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431 terms

as biology, complete glossary

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Dipeptide
A molecule consisting of two amino acids joined by a peptide bond.
Endocytosis
The process of taking materials into a cell by surrounding them with plasma membrane, which pinches off to form a vesicle inside the cell. This is an active process requiring ATP.
Exchange surface
A specialised area adapted to make it easier for molecules to cross from one side of the surface to the other.
Family
Taxonomic group used in the classification of living organisms. Contains related genera.
Fermenter
A vessel used to grow microorganisms in large numbers.
Gamete
Sex cells, usually haploid (one set of chromosomes). Fuse during sexual reproduction to form zygotes (diploid).
Gene pool
The sum total and variety of all the genes in a population or species at a given time.
Glycosidic bond
The covalent bond formed when carbohydrate molecules are joined together in condensation reactions.
Habitat
The place where an organism or population lives. It includes the climatic, topographic and edaphic factors as well as the plants and animals that live there.
Haem
The iron-containing prosthetic group found in haemoglobin.
Haemoglobinic acid
The acid produced when haemoglobin takes up hydrogen ions.
Haemolysis
The rupturing of animal cell surface membranes, and subsequent release of their contents, when cells placed in a solution of higher water potential and water enters by osmosis.
Health
Complete mental, physical and social wellbeing.
Histone
Type of protein associated with DNA in eukaryotes. DNA is wound around them to form chromatin.
Hormone
Chemicals made in endocrine glands that are carried in the blood to target cells/tissues/organs. They act as chemical messengers.
Hydrocarbon chain
A chain of carbon atoms bonded together with hydrogen atoms bonded onto the carbons.
Immune response
A response to an antigen, which involves the activation of lymphocytes.
Immunological memory
Ability of the immune system to respond very quickly to antigens that it recognises as they have entered the body before.
Incidence
The number of new cases of a disease in a certain time period.
Induced fit (hypothesis)
The theory of enzyme action in which the enzyme molecule changes shape to fit the substrate molecule more closely as it binds to it.
Interferon
A group of factors with non-specific antiviral activity. They also affect the immune system.
Intracellular
Inside the cell.
Ion
An atom (or group of atoms) carrying a positive or a negative charge.
Ionic bond
Attraction between oppositely charged ions.
Keratin
Fibrous protein found in skin, hair and nails.
Lipids
A diverse group of chemicals that includes triglycerides, fatty acids and cholesterol.
Lock-and-key hypothesis
The simple theory of enzyme action where the active site is directly complementary to the substrate molecule.
Lumen
A cavity surrounded by a cell wall in cells, such as xylem vessels, which have lost their cell contents. Also used for the central cavities of blood vessels.
Lymphocyte
A type of white blood cell activated as part of the immune response.
Lysosomes
Membrane-bound vesicles made by pinching off from the Golgi body. They usually contain digestive enzymes.
Macrophages
Large, phagocytic, amoeba-like white blood cells that engulf, ingest and destroy bacteria, damaged cells and worn-out red blood cells.
Magnification
The number of time greater an image is than the object.
Messenger RNA (mRNA)
A type of RNA polynucleotide involved in protein synthesis. Carries the information coding for a polypeptide from the nucleus to the ribosomes in the cytoplasm.
Microtubule motors
Proteins associated with microtubules. The proteins can move along microtubules. Kinesin moves towards the (+) end of the microtubules and dynein moves towards the (-) end.
Mitosis
Nuclear division that results in the formation of cells that are genetically identical to the parent cell.
Monoculture
A crop of plants of a single species bred to be very similar.
Monomer
A small molecule that is one of the units bonded together to form a polymer.
Monosaccharide
A simple sugar molecule. The monomer of polysaccharides.
Morbidity
The proportion of people in a population who are ill with a particular disease at any one time.
Mortality
The number of people who die from a disease in a certain time period.
Mucus
A slimy substance secreted by goblet cells in animal epithelial tissues. It is made up mostly of glycoproteins and protects and/or lubricates the surface on to which it is secreted.
Mutation
A change in the structure of DNA, or in the structure and number of chromosomes.
Mycelium
The mass of filaments (hyphae) that make up the body of a fungus.
Natural selection
The mechanism for evolution in which the best-adapted organisms in a population can outcompete those that are less well-adapted.
Niche
The exact role of an organism in the ecosystem - its use of the living and non-living components of the ecosystem.
Non-competitive inhibitor
An inhibitor of an enzyme-controlled reaction that binds to the enzyme molecule in a region away from the active site.
Nuclear envelope
The double membrane structure surrounding the nucleus in eukaryotic cells.
Nucleotide
The monomer of nucleic acids consisting of a phosphate, a sugar and an organic base.
Nucleus
A large, membrane-bound organelle found in eukaryotic cells, which contains the genetic material in the form of chromosomes.
Nutrition
The total substances taken into an animal or plant for use in metabolism (the sum total of its diet).
Oestrogen
Steroid hormone made in ovaries.
Omnivore
An animal that eats plant and animal material.
Opportunistic infection
Infection caused by an organism that infects a host with a weakened (compromised) immune system.
Organ
A collection of tissues that work together to perform a specific overall function or set of functions within a multicellular organism.
