GLOSSARY OF TERMS

Epithelial tissue acts as a covering and lining on the outside surfaces of the body and lines the internal organs or secretes hormones or other products.

Glossary

Absorption: the process in which nutrients enter cells of the villi, then move across the cells and enter blood vessels.

Acetylcholinesterase, also known as AChE, is an enzyme that degrades (through its hydrolytic activity) the neurotransmitter acetylcholine, producing choline and an acetate group. It is mainly found at neuromuscular junctions and cholinergic synapses in the central nervous system, where its activity serves to terminate synaptic transmission.

Actin: a protein filament within the sarcomeres of muscle cells.

Adhesin: A molecular component of the surface of a microorganism that is involved in adhesion to a substratum or cell. Adhesion to a specific host tissue usually is a preliminary stage in pathogenesis, and adhesins are important virulence factors.

Aerobe: An organism that grows in the presence of atmospheric oxygen.

Aflatoxin: A polyketide secondary fungal metabolite that can cause cancer.

Algicide: An agent that kills algae.

Alleles: Alternative forms of a genetic characteristic.

Anabolism: the process of synthesizing large molecules by joining smaller molecules together.

Anaerobic: organisms that thrive in an oxygen-free environment.

Anaphase: stage in mitosis and meiosis where chromosomes begin moving to opposite ends (poles) of the cell.

Annotation: The process of determining the location of specific genes in a genome map after it has been produced by nucleic acid sequencing.

Antagonistic hormones: hormones that act to return body conditions to within acceptable limits from opposite extremes.

Antigen: any molecule, usually a protein or polysaccharide, that can be identified as foreign or nonself. It may be a toxin, or a part of the protein coat of a virus, or a molecule unique to the plasma membranes.

Aquaculture – the farming of marine and fresh water organisms.

Atoll – a coral reef that develops as a ring around a central lagoon.

Autosome: All chromosomes except those involved in sex determination.  Humans have 22 pairs of autosomes and the X and Y sex chromosomes (XX for females, YY for males).

Axon: the long extension of a neuron.

Basophils: the white blood cells that function in allergic responses.

Bioaccumulation: the process whereby pollutants are taken up, retained and concentrated in the cells of plants and animals.

Bioluminescence – the production of light by living organisms.

Biomass: the total dry weight of food at each level of the food pyramid.

Bowman's capsule: an enlarged cuplike structure below the nephron in the human kidney.

Chemosynthesis: The process whereby chemical energy is used to make organic compounds from inorganic compounds. One example is the oxidation of ammonia to nitrite by nitrifying bacteria.

Chromatid: homologous chromosomes joined to each other at the centromere; present during the prophase of mitosis.

Cistron: A length of chromosomal DNA representing the smallest functional unit of heredity, essentially identical to a gene.

Cofactor: The nonprotein component of an enzyme; it is required for catalytic activity.

Cones: photoreceptor cells that respond to bright light and color and transmit sharp images.

Cristae: the folds of the inner mitochondrial membrane.

Cytochromes: molecules that accept and release electrons in an electron transport system.

Cytokinesis: is the process in which the cytoplasm of a single eukaryotic cell is divided to form two daughter cells.

Cytosol: a fluid matrix of water and dissolved substances such as proteins and nutrients.

Dermis: the second layer of skin.

Diastole: a relaxation event of either the atria or ventricles.

Diencephalon: connects the cerebrum to the brain stem.

Diploid: Having a full set of genetic material consisting of paired chromosomes. One of each pair of chromosomes comes from each parent.

Diffusion: the net movement of substances from an area of higher concentration to an area of lower concentration.

Disaccharide: a carbohydrate consisting of two linked sugar molecules.

Double Helix: term used to describe the structure of DNA.

Ectoderm: one of three germ layers that develops into the skin and nervous system.

Effluent: Industrial or urban waste discharged into the environment.

Electrophoresis: A method of separating large molecules-such as DNA fragments or proteins-from a mixture of similar molecules.

Endolymph: is the fluid contained in the membranous labyrinth of the inner ear. It is also called Scarpa's fluid, after Antonio Scarpa.

Entropy: the degree of disorder or randomness of a system.

Enzyme: A protein that acts as a catalyst, speeding the rate at which a biochemical reaction proceeds but not altering the direction or nature of the reaction. All cellular metabolism is controlled by enzymes.

Erythrocytes: the red blood cells; disk-shaped cells produced in the bone marrow that have no nucleus; their cytoplasm is filled with hemoglobin to transport oxygen.

Eubacteria: modern bacteria

Eutrophication: Enrichment of a water body with nutrients, resulting in excessive growth of phytoplankton seaweeds, or vascular plants, and often depletion of oxygen.

Exon: A segment of a gene that contains instructions for making a protein. In many genes the exons are separated by "intervening" segments of DNA, known as introns, which do not code for proteins; these introns are removed by splicing to produce messenger RNA.

Flagella: structure that protrudes from the cell membrane and makes wavelike movements. Classified by length and number per cell, flagella are long and few. A single flagellum propels sperm. Structurally flagella consists of microtubules arranged in a "9 + 2" array.

Gametangium: A structure that contains gametes or in which gametes are formed.

Ganglia: clusters of cell bodies in the peripheral nervous system.

Genome: The full set of genes present in a cell or virus; all the genetic material in an organism; a haploid set of genes in a cell.

Glomerulus: a ball of capillaries that comprises Bowman's capsule in the human kidney.

