Bio Common Defns

Complied by Mrs Eunice Chan/Oct2012, revised Aug2020 ©The Biology Jotter Book Glossary of key terms for O Level Biology Word Definition Diffusion Net movement of molecules from a region of their higher concentration to a region of their lower concentration, down a concentration gradient Osmosis Movement of water molecules from a region of higher water potential to a region of lower water potential, across a partially permeable membrane Water potential A measure of the tendency of water to move from one place to another Concentration gradient Difference in concentration between two regions Plasmolysis Shrinking of cytoplasm away from the cell wall when the plant cells are immersed in a solution more concentrated than their cell sap Turgor pressure Pressure exerted outwards on the plant cell wall due to the water in the cell, giving the cell its turgidity. Active transport Process in which energy from respiration is used to move molecules against a concentration gradient, from a region of lower concentration to a region of higher concentration Condensation reaction A chemical reaction in which two simple molecules are joined together to form a larger molecule with the removal of one molecule of water Hydrolysis A chemical reaction in which water molecule is needed to break up a complex molecule into smaller molecules Reducing sugars Sugars which can reduce the copper (II) to copper (I) E.g. glucose, maltose, fructose, lactose Saturated fats Fats with straight fatty acid chains and are found mostly in animals Unsaturated fats Fats with bent fatty acid chains and are found mostly in vegetables Emulsion A suspension of small drops of a liquid in another liquid Kwashiorkor Protein-deficiency disease in which children have swollen stomachs and dry, scaly skin Enzymes Biological catalysts made with proteins which alter the rate of chemical reactions without themselves being chemically changed at the end of the reactions Activation energy Energy needed to start a chemical reaction Active site Depression on the surface of an enzyme molecule into which the substrate molecule can fit

Complied by Mrs Eunice Chan/Oct2012, revised Aug2020 ©The Biology Jotter Book Word Definition Optimum temperature Temperature at which enzyme is most active, catalysing the largest number of reactions per second Optimum pH pH value at which enzyme is most active, catalysing the largest number of reactions per second Denaturation Change in the three-dimensional structure of an enzyme or any other soluble protein, caused by heat or extreme pH changes Limiting factor Any factor that directly affects a process if its quantity is changed Peristalsis Rhythmic wave-like contractions of the wall of the gut caused by alternate contractions of the circular and longitudinal muscles in the walls to help push food along the gut Emulsification of fats Occurs when bile break big blobs of fat into smaller fat droplets Egestion Removal of undigested food from the body Deamination Process of removing amino groups from excess amino acids and converted to urea Detoxification Process of converting harmful substances into harmless substances Cirrhosis of the liver Disease where liver cells are destroyed and are replaced with fibrous tissue Photosynthesis Process in which light energy absorbed by chlorophyll is transformed into chemical energy. This chemical energy is used to synthesize carbohydrates from water and carbon dioxide, with oxygen being released during the process. Compensation point Point when rate of photosynthesis is the same as rate of respiration Antigen Protein found on the surface of red blood cells which can be recognised by the immune system Antibody A protein produced by lymphocytes in response to the entry of foreign substances in order to render them harmless Pathogen Disease-causing organism Acclimatisation Occurs when body produces more red blood cells to compensate for a lower concentration of oxygen in the atmosphere Phagocytosis Process of engulfing and ingesting foreign particles by white blood cells/phagocytes Blood serum Blood plasma without fibrin and blood clotting factors

Complied by Mrs Eunice Chan/Oct2012, revised Aug2020 ©The Biology Jotter Book Word Definition Double circulation Consists of pulmonary circulation and systemic circulation where blood passes through the heart twice in one complete circuit Ventricular systole Occurs when ventricles contract Ventricular diastole Occurs when ventricles relax Blood pressure Force that blood exerts on the walls of blood vessels Tissue fluid Blood plasma that has moved out of blood capillaries to the surrounding tissue cells Atherosclerosis Deposition of fatty substances on the inner surface of an artery Thrombosis A blood clot that forms in an artery Translocation Transport of manufactured food substances such as sugars and amino acids in the phloem of plants Root pressure Pressure that forces water, absorbed from soil, to move through the roots and up the stem of a plant. This is normally due to the lower water potential in root cells Transpiration Loss of water vapour from aerial parts of a plant, especially through the stomata of leaves Transpiration stream Stream of water up a plant Wilting Condition which results when plants lose more water through transpiration than is absorbed from roots Respiration Oxidation of food substances with the release of energy in living cells Aerobic respiration Oxidation of food substances in living cells, in the presence of oxygen, with the release a large amount of energy. Carbon dioxide and water are released as waste products. Anaerobic respiration Breakdown of food substances in the absence of oxygen. Less energy is released than aerobic respiration. Oxygen debt Amount of oxygen required to oxidise lactic acid produced in muscles during anaerobic respiration Gaseous exchange Exchange of gases between an organism and the environment Inhalation / inspiration Taking in of air Exhalation / expiration Giving out of air

Complied by Mrs Eunice Chan/Oct2012, revised Aug2020 ©The Biology Jotter Book Word Definition Cancer An uncontrolled division of cells producing outgrowths or lumps of tissues Excretion Process by which metabolic waste products and toxic materials are removed from the body of an organism Ultrafiltration Process in which hydrostatic pressure causes water and small dissolved substances and ions to move across the capillary wall into the nephron tubule Osmoregulation Control of water and solute levels in the blood to maintain a constant water potential in the body Homeostasis Maintenance of a constant internal environment Stimulus A change from the normal condition Receptors Organs in the body that detect changes in body conditions Negative feedback Reverse effect of a stimulus to restore the normal conditions of the internal environment Vasoconstriction Reduction in internal diameter of blood vessels in body to reduce the amount of blood flow Vasodilation Increase in internal diameter of blood vessels in body to increase amount of blood flow Response (to a stimulus) Reaction of an organism to a stimulus Effectors Organs or cells in the body that produce a response when stimulated by a nerve impulse Synapse Junction between two neurones or a junction between a neurone and an effector Nerve impulse Electrochemical signal Neurotransmitters Chemicals which transmit nerve impulses across a synapse Reflex action Immediate response to a specific stimulus without conscious control Voluntary action Action that is controlled by conscious thought Involuntary action Action that is not under the control of will of an individual Reflex arc Shortest pathway by which nerve impulses travel from the receptor to the effector in a reflex action

Complied by Mrs Eunice Chan/Oct2012, revised Aug2020 ©The Biology Jotter Book Word Definition Sense organs Receptors which receive stimuli a