Organelle
Structure inside a cell. Each has a specific function and many are surrounded by membrane.
Organic base
Nitrogenous coompound in nucleic acid: adenine, thymine, uracil, cytosine, guanine are examples.
Oxygen tension
The amount of oxygen in the air expressed as the pressure created by the presence of oxygen, expressed in kilopascals (kPa).
Oxygenated
Describes blood carrying oxygen in the form of oxyhaemoglobin.
Oxyhaemoglobin
Haemoglobin with oxygen molecules attached.
Pandemic
Describes a disease that is spreading worldwide or over continents.
Parenchyma
Relatively unspecialised plant cells. They have living contents and thin, permeable cellulose cell walls. They may be able to photosynthesise, store food or support young plants.
Partial pressure
The proportion of total pressure provided by a particular gas as part of a mixture of gases.
Partially permeable membrane
A membrane that will allow some molecules to pass through but will not allow some others to pass through.
Passive immunity
Immunity acquired indirectly without activation of the lymphocytes, such as through the placenta, from breast milk, or by injection.
Pathogen
An organism that causes disease.
Peptide
A molecule consisting of a small number of amino acids bonded together by (covalent) peptide bonds.
Peptide bond
The covalent bond formed when amino acids are joined together in condensation reactions.
Peristalsis
Muscular contractions of muscle layers of gut to squeeze food along.
pH
Gives measure of acidity/alkalinity of a solution. It is the reciprocal of the logarithmic value of the hydrogen ion concentration.
Phagocyte
A cell that can carry out phagocytosis and ingest bacteria or small particles. Macrophages and neutrophils are phagocytes.
Phagosome
A vacuole inside a phagocyte which is created by an infolding of the plasma (cell surface) membrane to engulf a foreign particle. The foreign particle is held inside this.
Phloem
A tissue in plants that is used to transport dissolved sugars and other substances.
Phospholipid
A molecule consisting of a glycerol molecule, two fatty acid molecules and a phosphate group covalently bonded together. Forms the basis of cell membranes.
Photosynthesis
Process by which plants, some bacteria and some protoctists make food using carbon dioxide, water and sunlight energy.
Phylogeny
The evolutionary relationships between organisms.
Phylum
A taxonomic group used in classification of living organisms. Contains similar classes.
Pinocytocis
The process of endocytosis involving the bulk movement of liquids into a cell.
Pits (or bordered pits)
Thin areas in the lignified walls of xylem tissue cells that allow communication between adjacent cells.
Plaque
Fatty material built up under the endothelium of an artery.
Plasma cells
Mature B-lymphocytes (white blood cells) that secrete a specific kind of antibody.
Plasma proteins
Proteins made in the liver that are found in the non-cellular fraction of the blood.
Plasmid
Small, circular piece of DNA present in some bacterial cells. May have genes for antibiotic resistance and can also be used as vectors in genetic engineering.
Plasmodesma(ta)
A fine strand of cytoplasm that links the protoplasm of adjacent cells through a thin area of cell wall called a pit.
Plasmolysis
Detachment of the plasma membrane from the cell wall as the cytoplasm shrinks when water is lost from a plant cell.
Platelets
Fragments of cells in the blood that play a part in blood clotting.
Pluripotent
Stem cells capable of differentiating to become a limited number of cell types found in the organism (e.g. cells of an early embryo).
Polymer
A large molecule made up of many/repeating similar, smaller molecules (monomers) covalently bonded together.
Polynucleotide
A polymer consisting of many nucleotide monomers covalently bonded together (DNA and RNA are examples).
Polypeptide
A polymer consisting of many amino acid monomers covalently bonded together.
Polysaccharide
A polymer consisting of many monosaccharide monomers covalently bonded together.
Potometer
Apparatus used to measure water uptake in a leafy shoot and so to estimate rate of transpiration.
Precipitate
A suspension of small solid particles in a liquid, produced by a chemical reaction.
Prevalence
The number of people with a particular disease at a certain time.
Primary defences
The defences that prevent the entry of a pathogen into the body.
Primary structure
The sequence of amino acids found in a protein molecule.
Prokaryote
An organism with cells that do not contain a true nucleus.
Prophase
The phase of mitosis where the chromosomes become visible as a pair of sister chromatids joined at the centromere.
Prosthetic group
A non-protein organic molecule that forms a permanent part of a functioning protein molecule.
Protease
An enzyme capable of digesting proteins.
Protein
A polymer consisting of many amino acid monomers covalently bonded together.
Pulmonary circulation
The circulation of the blood through the lungs.
Pulmonary vein
The vein carrying oxygenated blood from the lungs to the left atrium of the heart.
Purine
Adenine and guanine - nitrogenous bases consisting of a double ring structure.
Purkyne tissue (Purkinje tissue)
Specialised tissue (muscle fibres) in the septum of the heart that conducts the electrical stimulus from the sinoatrial node to the ventricles.
Pyrimidine
Thymine, cytosine and uracil - nitrogenous bases consisting of a single ring structure.
Quadrat
A square frame used for sampling in field work.
Qualitative
A study is that does not involve quantity (numbers). For example, simple observations to see if a particular species lives in a selected area.
