0.5 Glossary  (Page 5/18)

E

• E (exit) site functional site of an intact ribosome that releases dissociated uncharged tRNAs so that they can be recharged with free amino acids
• East African trypanosomiasis acute form of African trypanosomiasis caused by Trypanosoma brucei rhodesiense
• eastern equine encephalitis serious, but rare, mosquito-borne viral infection of the brain that is found primarily on the Atlantic and Gulf coast states of the United States
• Ebola virus disease (EVD) potentially fatal viral hemorrhagic fever found primarily in western Africa and transmitted through contact with body fluids
• eclipse phase period after viral infection during which the infective virus is not detected, either intracellularly or extracellularly, and biosynthesis is occurring
• ectoplasm outer, more gelatinous layer of cytoplasm under a protist cell membrane
• edema swelling due to accumulation of fluid and protein in tissue as a result of increased permeability of capillary walls during an inflammatory response; chronic edema can also result from blockage of lymphatic vessels, as in the case of elephantiasis
• effector cells activated cells of cellular immunity that are involved in the immediate immune response, primarily to defend the body against pathogens
• electron carrier cellular molecule that accepts high-energy electrons from reduced molecules like foods and later serves as an electron donor in subsequent redox reactions
• electron microscope a type of microscope that uses short-wavelength electron beams rather than light to increase magnification and resolution
• electron transport system (ETS) series of membrane-associated protein complexes and associated mobile accessory electron carriers important in the generation of the proton motive force required for ATP production by chemiosmosis; the last component involved in the cellular respiration of glucose
• electroporation a genetic engineering technique in which cells are exposed to a short electric pulse, inducing them to take up DNA molecules from their environment
• elementary bodies metabolically and reproductively inactive, endospore-like form of intracellular bacteria that spreads infection outside of cells
• elongation in DNA replication stage of DNA replication during which DNA polymerase adds nucleotides, complementary to the parental strand, to the 3’ end of a growing DNA strand
• elongation in transcription stage of transcription during which RNA polymerase extends the RNA molecule by adding RNA nucleotides, complementary to the template DNA strand
• elongation of translation stage of translation during which amino acids are added one by one to the C-terminus of the growing polypeptide
• Embden-Meyerhof-Parnas (EMP) pathway type of glycolysis found in animals and the most common in microbes
• emerging infectious disease a disease that is new to the human population or has increased in prevalence over the previous 20 years
• enantiomers stereoisomers that are mirror images of each other and nonsuperimposable
• encephalitis inflammation of the tissues of the brain
• encystment the process of forming a cyst
• endemic disease an illness that is constantly present (often at low levels) in a population
• endergonic reaction chemical reaction that requires energy beyond activation energy to occur
• endocarditis inflammation of the endocardium, especially the heart valves
• endocrine function refers to a cytokine signal released from a cell and carried by the bloodstream to a distant recipient cell
• endocytosis the uptake of molecules through plasma membrane invagination and vacuole/vesicle formation
• endomembrane system a series of organelles (endoplasmic reticulum, Golgi apparatuses, lysosomes, and transport vesicles) arranged as membranous tubules, sacs, and disks that synthesize many cell components
• endoplasm inner, more fluid layer of cytoplasm under a protist cell membrane (inside of the ectoplasm)
• endoplasmic reticulum part of the endomembrane system that is an interconnected array of tubules and flattened sacs with a single lipid bilayer that may be either rough or smooth; important in synthesizing proteins and lipids
• endospore a cellular structure formed by some bacteria in response to adverse conditions; preserves DNA of the cell in a dormant state until conditions are favorable again
• endospore staining a differential staining technique that uses two stains to make bacterial endospores appear distinct from the rest of the cell
• endosymbiotic theory the theory that mitochondria and chloroplasts arose as a result of prokaryotic cells establishing a symbiotic relationship within a eukaryotic host
• endothelia layer of epithelial cells lining blood vessels, lymphatics, the blood-brain barrier, and some other tissues
• endotoxin lipid A component of lipopolysaccharides in the outer membrane of gram-negative bacteria
• enriched media media that contain additional essential nutrients to support growth
• enrichment culture media providing growth conditions that favor the expansion of an organism present in low numbers
• enteric bacteria of the family Enterobacteriaceae, which live in the human intestinal tract
• enteritis inflammation of the lining of the intestine
• enterobiasis intestinal infection caused by the pinworm Enterobius vermicularis
• enterohemorrhagic E. coli (EHEC) E. coli bacteria that cause severe gastrointestinal illness with potential serious complications such as hemolytic uremic syndrome
• enteroinvasive E. coli (EIEC) E. coli bacteria that cause relatively mild gastrointestinal illness
• enteropathogenic E. coli (EPEC) E. coli bacteria that cause serious gastrointestinal illness
• enterotoxigenic E. coli (ETEC) E. coli bacteria that cause a relatively mild illness commonly called traveler’s diarrhea
• enterotoxin toxin that affects the intestines
• Entner-Doudoroff (ED) pathway alternative glycolytic pathway used by some bacteria
• enveloped virus a virus formed with a nucleic-acid packed capsid surrounded by a lipid layer
