0.5 Glossary  (Page 10/18)

J

• Japanese encephalitis arboviral disease caused by the Japanese encephalitis virus (JEV) and endemic to Asia
• jaundice yellowish color of the skin and mucous membranes caused by excessive bilirubin caused by a failure of the liver to effectively process the breakdown of hemoglobin

K

• keratin a fibrous protein found in hair, nails, and skin
• keratitis inflammation of the cornea
• keratoconjunctivitis inflammation of both the cornea and the conjunctiva
• kidney organ that filters the blood, producing urine
• Kinyoun technique a method of acid-fast staining that does not use heat to infuse the primary stain, carbolfuchsin, into acid-fast cells
• Kirby-Bauer disk diffusion test simple, rapid method for determining susceptibility and resistance of a bacterial pathogen to antibacterial drugs. The test involves drug-impregnated disks placed on an agar plate inoculated with a bacterial lawn.
• Koplik’s spots white spots that form on the inner lining of the cheek of patients with measles
• Krebs cycle cyclic pathway during which each two-carbon unit entering the cycle is further oxidized, producing three NADH, one FADH ₂ , and one ATP by substrate-level phosphorylation, releasing two CO ₂ molecules and regenerating the molecule used in the first step; also called the citric acid cycle or the tricarboxylic acid cycle
• kuru rare form of transmissible spongiform encephalopathy endemic to Papua New Guinea

L

• lacrimal duct connects the lacrimal gland to the lacrimal sac
• lacrimal gland a gland situated above the eye that secretes tears
• lacrimal punctum opening in each upper and lower eyelid
• lacrimal sac a to a reservoir for tears; also known as the dacrocyst or tear sac
• lag period the time between antigen exposure and production of antibodies
• lag phase interval before exponential growth of a microbial population during which cells adjust to a new environment
• lagging strand strand of DNA made discontinuously by DNA polymerase
• laryngitis inflammation of the larynx
• laryngopharynx lower portion of the pharynx that connects to the larynx
• larynx region of the respiratory tract containing the vocal cords; also referred to as the voice box
• latent disease disease that goes into a dormant nonreplicative state after the acute disease and can persist in this state for years, with the risk of reactivation back into acute disease
• latent virus virus that remains dormant in the host genome
• lateral flow test see immunochromatographic assays
• leading strand strand of DNA made continuously in the 5’ to 3’ direction by DNA polymerase
• Legionnaires disease atypical pneumonia occurring in older individuals; caused by the inhalation of Legionella pneumophila aerosolized in water
• leishmaniasis protozoan infection caused by Leishmania spp. and transmitted by sand flies
• leprosy see Hansen’s disease
• leptospirosis bacterial infection of the kidney caused by Leptospira spp.; may spread to the liver, lungs, brain, and other organs
• leukocidin class of exotoxin that targets and lyses leukocytes
• leukocytes white blood cells of various types, including granulocytes, lymphocytes, and monocytes
• leukotrienes lipid-based chemical mediators produced by leukocytes and other tissue cells; promote inflammation and allergic responses
• lichen symbiotic association of a fungus with an algae or cyanobacterium
• ligation repair of the sugar-phosphate backbone of the DNA, making the DNA molecule continuous
• light chains the shorter identical peptide chains of an antibody molecule (two per antibody monomer), composed of variable and constant region segments
• light-dependent reaction process by which energy from sunlight is absorbed by pigment molecules in photosynthetic membranes and converted into stored chemical energy in the forms of ATP and NADPH
• light-harvesting complex group of multiple proteins and associated pigments that each may absorb light energy to become excited, and transfer this energy from one pigment molecule to another until the energy is delivered to a reaction center pigment
• light-independent reaction process by which chemical energy, in the form of ATP and NADPH produced by the light-dependent reactions, is used to fix inorganic CO ₂ into organic sugar; usually referred to as the Calvin-Benson cycle
• lincomycin naturally produced protein synthesis inhibitor of the lincosamide class that binds to the 50S subunit, inhibiting peptide bond formation
• lincosamides class of protein synthesis inhibitors that are similar to macrolides
• linked recognition a mechanism whereby a B cell and the helper T cell with which it interacts recognize the same antigen
• lipase extracellular enzyme that degrades triglycerides
• lipid bilayer biological membranes composed of two layers of phospholipid molecules with the nonpolar tails associating to form a hydrophobic barrier between the polar heads; also called unit membrane
• lipid macromolecule composed primarily of carbon and hydrogen; source of nutrients for organisms, a storage form for carbon and energy, a part of the structure of membranes, and may function as hormones, pharmaceuticals, fragrances, and pigments
• lipopolysaccharide (LPS) lipid molecules with attached sugars that are found as components of gram-negative outer membranes
• lipoprotein conjugated protein attached to a lipid
• listeriosis bacterial disease caused from the ingestion of the microbe Listeria monocytogenes
• lithotroph chemotroph that uses inorganic chemicals as its electron source; also known as chemoautotroph
• live attenuated vaccine vaccine with live pathogen that has been attenuated to become less virulent in order to produce an active but subclinical infection
• liver fluke a trematode worm that affects the bile duct of the liver, including Fasciola hepatica and F. gigantica
• local infection infection in one limited area
• log phase interval of growth when cells divide exponentially; also known as the exponential growth phase
• loiasis a disease caused by the parasitic Loa loa worm, which is transmitted by deerflies; adult worms live in the subcutaneous tissue and cause inflammation, swelling, and eye pain as they migrate through the skin and the conjunctiva of the eye
• lophotrichous having a single tuft of flagella located at one end of a bacterial cell
• low G+C gram-positive bacteria bacteria that have less than 50% of guanine and cytosine nucleotides in their DNA
• lumen space inside the cisternae of the endoplasmic reticulum in eukaryotic cells
• Lyme disease tickborne disease caused by the spirochete Borrelia burgdorferi
• lymph nodes bean-shaped organs situated throughout the body that contain areas called germinal centers, which are rich in B and T lymphocytes; also contain macrophages and dendritic cells for antigen presentation
• lymphadenitis inflammation of the lymph nodes
• lymphangitis inflammation of the lymphatic vessels
• lymphogranuloma venereum infection caused by Chlamydia trachomatis in tropical regions
• lyophilization rapid freezing, followed by placement under a vacuum, of a material so that water is lost by sublimation, thereby inhibiting microbial growth
• lysis destruction of the host cell
• lysogen bacterium carrying the prophage
• lysogenic conversion (phage conversion) alteration of host characteristics or phenotypes due to the presence of phage
• lysogenic cycle life cycle of some phages in which the genome of the infecting phage is integrated into the bacterial chromosome and replicated during bacterial reproduction until it excises and enters a lytic phase of the life cycle
• lysogeny process of integrating the phage into the host genome
• lysosome an organelle of the endomembrane system that contains digestive enzymes that break down engulfed material such as foodstuffs, infectious particles, or damaged cellular components
• lytic cycle infection process that leads to the lysis of host cells