Science / Biology Glossary

Electron Acceptor: A molecule that forms part of the electron transport system that transfers electrons ejected by chlorophyll during photosynthesis. Part of the energy carried by the electrons is transferred . . . View Full Definition

Electron Transport: 1) A series of coupled oxidation/reduction reactions where electrons are passed like hot potatoes from one membrane-bound protein/enzyme to another before being finally attached to a termina . . . View Full Definition

Electrostatic Attraction: The attraction between atoms of opposite charge that holds the atoms together in ionic bonds.

Element: A substance composed of atoms with the same atomic number; cannot be broken down in ordinary chemical reactions.

Elongation: During protein synthesis, the growth of the polypeptide chain through the addition of amino acids; the second step in translation.

Embryo: Term applied to the zygote after the beginning of mitosis that produces a multicellular structure.

Embryo Sac: Alternate term applied to the angiosperm female gametophyte contained within a megaspore.

Emphysema: Lung disease characterized by shortness of breath, often associated with smoking.

Endergonic: Chemical reactions that require energy input to begin.

Endochondral Ossification: The process by which human bones form from cartilage.

Endocrine System: One of eleven major body organ systems in animals; a system of glands that works with the nervous system in controlling the activity of internal organs, especially the kidneys, and in coordi . . . View Full Definition

Endocytosis: The incorporation of materials from outside the cell by the formation of vesicles in the plasma membrane. The vesicles surround the material so the cell can engulf it.

Endoderm: The inner layer of cells in embryonic development that gives rise to organs and tissues associated with digestion and respiration. Also, the inner tissue layer in fiatworms.

Endodermis: A layer of cells surrounding the vascular cylinder of plants.

Endometrium: The inner lining of the uterus.

Endoplasmic Reticulum (ER): A network of membranous tubules in the cytoplasm of a cell; involved in the production of phospholipids, proteins, and other functions. Rough ER is studded with ribosomes; smooth ER is not.

Endoskeleton: An internal supporting skeleton with muscles on the outside; in vertebrates, consists of the skull, spinal column, ribs, and appendages.

Endosperm: A food storage tissue that provides nutrients to the developing embryo in angiosperms; formed from the triploid cell produced when a sperm cell fertilizes the central cell. Some endosperm is . . . View Full Definition

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