Quantitative
A study involving quantity (numbers). For example, if you count the number of individuals of a species in a selected area.
Quaternary structure
Protein structure where a protein consists of more than one polypeptide chain e.g. Haemoglobin and insulin.
Receptor sites
Protein or glycoprotein molecules on cell surfaces, used for attachment of specific substances such as hormones or viruses.
Reducing sugar
A carbohydrate monomer or dimer that gives a positive result in Benedict's test because it is able chemically to reduce copper sulfate in solution.
Reduction
Chemical reaction involving the gain of electrons or the addition of hydrogen.
Resolution
The ability to distinguish two separate points as distinct from each other.
Respiration
The process in which energy is released from complex molecules, such as glucose, within cells and transferred to molecules of ATP.
Ribose
The 5-carbon (pentose) sugar found in RNA nucleotides.
Ribosomal RNA (rRNA)
The nucleic acid found in ribosomes.
Ribosome
The organelle on which proteins are synthesised inside the cell.
Risk factor
A factor that increases the chance that you may develop a particular disease.
RNA
A single-stranded polynucleotide molecule that exists in three forms. Each form plays a part in the synthesis of proteins within cells.
Root hair cells
Cells in the epithelium of roots that have long extensions to increase surface area for the absorption of water and minerals.
Secondary defences
Defences that attempt to kill or inactivate pathogens that have already invaded the body.
Secondary structure
The local coiling or folding parts of a protein molecule due to the formation of hydrogen bonds formed as the protein is synthesised. E.g. a-helix and b-pleated sheets.
Secretion
The release of a substance made inside the cell using the process of exocytosis.
Selection pressure
An external pressure that drives evolution in a particular direction.
Semi-conservative replication
The replication of a DNA strand where the replicated double helix consists of one old strand and one newly synthesised strand.
Semilunar valves
Valves between the ventricles and the main arteries leading out of the heart, which prevent backflow of blood.
Septum
The wall separating the ventricles of the heart.
Sexual reproduction
Production of a new individual formed by the fusing of gametes from two different parents so that the offspring have a unique combination of alleles from both parents.
Sieve tube element
A cell in phloem tissue through which sap is transported. It has very little cytoplasm, no nucleus, and non-thickened cellulose cell walls, with the end walls perforated.
Simple diffusion
The movement of molecules from a region of their higher to lower concentration.
Single circulatory system
A circulation in which blood flows through the heart once during each circulation of the body.
Sink
A part of a plant that removes sugars from the phloem.
Sinoatrial node (SAN)
The patch of tissue that initiates the heartbeat by sending waves of excitation over the atria.
Smooth muscle
A type of muscle (involuntary muscle) found mostly in certain internal organs and involved in involuntary movements such as peristalsis.
Solute
A solid that dissolves in a liquid.
Solute potential (Ys)
The component of water potential that is due to the presence of solutes - the potential energy of a solution provided by the solutes.
Solution
Liquid with dissolved solids.
Solvent
A liquid that dissolves solids.
Source
A part of the plant that releases sugars into the phloem.
Speciation
The formation of a new species.
Species
A group of organisms whose members are similar to each other in shape, physiology, biochemistry and behaviour, and can interbreed to produce fertile offspring.
Spindle
A structure consisting of protein fibres found in eukaryotic cells during cell division. They guide the movement of chromosomes to opposite end of the cell at telophase.
Starch
A polysaccharide found in plant cells. It is formed from the covalent bonding together of many glucose molecules.
Stem cells
Undifferentiated cells that are capable of becoming differentiated to a number of possible cell types.
Stoma (pl: stomata)
Pore in leaf epidermis, surrounded by two guard cells. Changes in turgidity of the guard cells can open or close the stoma. Allow gaseous exchange and transpiration in plants.
Stroma
The gel-like matrix found in chloroplasts. The membranes of the thylakoids/grana are embedded in it.
Substrate
The substance that is used up in an enzyme-controlled reaction, leading to the formation of product. It fits into the active site of the enzyme at the start of the reaction.
Surface tension
The 'skin' on the surface of water formed as a result of hydrogen bonding in water molecules pulling the surface molecules downwards.
Surfactant
A chemical that can reduce the surface tension of a film of water.
Sustainable development
Development that does not cause excessive harm to the surrounding environment. The local biodiversity and people can continue to live and operate alongside the development.
Sympatric
Speciation that occurs within one area - some factor other than geographical separation has prevented free interbreeding between members of the species.
Symplast pathway
The route taken by water through the cytoplasm of cells in a plant.
Systemic circulation
The circulation that carries blood around the body, excluding the circulation to the lungs.
Systole
The stage of the heart cycle in which heart muscle contracts to pump blood.
Taxon (pl: taxa)
A taxonomic group, such as a class or a family, used to aid classification.
Taxonomy
The study of the principles behind classification.
Telophase
Final phase of mitosis. Two new nuclear envelopes form around the two new nuclei.
Tendinous cords
String-like tendons used to attach the atrioventricular valves of the heart to the sides of the ventricle wall. Sometimes called heart strings.
Tertiary structure
The overall three-dimensional shape of a protein molecule. Involves hydrogen bonding, disulfide bridges, ionic bonds and hydrophobic interactions.
Testosterone
Steroid hormone made in the testes.
