It is the conditional relationship between two genes that can determine a single phenotype of some traits. At each locus are two […]

Enzyme Substrate Complex Definition The enzyme substrate complex is a temporary molecule formed when an enzyme comes into perfect contact with its substrate. Without its substrate an enzyme is a slightly different shape. The substrate causes a conformational change, or shape change, when the substrate enters the active site. The active site is the area […]

Energy Pyramid Definition An energy pyramid (sometimes called a trophic pyramid or an ecological pyramid) is a graphical representation, showing the flow of energy at each trophic level in an ecosystem. The width of each bar represents the units of energy available within each trophic level; the height is always the same. The flow of energy moves […]

Endothelium Definition The endothelium is a layer of cells that lines the blood vessels and lymph vessels of the body. Although you probably don’t know it exists, your epithelium is vital to keeping you alive! It includes all blood-and-lymph carrying vessels, including the chambers of the heart and the glomeruli, or “filters,” of the kidneys. […]

Endosymbiotic Theory Definition Endosymbiotic theory is the unified and widely accepted theory of how organelles arose in organisms, differing prokaryotic organisms from eukaryotic organisms. In endosymbiotic theory, consistent with general evolutionary theory, all organisms arose from a single common ancestor. This ancestor probably resembled a bacteria, or prokaryote with a single strand of DNA surrounded by a plasma membrane. […]