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
T cell
type of white blood cell that is produced in the bone marrow nut matures in the thymus gland. t lymphocytes coordinate the immune response and kill infected cells.
tissue fluid
fluid that surrounds the cells of the body. its composition is similar to that of blood plasma except that it lacks proteins. It supplies nutrients to the cells and removes waste products
tissue
a group of similar cells organised into a structural unit that serves a particular function
tidal volume
the volume of air breathed in and out during a single breath when at rest
thylakoid
series of flattened membranous sacs in a chloroplast that contain chlorophyll and the associated molecules needed for the LDR
thrombosis
formation of a blood clot within a blood vessel that may lead to a blockage
threshold level/value
the minimum intensity that a stimulus much reach in order to trigger an action potential in a neurone
the tertiary structure (protein)
the folding of a whole polypeptide chain in a precise way. as determined by the amino acids of which it is comprised
tension
tough, flexible, but inelastic, connective tissue that joins muscle to bone
systole
the stage in the cardiac cycle in which the heart muscle contracts. Occurs in two stages: atrial systole and ventricular systole
synapse
a junction between neurones in which they do not touch but have a narrow gap across which a neurotransmitter may pass
symplastic pathway
route through the cytoplasm and plasmodesmata of plant cells by which water and dissolved substances are transported
supernatant liquid
the liquid portion of a mixture left at the top of the tube when suspended particles have been suspended out at the bottom during centrifugation
substrate-level phosphorylation
the formation of ATP by the direct transfer of a phosphate group from a reactive intermediate to ADP
substrate
a substance that is acted or used by another substance or process. In microbiology, the nutrient medium used to grow microorganisms
stroma
matrix of a chloroplast where the LIDR occurs
stroke volume
the volume of blood pumped at each ventricular contraction of the heart
stoma (plural stomata)
a pore, mostly found in the lower epidermis of a leaf, through which gases diffuse in and out of the leaf
stimulus
a detectable alteration in the internal or external environment of an organism that produces some change in that organism
stem cells
undifferentiated dividing cells that occur in embryos and in adult animal tissues that require constant replacement
stabilising selection
selection that tends to eliminate the phenotype range within a population. It arises when environmental conditions are constant
species diversity
a group of similar organisms that can breed together to produce fertile offspring
speciation
the evolution of two or more species from existing species
Sodium-potassium pump
protein channels across a cell-surface membrane that use ATP to move sodium ions out of the cell in exchange for potassium ions that move in
Smooth Muscle
a.k.a. involuntary or unstriated, smooth muscle is found in the alimentary canal and the walls of blood vessels. Its contraction is not under conscious control
skeletal muscle
the muscle that makes up the bulk of the body and which works under conscious control. A.KA.. voluntary muscle
Sinoatrial node (SAN)
an area of the heart muscle in the right atrium that controls and coordinates the contraction of the heart. (PACEMAKER)
sickle-cell anaemia
inherited blood disorder in with abnormal haemoglobin leads to red blood cells become sickle-shaped and less able to carry oxygen
serum
clear liquid that is left after blood has clotted and the clot has been removed (blood plasma without clotting factors)