Thrombus
A blood clot.
Thylakoid
Flattened membrane sacs in chloroplasts, which hold the pigments used in photosynthesis and are the site of the light reactions. A stack of thylakoids forms a granum.
Thymine
A nitrogen-containing organic base found in DNA. It pairs with adenine.
Tissue
A group of similar cells that perform a particular function.
Tissue fluid
The fluid, derived from blood plasma, that surrounds the cells in a tissue.
Totipotent
Undifferentiated cell that is capable of differentiating into any kind of specialised cell.
Trachea
The windpipe leading from the back of the mouth to the bronchi.
Transcription
The assembly of an mRNA molecule that is a copy of the DNA coding strand (and complementary to the template strand).
Transect
A line through a habitat used to help take samples and study the habitat.
Transfer RNA (tRNA)
A type of polynucleotide involved in protein synthesis. It transports amino acids to the ribosomes to be added to the growing polypeptide chain.
Transgenic
Organism that has genetic material from another organism, usually by genetic engineering.
Translocation
The movement of sucrose and other substances up and down a plant.
Transmission
The way in which a microorganism or other pathogen travels from one host to another.
Transpiration
The loss of water vapour from the aerial parts of a plant due to evaporation.
Triglyceride
A molecule consisting of a glycerol molecule and three fatty acid molecules covalently bonded together.
Turgid
Describes a cell that is full of water as a result of entry of water due to osmosis such that pressure of the cell wall prevents more water entering.
Ultrastructure
The detailed structure of the internal components of cells as revealed by the electron microscope rather than by the light microscope.
Uracil
A nitrogen-containing organic base found in RNA. Pairs with adenine.
Urea
Chemical made in the liver from amine groups from deaminated amino acids and carbon dioxide. It is toxic and is removed from the body in urine.
Vaccine
A preparation of antigens given to provide artificial immunity.
Vacuolar pathway
The pathway taken by water in plants as it passes from cell to cell via the cell cytoplasm and vacuole.
Variable
Condition in an experimental investigation. Can be independent (altered by the experimenter) or dependent (respond to changes in the independent variable).
Variation
The differences between individuals.
Vascular tissue / bundle
The transport tissue in a plant - usually found as a bundle containing both xylem and phloem.
Vector
An organism that carries a disease-causing organism (pathogen) from one host to another. Also describes an agent (such as a plasmid) that can transfer genetic material.
Vena cava
Either of two large veins that carry deoxygenated blood from the body back to the heart.
Ventilation
Breathing - movement of diaphragm and rib cage that bring air into and out of the lungs.
Ventricles
The lower chambers in the heart.
Vesicle
A membrane-bound sac found in cells and used to transport materials around the cell.
Villi
Folds in the wall of an organ or tissue that increase surface area.
Vitamin
Chemical needed in small amounts for healthy metabolism. Some organisms can make them, some organisms have to obtain them in the diet.
Water potential (Y)
A measure of the ability of water molecules to move freely in solution. Decreased by the presence of solutes.
Water vapour potential
The potential energy of water vapour in a gas - it is used to indicate how much water vapour is present.
Xerophyte
A plant specially adapted to living in dry areas.
Xylem
A plant tissue containing vessels (and other cells) that are used to transport water in a plant and provide support.
Zygote
Diploid cell made from fusion of male and female gametes.
Abundance
The frequency of occurrence of plants in a sampled area, such as a quadrat.
Activation energy
The level of energy required to enable a reaction to take place. Enzymes reduce the amount of energy required to allow a reaction to proceed.
Active immunity
Immunity that is acquired by activation of immune system.
Active site
The area on an enzyme molecule to which the substrate binds.
Adhesion
Force of attraction between molecules of two different substances.
a-helix
A protein secondary structure - a right-handed spiral held in place by hydrogen bonds between adjacent C=O and NH groups.
Allopatric
Speciation due to organisms of a species being separated by geographical barriers so that eventually they become so different that they cannot interbreed.
Amino acid
An organic compound that contains both an amino group(-NH2) and a carboxyl group (-COOH). The monomers of protein molecules.
Amylase
An enzyme that catalyses the hydrolysis of starch to maltose.
Active transport
Movement of substances across membranes against their concentration gradient, requiring the use of energy in the form of ATP.
Allele
A version of a gene.
Antigen-presenting cell
A macrophage that has ingested a pathogen and displays some of the pathogen's molecules on its cell surface membrane.
Apoplast pathway
The route taken by water between the cells or through the cell walls in a plant.
Amylose
Part of a starch molecule, consisting of many thousands of glucose residues bonded together.
Assimilation
Term usually applied to the process of incorporating simple molecules of food produced by digestion into the living cells of an animal for use in metabolism.
Assay
The use of comparative studies or samples to determine the concentration or quantity of a substance in a sample.
Adenine
A nitrogen-containing organic base found in nucleic acids. It pairs with thymine in DNA and with uracil in RNA.
Autotroph
An organism that makes its own food from simple inorganic molecules, such as carbon dioxide and water.
Antibodies
Protein molecules released by the immune system in response to an antigen, which are capable of neutralising the effects of the antigen.
Asexual reproduction
The production of genetically identical new organisms by a single 'parent' organism.
