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Transcript of 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