Karyotype
The distinctive chromosomal complement of a cell which may vary between
individuals of a single species, depending on the presence or absence
of particular sex chromosomes or on the incidence of translocations between
sections of different chromosomes.
Keto acid
Molecule formed from amino acid metabolism and containing carbonyl (-CO-)
and carboxyl (-COOH) groups.
Ketone
(= Ketone body) Product of fatty acid metabolism that accumulates
in blood during starvation and in untreated diabetes mellitus. e.g. acetoacetic
acid, acetone, or b-hydroxybutyric acid
Kinase
Enzyme that transfers a phosphate (usually from ATP) to another molecule.
Klenow
fragment (of DNA polymerase I) A DNA ploymerase enzyme, obtained by
chemical modification of E.coli DNA polymerase I, used primarily
in chain termination DNA sequencing.
Km
A parameter that describes the affinity of an enzyme for its substrate
and equals the substrate concentration that yields the half-maximal reaction
rate; also called the Michaelis constant. A similar parameter describes
the affinity of a transport protein for the transported molecule or the
affinity of a receptor for its ligand, since the kinetics of transport
and ligand binding are similar to those of enzymatic reactions.
Knockout
animal An animal whose endogenous gene for a particular protein
has been deleted or mutated to be non-functional.
Krebs cycle
Mitochondrial metabolic pathway that utilizes fragments derived from carbohydrate,
protein, and fat breakdown and produces carbon dioxide, hydrogen, and
small amounts of ATP. This cycle is called tricarboxylic acid (TCA) cycle,
citric acid cycle.
Kupffer
cells Phagocytic cells which line the liver sinusoids.