Base-pairing rules
Rules governing the complementary bases in nucleic acids. Adenine pairs with thymine (or uracil). Guanine pairs with cytosine.
Adipose
Describes tissue consisting of cells that store fat/lipid.
Atrium
One of the upper chambers in the heart.
ATP
A molecule used to store energy temporarily in organisms. The molecule is broken down to adenosine diphosphate + phosphate to release energy to drive metabolic processes.
Arteriosclerosis
Hardening of the artery walls and loss of elasticity caused by atherosclerosis or by deposition of calcium.
Biuret test
A biochemical test for the presence of proteins.
Bronchi
Airways in the lungs that lead from the trachea to the bronchioles.
Artificial immunity
Immunity acquired as a result of deliberate exposure to antigens or by the injection of antibodies.
Atherosclerosis / atheroma
The process of deposition of fatty substances in the lining of arteries to form atheroma, which may eventually lead to arteriosclerosis (hardening of the arteries).
Cardiac muscle
The muscle found in the heart. It has its own intrinsic heartbeat (it is myogenic).
Carrier protein
A protein found in membranes, which is capable of carrying a specific molecule or ion through the membrane by active transport.
Calibration
To use known concentrations of a substance in a solution to make a standard curve on a graph. This can be used to determine the amount of that substance in solutions of unknown concentration.
Centromere
The region of a chromosome where two sister chromatids are joined together, and where the spindle fibre attaches during cell division.
Cellulose
A carbohydrate polymer (of b-glucose) that forms plant cell walls.
Atrioventricular node (AVN)
A patch of tissue in the septum of the heart that conducts the electrical stimulus from the atria in the heart through to the Purkyne fibres.
Cartilage ring
A flexible ring of cartilage that holds the airways open.
Chromatin
Material staining dark red in the nucleus during interphase. It consists of nucleic acids and proteins. Condenses into chromosomes during prophase of nucler division.
Benedict's test
Test for reducing sugars. Sample is heated to 80ºC with reagent. If a reducing sugar is present, the reagent changes from blue to red precipitate.
Cardiac cycle
The sequence of events making up one heartbeat.
Anomalous
Describes a result/data point that does not appear to fit the pattern of the other results.
Clones
Genetically identical cells or individuals.
Chloride shift
The movement of chloride ions into red blood cells to balance the loss of hydrogencarbonate ions.
Adaptation
Feature of a living organism that increases its chances of survival, for example thick fur on an animal that lives in a cold habitat.
Centriole
An organelle from which the spindle fibres develop during cell division in animal cells.
Antigen
A foreign molecule (which may be protein or glycoprotein) that can provoke an immune response.
Artificial selection
Also called selective breeding - the process of improving a variety of crop plant or domesticated animal by breeding from individuals with desired characteristics.
Cohesion
The attraction between water molecules due to hydrogen bonding.
Cambium
Plant tissue in the stem and root that contains dividing cells.
Anaphase
In mitosis, the stage when the newly separated chromatids are pulled towards opposite poles of the nuclear spindle.
Carnivore
An animal that eats meat.
Cell surface membrane
Also known as the Plasma membrane.
Cartilage
A flexible, slightly elastic connective tissue.
Cytokines
Hormone-like proteins produced by vertebrates, which are used for communication between cells, allowing some cells to regulate the activities of others.
Cytoskeleton
The network of protein fibres and microtubules found within the cell that gives structure to the cell and is responsible for the movement of many materials within it.
Cholesterol
A lipid molecule (not a triglyceride) found in all cell membranes and involved in the synthesis of steroid hormones.
Casparian strip
A strip of waterproof material (suberin) in the cell walls of root endodermis cells. It blocks the apoplast pathway.
Bronchioles
Airways in the lungs that lead from the bronchi to the alveoli.
Buffer
A chemical system that resists changes in pH by maintaining a constant level of hydrogen ions in solution. Certain chemicals dissolved in the solution are responsible for this.
Constrict
To make narrow. For example, in the narrowing of blood vessels.
Clonal expansion
The division of selected cells by mitosis to increase their numbers.
Clonal selection
The selection of cells (of the immune system) with a specific receptor site. These cells will undergo expansion as part of the immune response.
Cytokinesis
The division of the cell, following nuclear division, to form two new cells.
Chromosome
A linear DNA molecule wrapped around histone proteins found in the nucleus. Become visible in prophase of cell division.
Crenation
State of animal cells when they have been immersed in a solution of lower water potential and have lost water by osmosis and become shrivelled.
Catalyst
A substance that increases the rate of a reaction but does not take part in the reaction, and so is re-usable.
Carcinogen
A substance that causes cancer.
Cristae
The folds found in the inner membrane of a mitochondrion. Stalked particles containing ATP synthase are found here.
Binomial system
A system of naming living things using two Latin words - the genus name and the specific name.
Continuous variation
Variation where there is a range of intermediates, such as height, hair colour and intelligence in humans. Affected by multiple genes and environment
Electrocardiogram
Trace (graph) showing the electrical activity of the heart muscle (atria and ventricles) during a cycle.
Ciliated epithelium
Lining cells that have cilia on their cell surface.
