Bio definitions

Question 1

Xylem vessels

Answer 1

dead, hollow elongated tubes, with lignified side walls and no end walls, that transport water in most plants

Question 2

Xerophyte

Answer 2

a plant adapted to living in dry conditions

Question 3

Water potential

Answer 3

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.

Question 4

Voltage-gated channel

Answer 4

protein channel across a cell-surface membrane that opens and closes according to changes in the electrical potential across the membrane

Question 5

Vector

Answer 5

a carrier. e.g. a plasmid (dna into a cell) or an organism (carries a parasite to its host)

Question 6

Vasodilation

Answer 6

widening of the internal diameter of the blood vessels.

Question 7

Vasoconstriction

Answer 7

narrowing of the internal diameter of the blood vessels

Question 8

Vaccination

Answer 8

the introduction of a vaccine containing appropriate disease antigens into the body, by injection or mouth, in order to induce artificial immunity.

Question 9

unsaturated fatty acid

Answer 9

a fatty acid in which there are one or more double bonds in the carbon atoms.

Question 10

ultrafiltration

Answer 10

filtration assisted by blood pressure, e.g. in the formation of tissue fluid

Question 11

turgid

Answer 11

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.

Question 12

tumour suppressor gene

Answer 12

a gene that maintains normal rates of cell division and so prevents the development of tumours

Question 13

tumour

Answer 13

swelling in an organism that is made up of cells that continue to divide in an abnormal way

Question 14

trophic level

Answer 14

the position of an organism in a food chain

Question 15

triglyceride

Answer 15

an individual lipid molecule made up of a glycerol molecule and three fatty acids

Question 16

transpiration

Answer 16

evaporation of water from a plant

Question 17

transduction

Answer 17

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

Question 18

transducer cells

Answer 18

cells that convert a non-electrical signal, such as a light or sound, into an electrical (nervous) signal and vice versa

Question 19

transcription

Answer 19

formation of mRNA molecules from the DNA that makes up a particular gene. It is the first stage of protein synthesis

Question 20

T cell

Answer 20

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.

Question 21

tissue fluid

Answer 21

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

Question 22

tissue

Answer 22

a group of similar cells organised into a structural unit that serves a particular function

Question 23

tidal volume

Answer 23

the volume of air breathed in and out during a single breath when at rest

Question 24

thylakoid

Answer 24

series of flattened membranous sacs in a chloroplast that contain chlorophyll and the associated molecules needed for the LDR

Question 25

thrombosis

Answer 25

formation of a blood clot within a blood vessel that may lead to a blockage

Question 26

threshold level/value

Answer 26

the minimum intensity that a stimulus much reach in order to trigger an action potential in a neurone

Question 27

the tertiary structure (protein)

Answer 27

the folding of a whole polypeptide chain in a precise way. as determined by the amino acids of which it is comprised

Question 28

tension

Answer 28

tough, flexible, but inelastic, connective tissue that joins muscle to bone

Question 29

systole

Answer 29

the stage in the cardiac cycle in which the heart muscle contracts. Occurs in two stages: atrial systole and ventricular systole

Question 30

synapse

Answer 30

a junction between neurones in which they do not touch but have a narrow gap across which a neurotransmitter may pass

Question 31

symplastic pathway

Answer 31

route through the cytoplasm and plasmodesmata of plant cells by which water and dissolved substances are transported

Question 32

supernatant liquid

Answer 32

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

Question 33

substrate-level phosphorylation

Answer 33

the formation of ATP by the direct transfer of a phosphate group from a reactive intermediate to ADP

Question 34

substrate

Answer 34

a substance that is acted or used by another substance or process. In microbiology, the nutrient medium used to grow microorganisms

Question 35

stroma

Answer 35

matrix of a chloroplast where the LIDR occurs

Question 36

stroke volume

Answer 36

the volume of blood pumped at each ventricular contraction of the heart

Question 37

stoma (plural stomata)

Answer 37

a pore, mostly found in the lower epidermis of a leaf, through which gases diffuse in and out of the leaf

Question 38

stimulus

Answer 38

a detectable alteration in the internal or external environment of an organism that produces some change in that organism

Question 39

stem cells

Answer 39

undifferentiated dividing cells that occur in embryos and in adult animal tissues that require constant replacement

Question 40

stabilising selection

Answer 40

selection that tends to eliminate the phenotype range within a population. It arises when environmental conditions are constant

Question 41

species diversity

Answer 41

a group of similar organisms that can breed together to produce fertile offspring

Question 42

speciation

Answer 42

the evolution of two or more species from existing species

Question 43

Sodium-potassium pump

Answer 43

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

Question 44

Smooth Muscle

Answer 44

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

Question 45

skeletal muscle

Answer 45

the muscle that makes up the bulk of the body and which works under conscious control. A.KA.. voluntary muscle

Question 46

Sinoatrial node (SAN)

Answer 46

an area of the heart muscle in the right atrium that controls and coordinates the contraction of the heart. (PACEMAKER)

Question 47

sickle-cell anaemia

Answer 47

inherited blood disorder in with abnormal haemoglobin leads to red blood cells become sickle-shaped and less able to carry oxygen

Question 48

serum

Answer 48

clear liquid that is left after blood has clotted and the clot has been removed (blood plasma without clotting factors)