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Biology Glossary - K


K
 Lysine
See amino acids

K antigens
 Capsular antigens – usually capsular polysaccharides. Examples include the capsular antigens of Streptococcus pneumoniae, colominic acid, and VI antigens. In Gram-negative bacteria, K antigens can mask O antigens; in some bacteria the K antigens can be removed by heating , but in others (e.g. Klebsiella spp) they are heat-stable. In Escherichia coli, several surface antigens originally designated K – e.g. K88, K99 – are actually (proteinaceous) fimbrial antigens, and it has been proposed that they be renamed F antigens (K88 = F4, K99 = F5); polysaccharide K antigens may occur together with fimbrial antigens in certain strains of E. coli.

K+-ATPase
 see ion transport.

K cells
 Killer cells: lymphoid cells which have cytotoxic/cytolytic activity against target cells; syn. NK CELLS.

K+ pump
see ion transport.

K-selection
The concept that in certain (K-selected) populations, life history is centered around producing relatively few offspring that have a good chance of survival.

K+ transport
see ion transport.

K virus
see polyomavirus.

K vitamins
see quinones.

K1 killer strain (of Saccharomyces cerevisiae)
see killer factor.

K1 RNA, K2 RNA
 see rnase p.

K88, K99
In Escherichia coli : fimbrial antigens of certain strains pathogenic in animals – see Etec, Fimbriae and K antigens.

Kabackosome
A type of vesicle formed by the hypotonic lysis of a sphaeroplast. A Kabackosome (which contains little or no cytoplasm) is composed of cytoplasmic membrane; the inner and outer faces of the membrane correspond to those in the original cell. (cf. ETP.)

KAF
 syn. factor i.

Kaffir pox
 see smallpox.

Kagami fever
see ehrlichia.

Kahn test
A standard test for syphilis.

kala-azar
see visceral leishmaniasis.

Kanagawa phenomenon
 The phenomenon in which those strains of Vibrio parahaemolyticus isolated from human patients exhibit clear (b) haemolysis when grown on WAGATSUMA AGAR containing human RBCs but not on that containing horse RBCs (a Kanagawa +ve reaction), while almost all strains isolated from other sources, including food suspected of causing V. parahaemolyticus food poisoning, do not (i.e. are Kanagawa −ve). (Discoloration (a-haemolysis) and clear haemolysis on both human and horse RBC-containing media are both regarded as Kanagawa −ve results.) The Kanagawa haemolysin is heatstable, extracellular, cytotoxic and cardiotoxic, and is haemolytic for human, dog and rat RBCs, weakly so for rabbit and sheep RBCs, and inactive against horse RBCs. In feeding experiments (in man), only Kanagawa +ve strains were capable of causing gastroenteritis, but the role of the haemolysin in pathogenesis is unknown; Kanagawa +ve strains appear to be better able to
multiply in the intestine than are Kanagawa −ve strains.

kanamycin
Any of several related aminoglycoside antibiotics (kanamycins A, B, C) produced by Streptomyces kanamyceticus; the drug used clinically is composed mainly of kanamycin A.

kanchanomycin (albofungin)
A complex polycyclic antibiotic, produced by Streptomyces sp, which has both antibacterial and antitumour activity. In the presence of divalent cations, kanchanomycin binds to DNA and inhibits DNA and RNA synthesis.

Kaposi’s sarcoma (KS)
A rare multifocal neoplastic disease which occurs in two forms: (i) slow and indolent (limited mainly to the skin), and (ii) rapid and fulminant (involving skin and gastrointestinal tract). The milder form occurs in certain ethnic groups (e.g. Ashkenazi Jews). The aggressive form occurs in children in tropical Africa and is also a common feature in HIV infected patients.  Kaposi’s sarcoma appears to be associated with human (gamma) herpesvirus 8 (HHV8) in conjunction with the immunosuppressive effects of HIV. Activation of latent HHV8 in vitro has been achieved by demethylation of the promoter of a transactivator region by means of the reagent tetradecanoylphorbol acetate (TPA), and studies on the level of methylation of the transactivator region in biopsies have suggested a relationship between methylation status and the development of HHV8- associated disease

Kaposi’s varicelliform eruption
 May refer either to eczema herpeticum or eczema vaccinatum


kappa chain
see light chain.

kappa particles
 see caedibacter.

Karatomorpha
 see proteromonadida.

K¨arber method
see end-point dilution assay.

Karelian fever
 see sindbis virus.

Karnal bunt (partial bunt; new bunt)
A wheat disease caused by Neovossia indica (formerly e.g. Tilletia indica); originally
a minor disease confined to NW India, it has recently spread through northern India and has become established in Afghanistan, Iraq, Pakistan, and Mexico, apparently transmitted on and in wheat seed. Usually only some of the grains in an ear are attacked; infected parts of the grain are initially grey but gradually turn black and emit a foul odour (trimethylamine).

karyogamy
The fusion of nuclei of two cells, as part of syngamy.
karyokinesis
Division of the nucleus during the cell cycle.
karyotype
(kar-ee-oh-type) [Gk. kara, the head + typos, stamp or print]
A method of organizing the chromosomes of a cell in relation to number, size, and type.
keratin
[Gk. karas, horn]
One of a group of tough, fibrous proteins formed by certain epidermal tissues and especially abundant in skin, claws, hair, feathers, and hooves.
keystone predator
A predatory species that helps maintain species richness in a community by reducing the density of populations of the best competitors so that populations of less competitive species are maintained.
keystone species
A species that is of exceptional importance in maintaining the species diversity of a community; when a keystone species is lost, the diversity of the community decreases and its structure is significantly altered.
kidney
In vertebrates, the organ that regulates the balance of water and solutes in the blood and the excretion of nitrogenous wastes in the form of urine.
kilocalorie (kcal)
A thousand calories; the amount of heat energy required to raise the temperature of 1 kg of water 1°C.
kin selection
A phenomenon of inclusive fitness, used to explain altruistic behavior between related individuals.
kinesis
(kih-nee-sis)
A change in activity rate in response to a stimulus.
kinetic energy
(kih-net-ik) [Gk. kinetikos, putting in motion]
The energy of motion, which is directly related to the speed of that motion. Moving matter does work by transferring some of its kinetic energy to other matter.
kinetochore
(kih-net-oh-kor) [Gk. kinetikos, putting in motion + choros, chorus]
A specialized region on the centromere that links each sister chromatid to the mitotic spindle.
kingdom
A taxonomic category, the second broadest after domain.
Koch's postulates
A set of four criteria for determining whether a specific pathogen is the cause of a disease.
Krebs cycle
A chemical cycle involving eight steps that completes the metabolic breakdown of glucose molecules to carbon dioxide; occurs within the mitochondrion; the second major stage in cellular respiration.


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