AS Biology Definition

8/6/2019 AS Biology Definition

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Word DefinitionAcid A substance which forms H+ ions and acts as a proton

donor.Acrosome Membrane-bound storage sac of enzymes in the head of a

sperm.Acrosome reaction Release of enzymes from the acrosome when the head of

the sperm touches the surface of the ovum.Activation energy The energy needed to make or brake bonds at the

beginning of a chemical reaction.Active site Area of enzyme with specific shape which fits shape of

substrate molecules.Active transport Form of cellular transport in which energy is used to move

substances against a concentration gradient.Adenine A purine base in DNA and RNAAdenosine diphosphate

(ADP)

Molecule produced when a phosphate group is removed

from ATPAdenosine triphosphate(ATP)

Molecule that releases energy when the terminal phosphate bond is broken, to from adenosine triphosphate

Adhesion Attraction of different moleculesAgouti Coat coloring, e.g. in catsAlbinism Genetic condition in which the natural melanin pigment of

the skin, eyes and hair does not formAllele Different forms of a gene.Allopatric speciation Speciation that results when populations are physically

separated in some wayAltruistic An action that benefits others without any direct benefit to

the individualAlveolus (plural alveoli) Minute air sacs in the lungs where gas exchange takes

placeAmino Acid Sub-unit of proteins.Amniocentesis Prenatal test that involves taking a sample of amniotic

fluid at around 16 weeks of a pregnancy and culturing thefetal cells to look for genetic abnormalities.

Amphoteric Can act as both an acid and a baseAmylopectin Polymer of glucose with many branched chainsAmyloplast Plant organelles involved in amylopectin (a form of

starch)Anabolic Reaction Reaction that builds new chemical from more than one

reactant.Anaerobic respiration The release of energy from glucose without the use of

oxygenAnaphase Fourth stage of mitosis where chromatids are pulled

towards the poles of the cellAnatomical adaptation Adaptations of the anatomy of an animal or plant to

conditionsAneurysm A bulge in the wall of an artery as a result of pressure of

blood building up behind a narrowed area. This leaves the

wall weakened and vulnerable to splitting openAngina Chest pain or discomfort that occurs when the heart isnt


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getting enough oxygen because of reduced blood flow tothe cardiac muscle. Usually the result of atherosclerosisand is a symptom of coronary heart disease

Angiogenesis Growth of new blood vesselsAnther Male sex organ in plantsAntibodies Protein produced on response to the presence of a specific

antigen on the surface of a foreign cellAnticoagulant Drug that prevents the blood from clottingAntihypertensive Drug that lowers blood pressureAntisense Strand The strand of DNA which acts as a template for the

formation of mRNA.Antitoxin An antibody that can neutralize a toxin made by a specific

pathogenAorta Main artery leaving the left side of the heart carrying

oxygenated blood to the body

Apoplast Cell wallsApoplast pathway Pathway through cell walls travelled by water moleculesfrom soil to xylem as a part of transpiration stream

Apoptosis Programmed cell death, also known as cell suicideArtifact A feature present as a result of human actions in preparing

material rather than a natural feature of the tissue or cellArteriole Vessel that links an artery and capillaryArtery Vessel carrying blood away from the heartAsexual reproduction The production of genetically identical offspring from a

single parent cell or organismAspirin Painkiller or anticoagulantAssimilation The taking-in of new material by cells after cell divisionAtheroma Fatty deposits initially laid down on damaged arterial

liningAtherosclerosis Hardening of the arteries the build-up of hardened fatty

deposits on the arterial liningATPase Enzyme that catalyses the breakdown of ATP to ADP

with the release of useful energy for the cellAtrial systole The contraction of the atria forcing blood into the

ventriclesAtrioventricular valve Bicuspid and tricuspid valves

Autoradiography A technique using photographic film to show upradioactively labeled substances in plants and other organisms

Autosome Chromosome that carries information about somatic(body) cells and their biochemistry (not a sexchromosome).

Bacterial conjugation Sexual reproduction in bacteriaBalancing selection A form of natural selection that maintains a

disadvantageous allele in a population because of the benefit to the heterozygote.

Barr body Mass of inactivated X chromosome in cells of female

mammalsBasal metabolic rate The energy needed for the basic metabolic reactions of the


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(BMR) body to take placeBase Forms OH ions and acts as a proton acceptor Behavioral adaptation An adaptation of the behavior of an animal which gives it

a selective advantageBehavioral isolation Reproductive isolation resulting from changes in the

courtship ritual, display or mating patternBeta blocker Drug that blocks the response of the heart to adrenaline,

slowing the heart rate and lowering blood pressureBias Influence in a particular directionBicuspid valve Valve found between the left atrium and the left ventricle

of the heart. One of the atrioventricular valvesBilayer Double layer Biodiversity The number and variety of different organisms found in a

particular areaBiodiversity hotspot Area which is particularly rich in different species

Bioindicator Species that is particularly sensitive to change and so can be used to indicate problems in an area which might leadto loss of biodiversity

Boiplastic Plastic (polymer) made from monomers which come froma sustainable biological source

Blastocyst Early embryo consisting of a ball of cellsBody mass index (BMI) A formula for comparing your weight to your height used

to indicate obesity levelsBreathing Movement of air in and out of the respiratory systemBronchi Tubes leading from the trachea into the left and right

lungs

Bronchiole Small tube leading from the bronchi and spreadthroughout the lungs

Budding Form of asexual reproduction involving an outgrowthfrom the parent plant which develops into a smaller,genetically identical individual

