Biowords 2/3

Question	Answer
Histone	Type of protein associated with DNA in eukaryotes. DNA is wound around histone proteins to form chromatin.
Homologous	Chromosomes that have the same genes at the same loci. Members of an homologous pair of chromosomes pair up during meiosis. Diploid organisms produced by sexual reproduction have homologous pairs of chromosomes one member of each pair from the male parent and the other member from the female parent. (Can also be used to refer to structures that have different functions but have a common evolutionary origin such as human arm and a bird wing.)
Hormone	Chemicals made in endocrine glands that are carried in the blood to target cells/tissues/organs. They act as chemical messengers and are associated with developmental changes of the organism. Most are polypeptides but some are steroids.
Hydrocarbon chain	A chain of carbon atoms bonded together with hydrogen atoms bonded onto the carbons.
Hydrogen bond	A weak bond formed when partially positively charged groups come close to partially negatively charged groups. It is seen in water molecules and 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.
Hydrophilic	Associating with water molecules easily (water-loving).
Hydrophobic	Water-repelling (water-hating).
Hydrostatic pressure	Pressure created by a fluid pushing against the sides of a container.
Hyphae	The strands that make up the body of a fungus.
Ileum	The second longer part of the small intestine.
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.
Inhibition/inhibitor	The slowing of an enzyme-controlled reaction. An inhibitor slows down or prevents the formation of enzymesubstrate complexes.
Initial reaction rate	Rate of reaction at the beginning of the reaction.
Intercostal muscles	Muscles between the ribs responsible for moving the rib cage during breathing.
Interferon	A group of factors with non-specific antiviral activity. They also affect the immune system.
Interleukin	Cell-signalling chemicals. Some are involved in activating cells of the immune system.
Interphase	The phase of the cell cycle where synthesis of new DNA and organelles takes place.
Intracellular (enzymes / digestion)	Inside the cell (intracellular enyzmes/digestion are found 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.
Keratinocytes	Cells that make keratin.
Kinetic energy	Energy of movement.
Kingdom	Taxonomic group. Living organisms are grouped into one of five kingdoms: Prokaryotae Protoctista Fungi Plantae and Animalia.
Lactate	A compound containing lactic acid the product of anaerobic respiration in mammals and some bacteria.
Lacteal	A blind-ending branch of the lymph system found in each villus of the small intestine.
Leucocytes	White blood cells.
Lignin	A waterproofing substance that impregnates the walls of xylem tissue. Lignin gives wood its strength.
Limiting factor	A variable that limits the rate of a process. If it is increased then the rate of the process will increase.
Lipase	An enzyme that catalyses the breakdown of lipid molecules.
Lipids	A diverse group of chemicals that includes triglycerides fatty acids and cholesterol.
Lock-and-key hypothesis	The theory of enzyme action where the enzyme active site is complementary to the substrate molecule like a lock and a key.
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.
Lymphatic system	A system of lymph nodes and lacteals with lymph fluid.
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.
Macromolecule	A very large molecule.
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.
Maltose	A disaccharide molecule consisting of two -glucose molecules bonded together.
Marker-assisted selection	A mechanism used by animal and plant breeders to help select individuals with the desired genotype. The desired gene is linked (marked) to a section of DNA that is easy to identify in a young individual.
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.
Meristem cells	Undifferentiated plant cells capable of rapid cell division.
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.
Metabolism	All the chemical reactions that take place in an organism.
Metaphase	The phase of mitosis where the chromosomes line up at the equator of the spindle.
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.
Microtubules	Components of the cell cytoskeleton. They have a diameter of about 24nm and length varying from several micrometres in most cells to possibly several millimetres in some nerve cells. Microtubules are involved in mitosis cytokinesis and movement of vesicles within cells.
Microvilli	Folds in the membrane of a cell that increase its surface area.
Mitochondrion (pl: mitochondria)	The organelle found in cells in which most of the ATP synthesis occurs. It is the site of aerobic respiration.
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.
Monocytes	Large phagocytic white blood cell.
Monokines	Chemical produced by monocytes to signal to other cells. Also called lymphokines.
Monomer	A small molecule that is one of the units bonded together to form a polymer.
Monophyletic	A group of organisms is said to be monophyletic if they all share a common ancestor and therefore belong to the same classification group.
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 (proteins bonded to carbohydrates) and is used to protect and/or lubricate the surface on to which it is secreted.
