Bio definitions Flashcards
Xylem vessels
dead, hollow elongated tubes, with lignified side walls and no end walls, that transport water in most plants
Xerophyte
a plant adapted to living in dry conditions
Water potential
the pressure created by water molecules. It is the molecule of the extent to which a solution gives out water. The greater the number of water molecules present, (less negative) than the water potential. Pure water has a water potential of zero.
Voltage-gated channel
protein channel across a cell-surface membrane that opens and closes according to changes in the electrical potential across the membrane
Vector
a carrier. e.g. a plasmid (dna into a cell) or an organism (carries a parasite to its host)
Vasodilation
widening of the internal diameter of the blood vessels.
Vasoconstriction
narrowing of the internal diameter of the blood vessels
Vaccination
the introduction of a vaccine containing appropriate disease antigens into the body, by injection or mouth, in order to induce artificial immunity.
unsaturated fatty acid
a fatty acid in which there are one or more double bonds in the carbon atoms.
ultrafiltration
filtration assisted by blood pressure, e.g. in the formation of tissue fluid
turgid
a plant cell that contains the maximum volume of water it can. Additionally, entry of water is prevented by the cell wall stopping further expansion of the cell.
tumour suppressor gene
a gene that maintains normal rates of cell division and so prevents the development of tumours
tumour
swelling in an organism that is made up of cells that continue to divide in an abnormal way
trophic level
the position of an organism in a food chain
triglyceride
an individual lipid molecule made up of a glycerol molecule and three fatty acids
transpiration
evaporation of water from a plant
transduction
the process by which one form of energy is converted into another. In microbiology, the natural process by which genetic material is transferred between one host cell and another by a virus
transducer cells
cells that convert a non-electrical signal, such as a light or sound, into an electrical (nervous) signal and vice versa
transcription
formation of mRNA molecules from the DNA that makes up a particular gene. It is the first stage of protein synthesis