Buffer A substance that tends to prevent change in pH when anaid or base is added to a solution

Calorimeter A process which measures the amount of energycontained in a substance, e.g. food

Capillary Narrow blood vessels with walls one cell thick which penetrate between the cells of the body and link arteriesand veins. Materials diffuse into and out of the bloodthrough the capillary walls

Captive breeding program

Breeding individuals from an endangered species in zoosand parks to save species from extinction

Capture/recapturetechnique

Method of estimating the population of a particular species in an area which involves capturing individuals,marking them and releasing them and then capturing someof the again

Carbaminohaemoglobin Haemoglobin combined with carbon dioxideCarbohydrates Molecules made of carbon, hydrogen and oxygen that

supply the body with energy. Sub-units are known asmonosaccharides


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Carbonic anhydrase The enzyme that controls the rate of the reaction betweencarbon dioxide and water to from carbonic acid

Carbon-neutral No net release of carbon compounds into the atmosphereCardiac cycle The time taken for a single heart beat as the heart goes

through diastole and systoleCardiac muscle The muscle which makes up the heartCardiovascular center Center in the brain which responds to the carbon dioxide

levels in the blood and controls the heart rate.Cardiovascular disease(CVD)

Diseases of the heart and blood vessels, particularly heartattacks and strokes

Cardiovascular system The heart and blood vesselsCarotid arteries Large arteries which branch off the aorta to supply

oxygenated blood to the headCarrier An individual that has one allele (heterozygous) for a

genetic disease so does not suffer from it but can pass the

allele to its offspringCarrier protein A protein that carries a specific molecule or type of molecule through a membrane

Casparian strip Waterproof layer of cells in a root containing suberinCatabolic reactions Reactions that breakdown a chemical into more than one

productCatalyst A substance that speeds up a chemical reaction.Cause A factor that directly causes somethingCell cycle Sequence of events making up cell divisionCell determination Predestination of embryonic cells to become particular

tissues

Cell sap Contents of vacuole in plant cellsCell surface membrane The membrane (a phospholipid bilayer with protein

floating and embedded in the structure) that surrounds thecytoplasm and controls the movement of substances intoand out of the cell.

Cell theory Theory that cells are the basic unit of living organismsCellulose Complex carbohydrate which is a major component of

plant cell wallsCell wall Tough outer layer around plant cells made up mainly of

celluloseCentrioles Structure in an animal cell that are involved in spindle

formation during cell divisionCentromere The region where the chromatids are joined together in

pairs before separating during cell divisionChannel protein Protein in membranes that allows passage of substances

through the membraneChiasma (plural chiasmata) points where chromatid break during

crossing over Chlorophyll Green pigment found in plants which traps energy from

sunlight. Needed for photosynthesisChloroplast Organelle in some plants cells which contains chlorophyll,

site of photosynthesisChorionic villus Prenatal test for genetic disorders which involves


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sampling sampling fetal tissue from the placenta at 10-12 weeksChromatid One of the two strands formed when a chromosome

replicates in cell divisionChromatin DNA bound to protein when a cell is not actively dividingChromatography Technique for separating the components of a mixture

based on movement of different-sized particles in asolvent

Chromosomal Mutation Mutation involving changes in the positions of geneswithin the chromosome.

Cilia Hair-like projections from the cells which move backwards and forwards. They line the respiratory tractand move mucus up and away from the lungs

Circulation Movement of the blood around the body in thecardiovascular system

Cleavage Special form of mitosis which involves rapid cell divisionwithout interphase pauses for assimilation and cellexpansion

Clone Genetically identical individuals that result from asexualreproduction

Codon Three base pairs of DNA or RNA coding for a particular amino acid.

Cohesion Technology of water molecules to stick together Collenchyma Supporting tissue in plantsColloid A mixture in which very small particles of one substance

are distributed evenly throughout another substance. Thesolute particle of a colloid are larger than particles of a

solventCommunity All of the populations of living organisms which live in

habitat at any one timeComplementary BasePairing

Purine and pyrimidine bases that always pair up in theformation of DNA or RNA.

Complementary DNA DNA made by reversing the normal transcription process.It can act as an artificial gene.

Complementary Strand The mRNA strand formed alongside the original DNAstrand during translation of the genetic code into proteins.

Composite material Material made up of a combination of two or moresubstances which all contribute to the properties of thefinal composite

Concentration gradient The difference between an area where a solute is at highconcentration and an area where the same solute is at arelatively low concentration

Conception The fusing of the sperm and the ovumCondensation reaction Reaction in which two substances are joined together and

a molecule of water is producedConjugated protein Protein molecules joined to other substances, eg iron,

carbohydrateConservation Looking after a living and changing environment

Constrict Get narrower Continuous growth Growth which occurs continuously, although at different


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rates, throughout life at least until maturity is reachedContinuous variation A feature that shows many small variationsContractile vacuole Vacuole found in simple animals that forms and empties

to control water content of the cytoplasmCorrelation A factor that appears to be linked to a change or event, eg

both increase or decrease at the same timeCristae Infoldings of the mitochondrial inner membrane which

provides a large surface area for enzyme actionCritically endangered Facing an extremely high risk of extinction in the wildCrossing over Process by which chromatids break and rejoin,

introducing variety during meiosisCross-linking Intermolecular bonds which hold cellulose chains together Cross-species cloning Cloning animals using a closely related species as a

surrogate mother and provider of the empty eggCutin A waxy, waterproof polymer which covers the surface of

plantsCyanide Poison that acts by preventing the release of energy fromATP

Cyclin Small protein involved in control of the cell cycleCyclin/CDK complex Cyclin-dependent kinases (CDKs) bound to the protein

cyclin in a complex which controls the cell cycle through phosphorylation of protein

Cyclin-dependentkinases (CDKs)

Enzymes involved in the control of the cell cycle

Cystic Fibrosis (CF) Genetic disease in which a membrane transport protein isnot formed properly, leading to problems with chloride

ion transport and damage to tissues as a result of verythick mucus.

