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.
A specialised area adapted to make it easier for molecules to cross from one side of the surface to the other.
Sex cells, usually haploid (one set of chromosomes). Fuse during sexual reproduction to form zygotes (diploid).
The covalent bond formed when carbohydrate molecules are joined together in condensation reactions.
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.
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.
Type of protein associated with DNA in eukaryotes. DNA is wound around them to form chromatin.
Chemicals made in endocrine glands that are carried in the blood to target cells/tissues/organs. They act as chemical messengers.
A chain of carbon atoms bonded together with hydrogen atoms bonded onto the carbons.
Ability of the immune system to respond very quickly to antigens that it recognises as they have entered the body before.
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.
A group of factors with non-specific antiviral activity. They also affect the immune system.
The simple theory of enzyme action where the active site is directly complementary to the substrate molecule.
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.
Membrane-bound vesicles made by pinching off from the Golgi body. They usually contain digestive enzymes.
Large, phagocytic, amoeba-like white blood cells that engulf, ingest and destroy bacteria, damaged cells and worn-out red blood cells.
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.
Proteins associated with microtubules. The proteins can move along microtubules. Kinesin moves towards the (+) end of the microtubules and dynein moves towards the (-) end.
Nuclear division that results in the formation of cells that are genetically identical to the parent cell.
The proportion of people in a population who are ill with a particular disease at any one time.
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.
The mechanism for evolution in which the best-adapted organisms in a population can outcompete those that are less well-adapted.
The exact role of an organism in the ecosystem - its use of the living and non-living components of the ecosystem.
An inhibitor of an enzyme-controlled reaction that binds to the enzyme molecule in a region away from the active site.
A large, membrane-bound organelle found in eukaryotic cells, which contains the genetic material in the form of chromosomes.
The total substances taken into an animal or plant for use in metabolism (the sum total of its diet).
Infection caused by an organism that infects a host with a weakened (compromised) immune system.
A collection of tissues that work together to perform a specific overall function or set of functions within a multicellular organism.
Structure inside a cell. Each has a specific function and many are surrounded by membrane.
Nitrogenous coompound in nucleic acid: adenine, thymine, uracil, cytosine, guanine are examples.
The amount of oxygen in the air expressed as the pressure created by the presence of oxygen, expressed in kilopascals (kPa).
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.
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.
Immunity acquired indirectly without activation of the lymphocytes, such as through the placenta, from breast milk, or by injection.
A molecule consisting of a small number of amino acids bonded together by (covalent) peptide bonds.
The covalent bond formed when amino acids are joined together in condensation reactions.
Gives measure of acidity/alkalinity of a solution. It is the reciprocal of the logarithmic value of the hydrogen ion concentration.
A cell that can carry out phagocytosis and ingest bacteria or small particles. Macrophages and neutrophils are phagocytes.
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.
A molecule consisting of a glycerol molecule, two fatty acid molecules and a phosphate group covalently bonded together. Forms the basis of cell membranes.
Process by which plants, some bacteria and some protoctists make food using carbon dioxide, water and sunlight energy.
Pits (or bordered pits)
Thin areas in the lignified walls of xylem tissue cells that allow communication between adjacent cells.
Proteins made in the liver that are found in the non-cellular fraction of the blood.
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.
A fine strand of cytoplasm that links the protoplasm of adjacent cells through a thin area of cell wall called a pit.
Detachment of the plasma membrane from the cell wall as the cytoplasm shrinks when water is lost from a plant cell.
Stem cells capable of differentiating to become a limited number of cell types found in the organism (e.g. cells of an early embryo).
A large molecule made up of many/repeating similar, smaller molecules (monomers) covalently bonded together.
A polymer consisting of many nucleotide monomers covalently bonded together (DNA and RNA are examples).
Apparatus used to measure water uptake in a leafy shoot and so to estimate rate of transpiration.