Domain
Classification level introduced by Carl Woese dividing the kingdom Prokaryotae into two and placing all Eukaryotes into a third.
Connective tissue
A type of tissue that consists of separate cells held together by a ground substance (matrix).
Cofactor
A molecule or ion that helps an enzyme to work. It may be an inorganic ion or an enzyme.
Enzyme
A protein molecule that acts as a biological catalyst.
Discontinuous variation
Variation between living organisms within a species, where there are discrete categories and no intermediates, e.g. blood groups A, B, AB or O in humans.
Disease
A departure from full health.
Covalent bond
A chemical bond formed by the sharing of one or more electrons between two atoms.
Bohr shift / Bohr effect
The effect of carbon dioxide concentration on the affinity of haemoglobin for oxygen.
Disaccharide
A molecule consisting of two monosaccharide sugars joined by a glycosidic bond.
Endemic
Describes a disease that is always present in an area. May also mean a species that is found only in a particular area and nowhere else.
Evolutionary distance
A measure of how far apart two organisms are on the evolutionary scale.
Affinity
An attractive force between substances or particles.
Antibiotics
Molecules produced by microorganisms that kill or limit the growth of other microorganisms
Atrioventricular valves
Valves between the atria and ventricles that prevent backflow of blood.
Binary fission
Method of cell division in bacteria. The DNA replicates and the cell divides into two, each having the same DNA as the parent cell.
Biodiversity
The number and variety of living things to be found in the world, in an ecosystem or in a habitat.
Carbohydrate
A class of biological molecules with the general formula Cx(H2O)y. It includes sugars, starches, glycogen and cellulose.
Alveoli
Small air sacs in the lungs.
Chlorophyll
Pigments found in chloroplasts of plant (and some protoctist) cells. Each molecule consists of a hydrocarbon tail and a porphyrin ring head with a magnesium atom.
Chromatid
A replicated chromosome appears as two strands in early stages of cell division. Each strand is called a.....
Cilia
Short extensions of eukaryotic cells, typically 2-10 µm long and 0.03 µm in diameter. Used for locomotion or to move fluids or mucus over a surface.
Body mass index
Numerical value found by dividing an individual's mass in kg by the (height in m)2 and used to assess if the individual is underweight, acceptable weight, overweight or obese.
Chemotaxis
The movement of cells or organisms towards or away from a particular chemical.
Complementary
Refers to structures that fit together because their shapes and/or charges match up. For example, adenine and cytosine in DNA.
Concentration gradient
The difference in concentration of a substance between two regions.
Class
Taxonomic group used in classification of living organisms. Below phyla but containing orders (consisting of families, genera and species).
Cortex
Tissue in plant roots and stems between epidermis and vascular tissue.
Coronary arteries
Vessels that carry blood to the heart muscle.
Carbaminohaemoglobin
The molecule resulting from combination of carbon dioxide and haemoglobin.
Deoxyribose
The 5-carbon sugar in DNA nucleotides.
Companion cell
A cell in the phloem involved in actively loading sucrose into the sieve tube elements, to which it is linked by many plasmodesmata.
Control
Part of an experimental investigation - set up to show that the variable being investigated is responsible for the change observed.
Diaphragm
A sheet of muscular and fibrous tissue separating the chest cavity from the abdominal cavity.
Cell signalling
Processes that lead to communication and coordination between cells. Hormones binding to their receptors on the cell surface membrane are an example.
Deoxygenated
Blood with haemoglobin that carries no or little oxygen.
Cytosine
A nitrogen-containing organic base found in nucleic acids. It pairs with guanine in DNA.
Condensation
A type of chemical reaction in which two molecules are joined together by means of a covalent bond to form a larger molecule, and at the same time a water molecule is released.
Dilate
To make wider. For example, when the lumens of blood vessels become wider.
Dissociation
The separation of a molecule into two molecules, atoms or ions without breakage of a covalent bond. For example, the release of oxygen from oxyhaemoglobin.
Conservation ex situ
Conservation in areas other than the natural habitat.
Cotransporter
A protein in a cell membrane that allows movement of one molecule when linked to the movement of another molecule in the same direction by active transport.
Emulsion
A suspension of one material in another as droplets, because it does not dissolve. For example, fat droplets dispersed in water.
Endodermis
A ring of cells between the cortex of a root and the area housing the xylem and phloem.
DNA
A polymer of nucleotide molecules that form the instructions for the synthesis of proteins found within organisms. These nucleotides contain the 5-carbon sugar deoxyribose.
Epidemiology
The study of patterns of disease and the factors that influence their spread.
Enzyme-substrate complex
The intermediate structure formed when a substrate molecule binds to an enzyme molecule.
Deamination
Removal of amine (NH2) group from an amino acid
Endothelium
A tissue that lines the inside of a structure, such as a blood vessel.
Evolution
Process by which the present diversity of living organisms arose from simple primitive organisms, with new species arising by natural selection.
Diastole
The period when the heart muscle in the ventricles is relaxing and blood pressure is at its lowest.
Elastic tissue
Tissue containing the protein elastin, which is able to stretch and recoil.
Coenzyme
An organic non-protein molecule that binds temporarily with substrate to an enzyme active site. It is essential for enzyme activity.