• enzyme catalyst for biochemical reactions inside cells
• enzyme immunoassay (EIA) type of assay wherein an enzyme is coupled to an antibody; addition of a chromogenic substrate for the antibody allows quantification or identification of the antigen bound by the antibody
• enzyme-linked immunosorbent assay (ELISA) specialized form of EIA in which either the primary antibody or the antigen is first attached to a solid surface such as the well of a microtiter plate
• eosinophils leukocytes with granules containing histamine and major basic protein; facilitate allergic responses and protection against parasitic protozoa and helminths
• epidemic disease an illness with a higher-than-expected incidence in a given period within a given population
• epidemic typhus severe and sometimes fatal infection caused by Rickettsia prowazekii and transmitted by body lice
• epidemiology the study of where and when infectious diseases occur in a population and how they are transmitted and maintained in nature
• epidermis the outermost layer of human skin
• epididymis coiled tube that collects sperm from the testes and passes it on to the vas deferens
• epididymitis inflammation of the epididymis caused by a bacterial infection
• epigenetic regulation chemical modification of DNA or associated histones to influence transcription
• epiglottis flap of cartilage that covers the larynx during swallowing; diverts food to the esophagus and prevents it from entering the respiratory tract
• epiglottitis inflammation of the epiglottis
• epiphyte a plant that grows on another plant
• epitope smaller exposed region on an antigen that is recognized by B-cell and T-cell receptors and antibodies
• Epsilonproteobacteria class of Proteobacteria that are microaerophilic
• equivalence zone region where the antibody–antigen ratio produces the greatest amount of precipitin in a precipitin reaction
• erysipelas a skin infection, typically caused by Streptococcus pyogenes , that presents as a red, large, intensely inflamed patch of skin involving the dermis, usually with clear borders, typically on the legs or face
• erythema nodosum a condition that causes inflammation in the subcutaneous fat cells of the hypodermis resulting in red nodules
• erythema redness at the site of inflammation, usually due to dilation of blood vessels in the area to help bring in white blood cells
• erythrocyte red blood cell
• erythrogenic toxin exotoxin produced by some strains of Streptococcus pyogenes ; activity of the toxin can produce the characteristic rash of scarlet fever
• erythromycin protein synthesis inhibitor of the macrolide class that is often used as an alternative to penicillin
• eschar a localized mass of dead skin tissue
• Etest simple, rapid method for determining MIC, involving commercially available plastic strips that contain a gradient of an antimicrobial and are placed on an agar plate inoculated with a bacterial lawn
• etiologic agent the pathogen or substance responsible for causing a particular disease; causative agent
• etiology the science of the causes of disease
• Eukarya the domain of life that includes all unicellular and multicellular organisms with cells that contain membrane-bound nuclei and organelles
• eukaryote an organism made up of one or more cells that contain a membrane-bound nucleus and organelles
• eukaryotic cell has a nucleus surrounded by a complex nuclear membrane that contains multiple, rod-shaped chromosomes
• eustachian tube small passage between the nasopharynx and the middle ear that allows pressure to equalize across the tympanic membrane
• eutrophs microorganisms that require a copious amount of organic nutrients; also called copiotrophs
• excystment the process of emerging from a cyst
• exergonic reaction chemical reaction that does not require energy beyond activation energy to proceed; releases energy when the reaction occurs
• exocytosis the release of the contents of transport vesicles to the cell’s exterior by fusion of the transport vesicle’s membrane with the plasma membrane
• exoenzyme secreted enzyme that enhances the ability of microorganisms to invade host cells
• exon protein-coding sequence of a eukaryotic gene that is transcribed into RNA and spliced together to code for a polypeptide
• exonuclease enzymatic activity that removes RNA primers in DNA introduced by primase
• exotoxin biologically active product that causes adverse changes in the host cells
• experimental epidemiology the use of laboratory and clinical studies to directly study disease in a population
• experimental study a type of scientific study that involves manipulation of the study subjects by the researcher through application of specific treatments hypothesized to affect the outcome while maintaining rigorously controlled conditions
• exposure contact between potential pathogen and host; also called contamination or contact
• extended-spectrum β-lactamases (ESBLs) β-lactamases carried by some gram-negative bacteria that provide resistance to all penicillins, cephalosporins, monobactams, and β-lactamase-inhibitor combinations, but not carbapenems
• extensively drug resistant Mycobacterium tuberculosis (XDR-TB) strains of M. tuberculosis that are resistant to rifampin and isoniazid, and also are resistant to any fluoroquinolone and at least one of three other drugs (amikacin, kanamycin, or capreomycin)
• extracellular matrix material composed of proteoglycans and fibrous proteins secreted by some eukaryotic cells that lack cell walls; helps multicellular structures withstand physical stresses and coordinates signaling from the external surface of the cell to the interior of the cell
• extracellular polymeric substances (EPS) hydrated gel secreted by bacteria in a biofilm containing polysaccharides, proteins, nucleic acids, and some lipids
• extrachromosomal DNA additional molecules of DNA distinct from the chromosomes that are also part of the cell’s genome
• extravasation process by which leukocytes pass through capillary walls to reach infected tissue; also called diapedesis