The phase of mitosis where the chromosomes become visible as a pair of sister chromatids joined at the centromere.
A non-protein organic molecule that forms a permanent part of a functioning protein molecule.
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.
A study is that does not involve quantity (numbers). For example, simple observations to see if a particular species lives in a selected area.
A study involving quantity (numbers). For example, if you count the number of individuals of a species in a selected area.
Protein structure where a protein consists of more than one polypeptide chain e.g. Haemoglobin and insulin.
Protein or glycoprotein molecules on cell surfaces, used for attachment of specific substances such as hormones or viruses.
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.
The process in which energy is released from complex molecules, such as glucose, within cells and transferred to molecules of ATP.
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.
Defences that attempt to kill or inactivate pathogens that have already invaded the body.
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.
The replication of a DNA strand where the replicated double helix consists of one old strand and one newly synthesised strand.
Valves between the ventricles and the main arteries leading out of the heart, which prevent backflow of blood.
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.
Single circulatory system
A circulation in which blood flows through the heart once during each circulation of the body.
Sinoatrial node (SAN)
The patch of tissue that initiates the heartbeat by sending waves of excitation over the atria.
A type of muscle (involuntary muscle) found mostly in certain internal organs and involved in involuntary movements such as peristalsis.
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.
A group of organisms whose members are similar to each other in shape, physiology, biochemistry and behaviour, and can interbreed to produce fertile offspring.
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.
A polysaccharide found in plant cells. It is formed from the covalent bonding together of many glucose molecules.
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.
The gel-like matrix found in chloroplasts. The membranes of the thylakoids/grana are embedded in it.
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.
The 'skin' on the surface of water formed as a result of hydrogen bonding in water molecules pulling the surface molecules downwards.
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.
Speciation that occurs within one area - some factor other than geographical separation has prevented free interbreeding between members of the species.
The circulation that carries blood around the body, excluding the circulation to the lungs.
String-like tendons used to attach the atrioventricular valves of the heart to the sides of the ventricle wall. Sometimes called heart strings.
The overall three-dimensional shape of a protein molecule. Involves hydrogen bonding, disulfide bridges, ionic bonds and hydrophobic interactions.
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.
Undifferentiated cell that is capable of differentiating into any kind of specialised cell.
The assembly of an mRNA molecule that is a copy of the DNA coding strand (and complementary to the template strand).
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.
Organism that has genetic material from another organism, usually by genetic engineering.
A molecule consisting of a glycerol molecule and three fatty acid molecules covalently bonded together.
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.
The detailed structure of the internal components of cells as revealed by the electron microscope rather than by the light microscope.
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.
The pathway taken by water in plants as it passes from cell to cell via the cell cytoplasm and vacuole.
Condition in an experimental investigation. Can be independent (altered by the experimenter) or dependent (respond to changes in the independent variable).
Vascular tissue / bundle
The transport tissue in a plant - usually found as a bundle containing both xylem and phloem.
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.
Breathing - movement of diaphragm and rib cage that bring air into and out of the lungs.
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.
A plant tissue containing vessels (and other cells) that are used to transport water in a plant and provide support.
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.
A protein secondary structure - a right-handed spiral held in place by hydrogen bonds between adjacent C=O and NH groups.
Speciation due to organisms of a species being separated by geographical barriers so that eventually they become so different that they cannot interbreed.
An organic compound that contains both an amino group(-NH2) and a carboxyl group (-COOH). The monomers of protein molecules.
Movement of substances across membranes against their concentration gradient, requiring the use of energy in the form of ATP.
A macrophage that has ingested a pathogen and displays some of the pathogen's molecules on its cell surface membrane.
Part of a starch molecule, consisting of many thousands of glucose residues bonded together.
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.
The use of comparative studies or samples to determine the concentration or quantity of a substance in a sample.
A nitrogen-containing organic base found in nucleic acids. It pairs with thymine in DNA and with uracil in RNA.