Cystic fibrosistransmembraneregulatory channel

protein (CFTR channel protein)

The membrane transport protein which is affected incystic fibrosis

Cytokinesis Division of the cytoplasm to form two daughter cellsduring cell division

Cytoplasm The jelly-like liquid inside a cell containing organellesCytosine A pyrimidine base in DNA and RNACytoskeleton 3D web-like structure that fills the cytoplasm, made up of

microfilaments and microtubules.Denature When the tertiary and quaternary structure of the protein is

destroyed.Deoxygenated Containing reduced levels of oxygen, as in blood leaving

the body cellsDNA (deoxyribonucleicacid)

Nucleic acid that forms genetic material of the cell.

Diastole When the heart relaxes and fills with bloodDiastolic blood pressure The blood pressure reading taken when the heart is

relaxedDietary reference values Range of appropriate food intakes for different groups of


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the populationDifferentiate The process by which cells become specialized for a

particular function and lose the ability to from differenttypes of cells (lose pluripotency)

Diffusion Free movement of particles in a liquid or a gas down aconcentration gradient from an area of relatively highconcentration to an area of relatively low concentration

Digitalin A compound found in foxgloves which at low dosesmakes the heart beat more powerfully. It is toxic at higher doses

Diglyceride A fat or oil containing only two fatty acidsDilate Get wider Dipeptide Molecule formed when two amino acids are joined by a

peptide link Diploid Having two sets of chromosomes in cell (2n)

Dipole Very small, equal and opposite electric charges within amoleculeDirectional selection A change from one phenotype to another which is more

advantageous under the circumstancesDisaccharide Double sugar unit, eg sucroseDiscontinuous growth Growth which takes place in a serious of stepsDiscontinuous variation Variation shown by features which are either present or

notDisplayed formula Chemical formula showing the basic arrangement of

atoms within a moleculeDiuretic Drug that increases the volume of urine produced

Diversifying selection A form of natural selection which results in increasedgenetic diversity of a population

DNA Helicase Enzyme that unzips the two strands of DNA at the start of replication.

DNA ligase One of the enzymes that joins nucleotides together fromDNA strands.

DNA polymerase One of the enzymes that joins nucleotides together fromDNA strands.

Dominant Allele which is expressed phenotype whether theindividual is homozygous or heterozygous.

Dopamine Monoamine neurotransmitter Double-bind trial Drug trial where neither the doctor nor the patient knows

whether they are getting the active new treatment or notDouble circulation Double circulatory system where deoxygenated blood is

pumped from heart to respiratory organs and oxygenated.It is then returned to the heart to be pumped into another separate system to be carried around the body to thetissues before deoxygenated blood is returned to the heart

Double fertilization In plants where one male gamete fuses with two polar bodies and the other fuses with the female gamete (egg)nucleus to from a zygote

Double Helix Molecular structure made famous by DNA that involvestwo strands twisted together like a spiral staircase.


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Dry mass The mass of the body of an organism with all the water removed

Ecdysone Insect hormone that controls the molting processEcological isolation Breeding isolation when two populations inhibit the same

region but develop preferences for different parts of thehabitat

Ecological niche The role of an organism within an ecological communityEcological species Definition of species based on the ecological niche

occupied by the organismsEcology The study of the relationships between living organisms

and their environmentEcosystem Environment including all the living organisms

interacting, the cycling of nutrients and the physical andchemical environment in which organisms are living

Electrocardiogram(ECG)

A recording of the electrical activity of the heart, oftenused to help diagnose heart problems

Electron micrograph(EM)

Photograph taken using an electron microscope

Electron microscope Microscope that uses a beam of electrons to form animage, which allows very high levels of magnification

Electrophoresis A method of separating amino acids by their movementthrough an inert gel under the influence of an electric field

Electrostatic attraction Attraction between opposite charges (positive andnegative)

Embryonic stem cell Cells from the early embryo which are pluripotent or totipotent, can form most or all of the cell types of an

organismEmbryo sac Contains the gametophyte generation in the ovary of the

flowering plantsEmbryo splitting Process of splitting early embryos while the cells are

totipotent to produce a number of identical clones inanimal husbandry

Emulsion Tiny droplets of one liquid suspended in another liquidEndangered Facing a very high risk of extinction in the wildEndemic A species which is a unique to an areaEndemism Species which only occur in a very specific small area

such as an island, they are unique to the areaEndocytosis Taking particles into the cell; on a large scale this is

phagocytosis, on a small scale it is pinocytosisEndoplasmic reticulum(ER)

A 3D network of membrane-bound cavities spreadingthrough the cytoplasm. Plays a major role in transportwithin the cell

Endosperm nucleus Triploid nucleus formed when male nucleus fuses withtwo polar bodies in ovule of a plant