Calibration
To determine the value of intervals of a scale on an instrument, such as a thermometer.
Chloroplast
An organelle found in plants, which contains chlorophyll and is responsible for photosynthetic activity in the plant.
Classification
The organisation of living organisms (or other items) into groups according to their shared similarities.
Collagen
A structural fibrous protein found in connective tissue, bones, skin and cartilage. It accounts for 30% of body protein.
Competitive inhibitor
A substance that reduces the rate of an enzyme-controlled reaction by binding to the enzyme's active site.
Diffusion
The net movement of molecules or ions in a gas or liquid from an area of high concentration to an area where they are less concentrated.
Channel protein
A protein pore that spans a membrane, through which very small ions and water soluble molecules may pass.
Dissociation curve
The curve on a graph showing the proportion of haemoglobin that is saturated with oxygen at different oxygen tensions.
Division of labour
Any system where different parts perform specialised functions, each contributing to the functioning of the whole.
Double circulatory system
A transport system in which blood travels twice through the heart for each complete circulation of the body.
Conservation in situ
Conservation in the natural habitat.
Diploid
Cells or organisms that have two copies of each chromosome in their nuclei.
End-product inhibition
The regulation of metabolic pathways where the last product in a sequence of enzyme-controlled reactions becomes an inhibitor of one of the enzymes earlier in the sequence.
Environmental impact assessment
An assessment of the damage that may be caused to the (local) environment by a proposed development.
Double helix
Describes the structure of DNA, a twisted helix of two strands with bases joining the strands.
Ester bond
The bond formed when fatty acid molecules are joined to glycerol molecules in condensation reactions.
Erythrocytes
Red blood cells.
Differentiation
The development and changes seen in cells as they mature to form specialised cells.
Extinction
The death of the last individual in a species.
Endoplasmic reticulum (ER)
A series of membrane-bound, flattened sacs extending from the outer nuclear membrane through the cytoplasm. Comes in rough and smooth forms.
Epithelium
A tissue that covers the outside of a structure.
Extracellular
Outside the cell - for example describes enzymes that work outside the cell.
Diffusion gradient
The difference in molecular concentration that allows diffusion to occur.
Exocytosis
The process of removing materials from the cell by fusing vesicles containing the material with the plasma membrane .
Eukaryote
An organism having cells with a nucleus and membrane-bound organelles.
Enzyme-product complex
The intermediate structure in which product molecules are bound to an enzyme molecule.
Fertiliser
A substance added to soil to enhance the growth of plants.
Flaccid
A term used to describe plant tissue where the cells have lost turgor and are not firm.
Epidemic
Describes a disease that spreads to many people quickly and affects a large proportion of the population.
Ethanol emulsion test
A biochemical test for the presence of lipids.
Genus
Taxonomical group used in the classification of living organisms. Contains similar species.
Glucose
A 6-carbon monosaccharide sugar. Very important source of energy within cells. Substrate for glycolysis.
Gaseous exchange
The movement of gases by diffusion across a barrier such as the atreous wall.
Guard cells
In pairs, these form the stomatal pore in the epidermis plants. They control the opening and closing of the pore by changes in their turgidity.
Golgi body
Membrane-bound organelle in eukaryote cells. Involved in the modification and transport of proteins.
Eukaryotic cell
Cells that have a nucleus inside a nuclear envelope, and other membrane-bound organelles.
Glycogen
A polysaccharide found in animal cells. Formed from the bonding together of many glucose molecules, used as a store of glucose.
Herbivore
An animal that eats plant material.
Facilitated diffusion
The passive movement of molecules across membranes down their concentration gradient. Aided by transport proteins but no metabolic energy is required.
Genome
All the genetic material inside an organism (or cell).
Elastic fibres
Long fibres of the protein elastin that have the ability to stretch and recoil.
Hydrophilic
Associating with water molecules easily (water-loving).
Haemoglobin
The protein that carries oxygen in the red blood cells.
Denaturation
An irreversible change in the tertiary structure of a protein molecule. It leads to loss of function in most proteins.
Guanine
A nitrogen-containing organic base found in nucleic acids. It pairs with cytosine.
Endotherm
An animal that produces heat within its cells, from respiration, to maintain a constant body temperature.
Epidermis
Outer layer(s) of cells of a multicellular organism.
Hyphae
The strands that make up the body of a fungus.
Gated channels
Protein channels found in cell membranes, which can be opened or closed in response to cell signals.
Ecosystem
All the living organisms and all the non-living components in a specific area, and their interactions.
Globular proteins
Proteins with relatively spherical molecules, soluble in water, often having metabolic roles in organisms.
Goblet cells
Mucus-secreting cells in epithelial tissue.
Glycerol
A 3-carbon (alcohol) molecule. It forms the basis of lipids when fatty acids are bonded to it.
Lactate
The ionised form of the product of anaerobic respiration in mammals and some bacteria.
Lignin
A waterproofing substance that impregnates the walls of xylem tissue. Lignin gives wood its strength.
Haploid
A cell or organism that has one set of chromosomes/one copy of each chromosome.
Glycolipid
A lipid with carbohydrate molecules attached.
Fluid mosaic (model)
The model of cell membrane structure proposed by Singer and Nicholson - a phospholipid bilayer with proteins 'floating' in it.