An organism that makes its own food from simple inorganic molecules, such as carbon dioxide and water.
Protein molecules released by the immune system in response to an antigen, which are capable of neutralising the effects of the antigen.
The production of genetically identical new organisms by a single 'parent' organism.
Rules governing the complementary bases in nucleic acids. Adenine pairs with thymine (or uracil). Guanine pairs with cytosine.
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.
Hardening of the artery walls and loss of elasticity caused by atherosclerosis or by deposition of calcium.
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).
A protein found in membranes, which is capable of carrying a specific molecule or ion through the membrane by active transport.
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.
The region of a chromosome where two sister chromatids are joined together, and where the spindle fibre attaches during cell division.
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.
Material staining dark red in the nucleus during interphase. It consists of nucleic acids and proteins. Condenses into chromosomes during prophase of nucler division.
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.
Describes a result/data point that does not appear to fit the pattern of the other results.
The movement of chloride ions into red blood cells to balance the loss of hydrogencarbonate ions.
Feature of a living organism that increases its chances of survival, for example thick fur on an animal that lives in a cold habitat.
A foreign molecule (which may be protein or glycoprotein) that can provoke an immune response.
Also called selective breeding - the process of improving a variety of crop plant or domesticated animal by breeding from individuals with desired characteristics.
In mitosis, the stage when the newly separated chromatids are pulled towards opposite poles of the nuclear spindle.
Hormone-like proteins produced by vertebrates, which are used for communication between cells, allowing some cells to regulate the activities of others.
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.
A lipid molecule (not a triglyceride) found in all cell membranes and involved in the synthesis of steroid hormones.
A strip of waterproof material (suberin) in the cell walls of root endodermis cells. It blocks the apoplast pathway.
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.
The selection of cells (of the immune system) with a specific receptor site. These cells will undergo expansion as part of the immune response.
A linear DNA molecule wrapped around histone proteins found in the nucleus. Become visible in prophase of cell division.
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.
A substance that increases the rate of a reaction but does not take part in the reaction, and so is re-usable.
The folds found in the inner membrane of a mitochondrion. Stalked particles containing ATP synthase are found here.
A system of naming living things using two Latin words - the genus name and the specific name.
Variation where there is a range of intermediates, such as height, hair colour and intelligence in humans. Affected by multiple genes and environment
Trace (graph) showing the electrical activity of the heart muscle (atria and ventricles) during a cycle.
Classification level introduced by Carl Woese dividing the kingdom Prokaryotae into two and placing all Eukaryotes into a third.
A type of tissue that consists of separate cells held together by a ground substance (matrix).
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.
Bohr shift / Bohr effect
The effect of carbon dioxide concentration on the affinity of haemoglobin for oxygen.
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.
Molecules produced by microorganisms that kill or limit the growth of other microorganisms
Method of cell division in bacteria. The DNA replicates and the cell divides into two, each having the same DNA as the parent cell.
The number and variety of living things to be found in the world, in an ecosystem or in a habitat.
A class of biological molecules with the general formula Cx(H2O)y. It includes sugars, starches, glycogen and cellulose.
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.
A replicated chromosome appears as two strands in early stages of cell division. Each strand is called a.....
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.
Refers to structures that fit together because their shapes and/or charges match up. For example, adenine and cytosine in DNA.
Taxonomic group used in classification of living organisms. Below phyla but containing orders (consisting of families, genera and species).
A cell in the phloem involved in actively loading sucrose into the sieve tube elements, to which it is linked by many plasmodesmata.
Part of an experimental investigation - set up to show that the variable being investigated is responsible for the change observed.
A sheet of muscular and fibrous tissue separating the chest cavity from the abdominal cavity.
Processes that lead to communication and coordination between cells. Hormones binding to their receptors on the cell surface membrane are an example.
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.
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.
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.
A suspension of one material in another as droplets, because it does not dissolve. For example, fat droplets dispersed in water.