Endothelium Layer of epithelial cells which lines the chambers of theheart, the blood vessels and the lymph vessels

Enzyme Biological catalyst

Epidermis Outer layer of cells in a plant leaf, outer layer of the skinEpiglottis Tissue which closes over the glottis in a reflex action


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when you swallowEpistasis When one gene in a polygenic trait alters or affects the

expression of another geneEpithelial tissues Tissues which line the surfaces inside and outside the

bodyErythrocyte Red blood cellEssential amino acid Amino acid that cannot be synthesized in the body and so

must be taken in as part of the dietEster bond Bond formed in the condensation reaction between the

carboxyl group of a fatty acid and one of the hydroxylgroups of glycerol, with the elimination of a molecule of water

Esterification Condensation reaction by which fatty acids are combinedwith glycerol to form lipids

Eubacteria One of the most common types of bacteria

Eukaryote Cell or organism where the nucleus is surrounded by anuclear membraneEvaluate Judge the value of a study, procedure or technique in

terms of accuracy, validity, reliability, precision,reproducibility, etc.

Evolution The process by which species of living organismsundergo permanent change as a result of a naturalselection n response to a change in their environment

Exhalation Moving air out of the respiratory systemExocytosis Moving substances out of a cell by emptying a membrane-

bound vesicle

Expressed To show, as in effect of an allele on the phenotype.External fertilization Fertilization that takes place outside the bodyExternal stimulus Signal or change from outside the body or cellExtinction The permanent loss of all members of a speciesExtracellular enzymes An enzyme that works outside the cells, such as digestive

enzymes.F1 (first filial generation) The first generation of offspring in a genetic cross.F2 (second filialgeneration)

The offspring that result from a cross of the F1 generation.

Facilitated diffusion Diffusion that takes place through specificchannels/carriers but which does not use up energy

Fat A lipid that is solid at normal room temperatureFatty acid Long-chain organic acid that makes up part of the

structure of lipidsFertilization Joining of two gametes to form a new individual (zygote)Fertilization membrane Thick membrane formed around the outside of an ovum

once it has been fertilized by a spermFiber Molecules that cannot be digested in the gut and add bulk

to the dietFibrin Fibrous protein involved in clot formationFibrinogen Precursor of fibrin

Fibrous protein Protein that forms long, fibrous structures and has little or no tertiary structure


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Ficks law The relationship between surface area, concentrationgradient and thickness of the exchange membrane whichdetermines the rate of diffusion

Fission In biology, the simple method of asexual reproductionwhich involves an organism splitting in two. Seen in

bacteria and protoctistsFixing Preserving a biological specimen to be viewed under a

microscopeFlaccid FloppyFluid mosaic model Currently accepted model of the structure of the cell

membraneFollicle In reproduction, the region where the ovum matures in the

ovaryFood staple Main energy supplying foods in the dietFounder effect Process by which any unusual alleles become relatively

common in a population if only a small number of individuals set up a population and one of the founder members has the unusual allele.

Fragmentation Reproduction of an entire individual from a bodyfragment

Frequency distribution Representation of the frequency at which a particular characteristic is found in a population

Gamete Sexual cell with half the chromosome number of anordinary cell

Gametogenesis Formation of the gametesGametophyte Haploid, sexual reproduction of plants

Gene Unit of inheritanceGene flow The movement of genes by the interbreeding of

individuals in different populationsGene linkage Genes that are inherited together in a linked unit of a

chromosomeGene pool All the different versions of genes (alleles) found in a

populationGene probe Technique for indentifying active genes in a cellGeneral formula Formula representing any member of a given chemical

family showing the ratio of the different types of atomsGenerative nucleus Nucleus in the pollen tube containing the chromosomes

which fuses with the female nucleus in the ovuleGene therapy Treatment that involves replacing faulty genes with

healthy onesGenetic diversity Variety of genes and alleles within a populationGenetic engineering Artificially changing the genetic material of an organism.Genetic modification Copying healthy genes and inserting them into the DNA

of other organismsGenetic pedigreediagram

A family tree showing the sex of the individuals and if they are affected by a genetic condition or not

Genetic screening Testing populations for a genetic disease

Genotype The genetic make-up of an organismGenus Group of similar species


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Geographical isolation A physical barrier, eg a river or mountain range, thatseparates individuals and prevents breeding

Germinate The growth of the pollen grain on the stigma of a plant.The growth of a seed into a young plant

Globular protein Protein with tertiary and sometimes quaternary levels of 3D organization, holding them into globular shapes

Glottis ThroatGlycerol Propane-1,2,3-triol, a compound that makes up part of the

structure of lipidsGlycogen Storage carbohydrate in animalsGlycoprotein Protein with a carbohydrate prosthetic groupGlycosidic bond Bond joining two monosaccharide units together Golgi body Stacks of parallel, flattened membrane pickets loosely

linked to the RER and involved in the secretion of materials from the cell

Gonad Organ that produces sex cells, such as testis or ovary inhumansGuanine A purine base in DNA and RNAGuttation When water is forces out of the leaves in drops as a result

of root pressure when transpiration rates are lowHabitat Place where an organism livesHemoglobin Red pigment which carries oxygen in the bloodHaploid Cell containing a single set of chromosomes (half the full

chromosome number (n))Heartbeat The sound made by blood hitting the heart valves as it

flows through the heart

Heterozygote Individual with different alleles for the same geneHeterozygote advantage(Hybrid vigour)