Food tests
Simple procedures that show the presence of various biological molecules in samples or structures.
Interleukin
Cell-signalling chemicals. Some are involved in activating cells of the immune system. A type of cytokine.
Hydrogen bond
A weak bond formed between partially charged atoms. It is seen in water molecules, and is important in the secondary and tertiary structure of proteins.
Hydrolysis
A reaction in which a molecule is broken down into two smaller molecules by the addition of a water molecule and the breaking of a covalent bond.
Lacteal
A blind-ending branch of the lymph system found in each villus of the small intestine.
Heterotroph
Organism that gains nutrients from complex organic molecules. These molecules are digested by enzymes to simple soluble molecules.
Kinetic energy
Energy of movement.
Glycoprotein
A protein with carbohydrate molecules attached.
Genetic erosion
The loss of genetic variation due to (artificial) selection.
Kingdom
Taxonomic group. Living organisms are grouped into one of five: Prokaryotae, Protoctista, Fungi, Plantae and Animalia.
Fat
Mixture of lipids, mainly triglycerides with saturated fatty acids, that is solid at body temperature. Act as an energy store, insulation, waterproofing and may give buoyancy.
Interphase
The phase of the cell cycle where synthesis of new DNA and organelles takes place.
Monokines
Chemical produced by monocytes to signal to other cells. Also called lymphokines.
Homologous
Chromosomes in diploid organisms that have the same genes at the same loci and that pair up during meiosis. Can also refer to structures that have a common evolutionary origin.
Microtubules
Components of the cell cytoskeleton. Involved in mitosis, cytokinesis and movement of vesicles within cells.
Initial reaction rate
Rate of reaction at the beginning before a significant amount of product has been formed or reactant used up.
Hydrostatic pressure
Pressure created by a fluid pushing against the sides of a container.
Myogenic
Describes muscle tissue (heart muscle) that generates its own contractions.
Meiosis
Nuclear division that results in the formation of cells containing half the number of chromosomes of the adult cell.
Memory cells
B and T cells that remain in the body after an immune response. Their presence enables a much faster and greater second immune response.
Keratinocytes
Cells that make keratin.
Fibrous protein
A protein with a relatively long, thin structure, which is insoluble in water and metabolically inactive, often having a structural role within the organism.
Marker-assisted selection
Used by animal and plant breeders to help select individuals with the desired genotype. The desired gene is linked to a section of DNA that is easy to identify in a young individual.
Monophyletic
A group of organisms that share a common ancestor and therefore belong to the same classification group.
Omnipotent
Another word for totipotent.
Nucleic acid
A polymer of nucleotide molecules.
Diversity
Term used to describe a large range of species in an area or a population of organisms that have significant genetic variation.
Metabolism
All the chemical reactions that take place in an organism.
Osmosis
The movement of water molecules from a region of higher water potential to a region of lower water potential across a partially permeable membrane.
Lymphatic system
A system of lymph nodes and lacteals with lymph fluid.
Myoglobin
A respiratory pigment (protein) with a higher affinity for oxygen than haemoglobin.
Metaphase
The phase of mitosis where the chromosomes line up at the equator of the spindle.
Microvilli
Folds in the membrane of a cell that increase its surface area.
Maltose
A disaccharide molecule consisting of two a-glucose molecules bonded together.
Limiting factor
A variable that limits the rate of a process. If it is increased, then the rate of the process will increase.
Macromolecule
A very large molecule.
Intercostal muscles
Muscles between the ribs, responsible for moving the rib cage during breathing.
Fibrillation
A state in which the chambers in the heart contract out of rhythm.
Inhibition/inhibitor
The slowing of an enzyme-controlled reaction by a molecule that slows down or prevents the formation of enzyme-substrate complexes.
Plasma membrane or cell surface membrane
The membrane that surrounds every cell, forming the selectively permeable boundary between the cell and its environment.
Gene
A length of DNA that carries the code for the synthesis of one (or more) specific polypeptide(s).
Mitochondrion
The organelle found in cells in which most of the ATP synthesis occurs. It is the site of aerobic respiration.
Meristem cells
Undifferentiated plant cells capable of rapid cell division.
Natural immunity
Immunity acquired through exposure to disease during the normal course of life.
Hydrophobic
Water-repelling (water-hating).
Neutrophils
Phagocytic white blood cells. They engulf and digest bacteria. They have a many-lobed nucleus, and a granular cytoplasm due to the large numbers of lysosomes present.
Lipase
An enzyme that catalyses the breakdown of lipid molecules.
Parasite
An organism that lives in or on another living organism (its host), deriving nutrition from the host, benefiting at the expense of its host.
Order
Taxonomic group used in classification of living organisms. Contains similar families.
Ileum
The second, longer part of the small intestine.
Prostaglandin
A chemical made in the body that is involved in inflammatory reactions.
Pericycle
A layer of cells in the root that lies just inside the endodermis. It usually consists of meristematic cells whose division gives rise to lateral roots.
Optimum (temperature / pH)
The condition that gives the fastest rate of reaction in enzyme-controlled reactions.
Multinucleate
Describes cytoplasm that is not divided into cells but contains many nuclei.