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.
The intermediate structure formed when a substrate molecule binds to an enzyme molecule.
Process by which the present diversity of living organisms arose from simple primitive organisms, with new species arising by natural selection.
The period when the heart muscle in the ventricles is relaxing and blood pressure is at its lowest.
An organic non-protein molecule that binds temporarily with substrate to an enzyme active site. It is essential for enzyme activity.
An organelle found in plants, which contains chlorophyll and is responsible for photosynthetic activity in the plant.
The organisation of living organisms (or other items) into groups according to their shared similarities.
A structural fibrous protein found in connective tissue, bones, skin and cartilage. It accounts for 30% of body protein.
A substance that reduces the rate of an enzyme-controlled reaction by binding to the enzyme's active site.
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.
A protein pore that spans a membrane, through which very small ions and water soluble molecules may pass.
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.
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.
Describes the structure of DNA, a twisted helix of two strands with bases joining the strands.
The bond formed when fatty acid molecules are joined to glycerol molecules in condensation reactions.
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.
The process of removing materials from the cell by fusing vesicles containing the material with the plasma membrane .
The intermediate structure in which product molecules are bound to an enzyme molecule.
Describes a disease that spreads to many people quickly and affects a large proportion of the population.
A 6-carbon monosaccharide sugar. Very important source of energy within cells. Substrate for glycolysis.
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.
Membrane-bound organelle in eukaryote cells. Involved in the modification and transport of proteins.
Cells that have a nucleus inside a nuclear envelope, and other membrane-bound organelles.
A polysaccharide found in animal cells. Formed from the bonding together of many glucose molecules, used as a store of glucose.
The passive movement of molecules across membranes down their concentration gradient. Aided by transport proteins but no metabolic energy is required.
An irreversible change in the tertiary structure of a protein molecule. It leads to loss of function in most proteins.
An animal that produces heat within its cells, from respiration, to maintain a constant body temperature.
Protein channels found in cell membranes, which can be opened or closed in response to cell signals.
All the living organisms and all the non-living components in a specific area, and their interactions.
Proteins with relatively spherical molecules, soluble in water, often having metabolic roles in organisms.
A 3-carbon (alcohol) molecule. It forms the basis of lipids when fatty acids are bonded to it.
A waterproofing substance that impregnates the walls of xylem tissue. Lignin gives wood its strength.
Fluid mosaic (model)
The model of cell membrane structure proposed by Singer and Nicholson - a phospholipid bilayer with proteins 'floating' in it.
Simple procedures that show the presence of various biological molecules in samples or structures.
Cell-signalling chemicals. Some are involved in activating cells of the immune system. A type of cytokine.
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.
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.
Organism that gains nutrients from complex organic molecules. These molecules are digested by enzymes to simple soluble molecules.
Taxonomic group. Living organisms are grouped into one of five: Prokaryotae, Protoctista, Fungi, Plantae and Animalia.
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.
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.
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.
Nuclear division that results in the formation of cells containing half the number of chromosomes of the adult cell.
B and T cells that remain in the body after an immune response. Their presence enables a much faster and greater second immune response.
A protein with a relatively long, thin structure, which is insoluble in water and metabolically inactive, often having a structural role within the organism.
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.
A group of organisms that share a common ancestor and therefore belong to the same classification group.
Term used to describe a large range of species in an area or a population of organisms that have significant genetic variation.
The movement of water molecules from a region of higher water potential to a region of lower water potential across a partially permeable membrane.
A variable that limits the rate of a process. If it is increased, then the rate of the process will increase.
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.
A length of DNA that carries the code for the synthesis of one (or more) specific polypeptide(s).
The organelle found in cells in which most of the ATP synthesis occurs. It is the site of aerobic respiration.
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.
An organism that lives in or on another living organism (its host), deriving nutrition from the host, benefiting at the expense of its host.
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.