When the heterozygous state for a particular gene givesadvantages to the individual

Heterozygous Having different alleles of the same geneHexose Monosaccharide containing six carbon atomsHistone Positively charges protein molecule around which DNA

molecules coilHomologouschromosome

One of a matching pair of chromosomes

Homologous pair Matching pairs of chromosomes

Homozygote An individual with both alleles for a gene the sameHomozygous Having both alleles of a gene the sameHormone Chemical messenger made in an endocrine gland, secreted

into the body to the effector glandHuman Genome Project Massive international research program that mapped the

entire human genomeHuntigtons disease Genetic disease caused by a dominant allele that develops

in middle age and is fatalHydrogen bond The weak electrostatic attraction between oppositely

charges dipoles of different moleculesHydrolysis Splitting a compound by reacting with water

Hydrophilic Water-lovingHydrophobic Water-hating


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Hypertension High blood pressureHypertonic A solution with a higher solute concentration (lower

solvent concentration) than the cell contentsHypotension Low blood pressureHypotonic A solution with a lower solute concentration (higher

solvent concentration) than the cell contentsIndependent assortment The random distribution of chromosomes from parents

into offspringIndicator species Species which can be used to monitor pollination levels,

food levels etcInduced fit hypothesis Modified version of the lock-and-key hypothesis of

enzymes action that proposes a flexible shape for theactive site which is modified once the substrate moleculeis bound to form an active complex.

Industrial melanism Changes in the coloration of a population as a response toenvironmental changes from industrial activity

Inferior vena cava Major vein carrying deoxygenated blood from the lower part of the body back to the heart

Inflammatory response The response of the body to damaged tissue whichinvolves swelling and increased blood flow bringing white

blood cells to the areaInhalation Moving air into the respiratory systemInsulin Hormone produced by the pancreas that controls the

concentration of glucose in the bloodInternal fertilization Fertilization which takes place inside the bodyInternal stimulus Signal or change from inside the body or cell

Interphase Period of non-division in the cell cycleIntracellular Within a cellIntracellular enzymes Enzymes hat work inside the cell.Intrinsic rhythmicity The basic rhythm of the heart beat which is present in the

individual cellsIonic bond A chemical bond formed between two ions with opposite

chargesIonic substance A substance made up of oppositely charged ions held

together by ionic bondsIsomer One of two or more compounds made up of the same

atoms arranged differentlyIsotonic (Isosmotic) A solution with the same osmotic concentration as the cell

contentsJuvenile hormone Insect hormone that controls the maturity of the instar

produced after each moultKaryotype Image showing the chromosomes arranged into

homologous pairs.Keystone species A species which has a major effect on its environment. A

large number of other species depend on a keystonespecies for their survival

Lac operation Cluster of genes involved with the production of lactose in

bacterial cellsLarynx Voice box


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Law of independentassortment: Mendelssecond law

Law of genetics, originally proposed by Gregor Mendel,which states that different traits are inheritedindependently of each other.

Law of segregation:Mendels first law

Law of genetics, originally proposed by Gregor Mendel,which states that one allele for each trait is inherited fromeach parent and each pair of alleles is segregated(separated) when the gametes are formed.

Left atrium The small upper chamber of the heart on the left that fillswith oxygenated blood from the lungs

Left ventricle The larger lower chamber of the heart on the left that pumps oxygenated blood out of the heart into the aorta totravel around the body

Leucocyte White blood cellLeucoplast A range of plant organellesLifestyle The way someone lives their lifeLight microscope A microscope which relies on light to form an imageLignin Organic compound that binds to cellulose fibers and

makes them hard and strongLipid Molecule that contains a lot of stored chemical energy.

Supplies body with energy and also used as an energystore. Made up of fatty acids and glycerol

Lipoprotein A protein with a lipid group attachedLock-and-key hypothesis Model of enzymes action based on the idea of an active

site which fits specific reactants.Locus Position of a gene on a chromosomeLongitudinal study Studies which follow the same group of individuals over a

long period of timeLumen The central space inside a blood vessel or other tube, eg

the lumen of the gutLung surfactant Phospholipid that coats the surface of the alveoli and

makes it easier to move air in and outLymphocyte Type of white blood cellLysosome Organelle containing lysozymesMacromolecule Very large moleculeMacronutrient Nutrient needed in large amounts by the body, ef fat,

protein and carbohydrateMalignant A tumor which invades surrounding tissues and splits to

form secondary tumorsMalnutrition A condition linked to an inadequate diet, eg either too

much or too little food or the wrong type of foodMarsupial Mammal that gives birth to very immature young which

then complete their development in a pouchMass transport system A transport system which involves the flow of a fluid in a

system with a mechanism for moving it aroundMating Process by which male gametes are released directly into

the body of the femaleMatrix Surrounding substance

Mechanical isolation Reproductive isolation caused by anatomical changes inan animal or plant as a result of mutation which


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reproduction impossibleMegagamete The female gamete in a plantMegagametogenesis Process by which the female gametes are formed in plantsMegakaryocyte Large bone marrow cell which is the origin of platelets in

the bloodMegaspore Precursor of female gamete in plantsMeiosis Cell division which results in the production of four

daughter cells each with half of the chromosome number of the original

Melanocyte Pigment-forming cellMelanoma Cancer of the cells that produce the pigment melaninMesosome Fold of the cell surface membrane that can form a vesicleMessenger RNA(mRNA)

RNA that carries information from the DNA in thenucleus out into the cytoplasm to be translated into

proteins on the ribosomes.