Glucagon: a hormone produced in the pancreas that stimulates the breakdown of glycogen to glucose in the liver.

Glycogen: A highly branched polysaccharide containing glucose, which is used to store carbon and energy.

Gross (macroscopic) anatomy: the study of body parts visible to the naked eye.

Guanine: A purine derivative, 2-amino-6-oxypurine, found in nucleosides, nucleotides, and nucleic acids.

Halophile: A microorganism that requires high levels of sodium chloride for growth.

Haploid: A cell with half the usual number of chromosomes, or only on chromosome set.  Sex cells are haploid.

Hapten: a molecule not immunogenic by itself but that, when coupled to a macromolecular carrier, can elicit antibodies directed against itself.

Helicases: Enzymes that use ATP energy to unwind DNA ahead of the replication fork.

Hemopoiesis: the process that produces the formed elements of the blood and takes place in the red bone marrow of long bones.

Histology: the study of tissues at the microscopic level.

Holdfast: A structure produced by some bacteria and algae that attaches the cell to a solid object.

Holoenzyme: A complete enzyme consisting of the apoenzyme plus a cofactor.

Homologies: Similarities in DNA or protein sequences between individuals of the same species or among different species.

Hypodermis: the layer between the dermis and the underlying tissues and organs.

Hypha: The unit of structure of most fungi and some bacteria; a tubular filament.

Hypoxic: Having a low oxygen level.

Inducer: A small molecule that stimulates the synthesis of an inducible enzyme.

Insertion: the muscle end that attaches to the moving structure.

Isogenic: Of the same genotype.

Intron: A noncoding intervening sequence in a split or interrupted gene, which codes for RNA that is missing from the final RNA product.

Karyotype: A photomicrograph of an individual's chromosomes arranged in a standard format showing the number, size, and shape of each chromosome type.

Limbic System: a network of neurons that extends over a wide range of areas of the brain. Imposes an emotional aspect to behaviors, experiences, and memories.

Lipids: a class of substances that are insoluble in water (and other polar solvents) but are soluble in nonpolar substances (like ether or chloroform).

Liposome: A spherical particle formed by a lipid bilayer enclosing an aqueous solution.  It may be use to administer chemotherapeutic agents or in diagnostic testing.

Lymph: a watery fluid derived from plasma that seeps out of the blood system capillaries and mingles with the cells.

Lymphocytes: white blood cells (leukocytes) that provide an immune response that attacks specific kinds of nonself cells and foreign substances.

Lysis: Breaking apart of cells.

Lysogeny: The state in which a phage genome remains within the baterial host cell after infection and reproduces along with it rather than taking control of the host and destroying it.

Macronucleus: The larger of the two nuclei in ciliate protozoa. It is normally polyploid and directs the routine activities of the cell.

Macrophage (mak_ro-føaj)  The name for a large mononuclear phagocytic cell, present in blood, lymph, and other tissues. Macrophages are derived from monocytes. They phagocytose and destroy pathogens; some macrophages also activate B cells and T cells. 

Mesenchyme: or mesenchymal connective tissue, is an example of reticular connective tissue, a type of loose connective tissue, which is derived from all three germ layers and located within the embryo.

Metastasis: The transfer of a disease like cancer from one organ to another not directly connected with it.

Metamorphosis: is a biological process by which an animal physically develops after birth or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and differentiation.

Monera: the kingdom that includes the bacteria and the cyanobacteria; prokaryotic organisms.

Monophyletic: descended from a common ancestor or stem cell.

Mycoplasma: is a genus of bacteria which lack a cell wall. Without a cell wall, they are unaffected by many common antibiotics such as penicillin or other beta-lactam antibiotics that target cell wall synthesis.

Mycosis: Any disease caused by a fungus.

Phagocytes: white blood cells that wander throughout the body attacking bacteria and other foreign invaders.

Phenotype: The outward physical characteristics of an organism.

Pluripotency: in the broad sense refers to "having more than one potential outcome." In biological systems, this can refer either to cells or to biological compounds. From the Latin pluri=many, potent=power, capacity. A pluripotent cell can create all cell types except for extra embryonic tissue, unlike a totipotent cell, (tot=all), which can produce every cell type including extra embryonic tissue.

Pneumothorax: (a term for collapsed lung) occurs when air leaks into the space between your lungs and chest wall, creating pressure against the lung.

Polymerase: an enzyme that acts like a molecular assembly line to build new strands of DNA.

Polypeptide: A molecule made up of a string of amino acids. A protein is an example of a polypeptide.

Proteins: The active molecules in all cells. Proteins control biochemical reactions and determine the physical structure of organisms.

Ribosome: The small cellular structure in which RNA translates the genetic code into proteins.

Rods: photoreceptors that are most sensitive to light and more numerous than cones. The provide vision in dim light and are more capable of detecting movement.

Septate: Divided by a septum or cross wall; also with more or less regular occurring cross walls.

Sheath: A hollow tubelike structure surrounding a chain of cells and present in several genera of bacteria.

Somatic cells: Any cell in the body except sex cells.

Spirillum: a rigid, spiral-shaped bacterium

Strain: A population of organisms that descends from a single organism or pure culture isolate.

Symbiosome: The final nitrogen-fixing form of Rhizobium that is active within root nodule cells.

Systole: a contraction event of either the atria or ventricles.

Transcription: The process by which DNA passes genetic information to RNA. Transcription is the first step in producing proteins.

Uracil: A base; one of the molecular components of RNA. Bonds only with adenine (U-A).