Multinucleate	Describes cytoplasm that is not divided into cells but contains many nuclei.
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.
Myogenic	Describes muscle tissue (heart muscle) that generates its own contractions.
Myoglobin	A respiratory pigment (protein) with a higher affinity for oxygen than haemoglobin.
Natural immunity	Immunity acquired through exposure to disease during the normal course of life.
Natural selection	The best-adapted organisms in a population can outcompete those that are less well-adapted. They are selected by the environment to survive and reproduce so passing on the favourable alleles that have made them well-adapted. Over time this produces a change in the proportions of alleles in the gene pool and evolution occurs. Natural selection is the mechanism for evolution.
Neutrophils	Phagocytic white blood cells. They engulf and digest bacteria. Neutrophils have a many-lobed nucleus and a granular cytoplasm due to the large numbers of lysosomes present.
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.
Nucleic acid	A polymer of nucleotide molecules.
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.
Omnipotent	See totipotent.
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.
Optimum (temperature / pH)	The condition that gives the fastest rate of reaction in enzyme-controlled reactions.
Order	Taxonomic group used in classification of living organisms. Similar families are placed in the same order.
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 organelle has a specific function.
Organic base	Nitrogenous base in nucleic acid: adenine thymine uracil cytosine guanine.
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.
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.
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.
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 without activation of the lymphocytes. It is provided by antibodies that have not been manufactured by stimulating the immune system such as through the placenta or 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.
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.
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. So pH 16 are acidic (lots of hydrogen ions) 7 is neutral and 814 are alkaline.
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 the phagosome.
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. Phospholipids form 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. Similar classes are grouped into the same phylum.
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 -lymphocytes (white blood cells) that secrete a specific kind of antibody.
Plasma membrane / cell surface membrane	The membrane that surrounds every cell forming the selectively permeable boundary between the cell and its environment. It is made up of a double layer of phospholipids with embedded proteins.
Plasma proteins	Proteins made in the liver that are found in blood plasma.
Plasmid	Small circular piece of DNA present in some bacterial cells. Plasmids may have genes for antibiotic resistance. Plasmids can also be used as vectors in genetic engineering.
Plasmodesma (pl: plasmodesmata)	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). See also Totipotent/Omnipotent.
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 polynucleotides).
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.
Prostaglandin	A chemical made in the body that is involved in inflammatory reactions.
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 qualitative if it does not involve quantity (numbers). For example simple observations to see if a particular species lives in a selected area is qualitative.
Quantitative	A study is quantitative if it involves quantity (numbers). For example if you count the number of individuals of a species in a selected area the study is quantitative.
Quaternary structure	Protein structure where a protein consists of more than one polypeptide chain. Haemoglobin and insulin both have a quaternary structure.
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 Benedicts test because it is able chemically to reduce copper sulfate in solution.
Reduction	Chemical reaction involving transfer of electrons from one reactant to another. The substance that gains electrons is reduced.
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)	RNA found in ribosomes.
Ribosome	The organelle on which proteins are synthesised inside the cell.
Risk factor	A factor that increases the risk or chance that you may develop a particular disease.
RNA	Ribonucleic acid 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 coiling or folding parts of a protein molecule due to the formation of hydrogen bonds formed as the protein is synthesised. The main forms of secondary structure are the -helix and -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 two strands unzip and a new strand is assembled onto each conserved strand according to the complementary base-pairing rules. 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	The production of a new individual formed by the fusing of gametes from two different parent organisms. The offspring have unique combinations of alleles inherited from both parents.
Sieve tube element	A cell found in phloem tissue through which sap containing sucrose is transported. It has very little cytoplasm no nucleus and non-thickened cellulose cell walls with the end walls perforated to form sieve plates through which the sap passes from element to element.
Simple diffusion	The movement of molecules from a region of their higher concentration to a region of their 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 (s)	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 (morphology) 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. Chromosomes become attached to the spindle at their centromeres and spindle fibres 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 (e.g. totipotent pluripotent).
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. Stomata allow gaseous exchange in plants and also allow transpiration.
Stroma	The gel-like matrix found in chloroplasts. The membranes of the thylakoids/grana are embedded in the stroma.
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 (species diversity habitat diversity and ecosystems) and the local people are able to 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. It is the result of interactions between parts of the protein molecule such as hydrogen bonding formation of disulfide bridges ionic bonds and hydrophobic interactions.
Testosterone	Steroid hormone made in the testes.
Thrombus	A blood clot.

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