Metabolic chain or pathway Sequence of metabolic reactions.

Metabolism Combination of anabolic and catabolic reactions that take place in body cells.

Metadata analysis Looking at a large number of studies and putting the datatogether

Metaphase Third stage of mitosis where chromatids line up across theequator of the cell

Metaphase plate Central region of spindle formed in mitosisMetastasis Splitting of a malignant tumor to form secondary growthMetaxylem The xylem which develops second, after the protoxylemMicelle Structure formed by a cluster of molecules with both

hydrophilic and hydrophobic ends when placed in water Microfibril A group of 10- 100000 cellulose moleculesMicrofilament Protein fibers that make up part of the cytoskeletonMicrogametogenesis Process by which the male gametes are formed in plantsMicrohabitat Small area of a larger habitatMicronutrient Nutrient needed in tiny amounts by body, eg vitamins and

some mineralsMicrospore Precursor of male gamete in plantsMicrotubule Tiny protein tubes that make up part of the cytoskeleton

Middle lamella First layer of the plant cell wall to be formed during celldivisionMitochondrion Organelle which is the site of aerobic cellular respirationMitosis Cell division of the body cells that results in two identical

daughter cells with the same number of chromosomes asthe original cell

Molecular activity The number of substrate molecules transformed per minute by a single enzyme molecule.

Molecular phylogeny Analysis of different chemicals and genes in differentorganisms to identify interrelationships

Monoamine oxidase A

(MAOA)

Enzyme found in nervous system, liver, and gut that

breaks down monoamine neurotransmittersMonoculture An area containing only one type of genetically very


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of proteins which stimulate the cell cycle and in turn causeuncontrolled cell replication

Oocyte Immature ovumOogenesis Formation of ovaOptical microscope Microscope that uses light to form an imageOrgan Group of tissues grouped into a structure to carry out a

particular functionOrganelle A membrane-bound enclosure in the cytoplasm of a

eukaryotic cell with a particular function, egmitochondria, ribosomes

Osmosis Movement of water down a concentration gradientthrough a partially permeable membrane

Osmotic concentration The concentration of solutes that have an osmotic effectOvary Female sex organ in animals and plantsOvule Female gamete produced in plants

Ovum (plural ova) haploid female gameteOxygenated Containing high levels of oxygen, as in blood from thelungs

Parenchyma Relatively unspecialized plant tissueParthenogenesis Reproduction in which an ovum or ovule develops and

forms a new organism without fusing a male gametePassive transport Transport that does not require energy, such as diffusion

and osmosisPathogen Microorganism that causes diseasePectin A glue-like polysaccharidePentose Sugar Monosaccharide that contains five carbon atoms.Peptide A chain of amino acidsPeptide link The bond formed between two amino acids as a result of a

condensation reactionPreempting organ Organ involved in asexual reproduction which contains

stored food to survive dormant period, eg bulb, cormPeripheral Distant form the center of the bodyPhagocytosis The process by which phagocytes engulf and digest

bacteria or other pathogensPhase 1 trial Trial in which a new drug is given to a small number of

healthy volunteers

Phase 2 trial Trial in which a new drug is given to a small group of volunteer patients affected by the condition the drug isdesigned to treat

Phase 3 trial Trial in which a new drug is used with a large group(5000+) of patients affected by the condition the drug isdesigned to treat

Phenotype The physical and chemical characteristics that make upthe appearance of an organism.

Phenylketonuria (PKU) Genetic condition affecting protein metabolismPhloem Living transport tissue in plants that carries dissolved food

from the leaves around the plant

Phospholipid Lipid molecule containing a phosphate group, making it a polar lipid


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Physical activity level(PAL)

A factor which represents the level of activity undertaken by an individual

Physiological adaptation Adaptations of the biochemistry or physiology of anorganism to the environment in which it lives

Pinocytosis Taking small particles/amounts into a cellPit Gaps in the cell walls that allow communication between

cellsPlacebo An inactive substance that resembles a drug bus has no

action in the bodyPlacebo effect The effect by which patients often improve even when

they are receiving no active drug, they just think they areand it makes them feel better

Placenta In mammals, the organ where nutrients and oxygen fromthe mother pass into the blood of the fetus and waste

products from the fetus pass into the blood of the mother by diffusion. In plants, the pad of tissue which joins theovule to the ovary wall

Placental mammal Mammal in which the young develop inside the uterus of the mother with their need met through the placenta. After

birth they feed on milk from the mammary glandsPlant fiber Long plant cells with heavily lignified cell wallsPlant stanol and sterol Compounds found in plants which reduce levels of LDLs

and balance the LDL/HDL ratio in the bloodPlaque A fatty deposit hardened by calcium salts and fibrous

tissue which may form on the lining of an arteryPlasma Liquid part of blood

Plasmid Extra, circular strand of DNA, separate from the mainchromosome, found in bacteria

Plasmodesmata Sites of intercellular exchanges through cytoplasmic bridges between plant cells

Plasmolysis When the cytoplasm of a plant cell pulls away from thecell wall because it has shrunk through loss of water dueto osmosis

Platelet Component of the blood, a fragment of megakaryocyte,involved in the blood-clotting mechanism

Pleural cavity The space between the pleural membranes surrounding thelungs

Pleural membrane Membrane surrounding the lungsPluripotent Cells with the potential to form most of the cell types

needed in an organismPoint mutation Mutation in one or a small number of nucleotidesPolar lipid Lipid molecule containing a polar groupPollen Male gamete in plantsPollen sac Region of anther where pollen grains developPollen tube Tube which grows out of a pollen grain down the stigma

into the ovule in the ovary to transport the pollen nucleiPollination The arrival of pollen grains on the female part of a flower

Polygenic inheritance Characteristics which are inherited through the interactionof several different genes


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Polymer Molecule made of repeating similar unitsPolypeptide Polymer made of many amino acidsPolysaccharide Polymer made up of many sugar unitsPolyspermy When more than one sperm penetrates the fertile ovumPolyunsaturated fattyacid

Fatty acid that contains more than one double carbon-carbon bond

Population Group of organisms of the same species, living and breeding together in a particular niche in a habitat

Potometer Apparatus used to measure uptake of water by a plantPrecision Exactness: measured in a way which can be reproduced

consistentlyPreimplantation Genetic diagnosis technique by which the genetic make-

up of an embryo can be determined before it is implantedin the uterus of its mother

Prenatal screening Testing a fetus for a genetic condition before birth

Primary cell wall Flexible plant cell walls with cellulose microfibrilsoriented in same directionPrimary structure In proteins, the arrangement of amino acids in the

polypeptide chainsProbability The likelihood of an event happeningProkaryote Single-celled organism which has no nuclear membrane

and the genetic material is not organized intochromosomes

Prophase Second stage of mitosis where the chromosome can coiland condense, when they can take up stain and becomevisible as two chromatids

Prosthetic group A non-protein group attached to a protein moleculeProtein Organic molecules containing carbon, hydrogen, oxygen

and nitrogen along with other elements such as sulfur.Used for growth and repair in the body. Sub-units knownas amino acids

Prothrombin Precursor of thrombin in the blood-clotting cascadeProto-oncogene Gene which codes for proteins which stimulate the cell

cycleProtoplasm The cytoplasm and the nucleus of a cellProtoxylem First xylem tissue to form in a stem rootPulmonary artery Artery carrying deoxygenated blood from the right side of

the heart to the lungsPulmonary circulation Circulation between the heart and the lungsPulmonary veins Vessels carrying oxygenated blood from the lungs back to

the left side of the heartPurine Base in nucleic acids with two-nitrogen containing ringsPyrimidine Base in nucleic acids with one nitrogen-containing ring.Quadrat Apparatus used to identify an area for samplingQuantitative sampling Counting the number of organisms within a measured areaQuaternary structure In proteins, the 3D arrangement of more than one

polypeptide chain in a molecule

Recessive Allele which is only expressed in the phenotype when theindividual is homozygous for the allele.


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different parts of a population, making reproduction between the two groups impossible

Secondary cell wall Inflexible, rigid plant cell wall built up as cellulosemicrofibrils are laid densely at different angles to eachother

Secondary oocyteThe ovum released at ovulation when meiosis has not

been fully completedSecondary structure In proteins, the repeating pattern in the structure of the

polypeptide chains, eg alpha helixSectioning Making thin slices of tissue to prepare a microscopic slideSelection pressure Changes in the environment that mean that certain

characteristics will give an organism an advantageSemiconservativereplication

Replication of DNA where the two strands unzip and newnucleotides align alongside each strand.

Semilunar valves Valves found in veins and the heart that prevent the backflow of blood

Senescence Old ageSeptum An area of two dividing tissue, eg the tissue that divides

the two divides of the heartSerotonin Monoamine neurotransmitter, released when the blood

vessels are damaged which causes the smooth muscles tocontract, narrowing the blood vessel and reducing

bleedingSex chromosome Chromosome that carries information about the sex of the

individualSex pilus Strand of cytoplasm between two bacteria during sexual

reproductionSexual reproduction Production of a new individual resulting from the joining

of two sex cellsSexual selection Selection for features that give reproduction successSingle circulation Circulation where blood is pumped through respiratory

organs and around the body before returning to the heartSite of Special ScientificInterest (SSSI)

Area protected from development because of the scientificvalue of the organism living there

Smooth endoplasmicreticulum (SER)

Endoplasmic reticulum without ribosomes, involved in thesynthesis and transport of lipids

Solute Substance that dissolves in a solvent, such as ionicsubstances in water

Somatic cell Body cellSomatic stem cell Adult cells with a limited ability to form other types of

cellsSpecies Group of closely related organisms that are all potential

capable of interbreeding to produce fertile offspringSpecies richness Measure of the number of species in a given areaSpecificity The property of enzymes which means that they only

catalyse one particular reaction or type of reaction.Spermatogenesis Formation of sperm

Spermatozoa (sperm) Haploid male gameteSphygmomanometer Equipment used for measuring blood pressure


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Spindle Set of microtubules formed during mitosis that move thechromatids to the opposite ends of the cell

Spore Structure produced by asexual reproduction often as a wayof surviving adverse conditions. Develops into a newindividual genetically identical to parent

Sporophyte Diploid generation of plantsSporulation Asexual reproduction that involves the formation of

sporesStaining A method of adding dye to a biological specimen so it

shows up more clearly under the microscopeStandard deviation A statistical measure of the amount of difference form the

mean within a sampleStatin Drug used to lower and balance the cholesterol levels in

the bloodSticky ends The end of a cut DNA helix, with one strand left slightly

longer than the other Stroke An interruption in the function of the brain usually caused

by either a blood clot forming in a blood vessel supplyingthe brain or bleeding from a blood vessel supplying the

brainSuberin Waxy, waterproof compoundSubstrate Substance that enzyme works on.Sulfur bridge Bond between sulfur atoms in two amino acidsSuperior vena cava Major vein carrying deoxygenated blood back from the

head and upper part of the body back to the heartSuspension A solid mixed with a liquid in which the particles will

separate out if the mixture is not constantly moved or stirred

Symplast Interconnected cytoplasm between plant cellsSymplast pathway Pathway through cytoplasm travelled by water molecules

down a concentration gradient by osmosis from soil toxylem as part of transpiration stream

System Group of organs working together to carry out a particular function

Systemic circulation Circulation from the heart around the body and back to theheart

Systole The contraction of the heartSystolic blood pressure The blood pressure reading when the heart is contracting

stronglyTelophase The final stage of mitosis where the chromatids reach the

poles of the cells and become chromosomes, the nuclear membrane reforms and the cytoplasm divides

Temperature coefficient,Q10

The effect of temperature on the rate of a reaction.

Tendinous cords Tendons which prevent the atrioventricular valves turninginside out

Tensile strength Strength to resist pulling forces

Tertiary structure In proteins, the 3D folding of the secondary structureTest cross A genetic cross with the homozygous recessive to show


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whether an individual is homozygous dominant or heterozygous

Testis Male sex organ in humansThalassaemia Genetic disease in which blood proteins are not

manufactured properly, leading to sever anaemia.Thalassaemia major (Cooleys anemia)

Most severe from of beta thalassaemia

Therapeutic cloning Experimental technique aiming to produce embryonicstem cells from an adult to use in therapy for a patient

Thermophilic Heat-lovingThrombin Enzyme that causes the conversion of inactive fibrinogen

to fibrin when the blood clotsThromboplastin Enzyme that controls the conversion of prothrombin to

active thrombinThrombosis Clot that forms in a blood vessel

Thymine A pyrimidine base in DNA.Tissue Specialized cells organized into a group to carry out a particular function

Tissue culture Growth of tissue in the laboratory outside the wholeorganism

Tonoplast The membrane surrounding plant vacuoles which controlsthe movement of substances in and out of the vacuole

Totipotent Cell with the potential to form all known cell types withinan organism

Trachea Windpipe; the tube leading from the nose and mouthdown into the chest, which s supported by incomplete

rings of cartilageTransfer RNA (tRNA) Small unit of RNA that codes for a specific amino acid

and attaches to it in the cytoplasm before carrying it to thesurface of a ribosome for protein synthesis.

Transgenic Organisms which have genes from another organismengineered into their DNA

Translation Process by which the genetic code is converted into new protein molecules directed by RNA.

Translocation Movement of substances around plantsTranspiration The loss of water vapor from the surface of a plantTricuspid valve Valve found between the right atrium and right ventricle

of the heart. One of the atrioventricular valvesTriglyceride A fat or oil containing three fatty acidsTriose sugar Monosaccharide containing three carbon atomsTriplet code Three bases of DNA which code for a single amino acidTriploid Containing three set of chromosomesTrue-breeding When two individual are crossed, all of the offspring show

the same phenotypeTube nucleus Forms of pollen tube for fertilization in plantsTumor An abnormal growth of tissue resulting from the

uncontrolled growth of cells

Tumor suppressor gene Gene which slows down the cell cycle and reduces therate of cell division


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Turgid Swollen, firm; used to describe plant cells that are fullyhydrated

Turgor The point at which the inward movement of water due toosmosis is balanced by the pressure of the plant cell wallson the cytoplasm. The cytoplasm is pressing hard againstthe cell wall

Turnover number The number of substrate molecules transformed per minute by a single enzyme molecule.

Ultrastructure Structure of a cell as revealed by electron microscopeUnit membrane Phospholipid bilayer which is the basis for all living

membranesUnsaturated fatty acid A fatty acid containing at least one double carbon-carbon

bondUracil A pyrimidine base in RNAVacuolar pathway Pathway through cell vacuoles travelled by water

molecules moving down a concentration gradient byosmosis from soil to xylem as part of transpiration stream

Vacuole Membrane-lined enclosure in a cell; permanent feature in plant cells, formed when needed in animal cells

Valid An investigation that is properly designed to answer thequestions which are being asked

Vas deferens Tube carrying sperm out of the testisVector In this context: means of carrying new gene into host

DNA during genetic modificationVegetative propagation Production of new plants by asexual reproductionVein Blood vessel that carriers blood towards the heart

Ventricular systole The contraction of the ventricles of the heart forcing bloodout of the heart to the lungs and around the body

Venule Blood vessel that links a vein and capillaryVesicle Membrane-bound sac containing cellular secretionsVilli Microscopic , finger-like projections which greatly

increase the surface area of the lining of the smallintestines

Vulnerable Facing a high risk of extinction in the wildWhole-chromosomemutations

Mutation resulting in loss or duplication of wholechromosome.

X-ray diffraction Scattering of X-rays by the components of a molecule,used to build up a complex pattern for interpretation of molecular shape.

Xylem Main tissue transporting water from the roots around a plant. The walls of xylem vessels are heavily lignified, allthe older vessels are non-living

Zona pellucida Protective layer of jelly around an animal ovumZygote New diploid cell formed when the two haploid gametes

fuse at fertilization

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