Biology: Organisation: Key terms

• Specialised


  adapted for a particular purpose
• Tissue


  a group of cells that have a similar structure and function
• Organ


  a group of tissues gathered together to perform a particular function
• Organ system


  a group of organs that all perform related functions
• Catalyst


  a substance that increases the rate of a chemical reaction without being changed or used itself
• Active site

  area on an enzyme (lock) that a substrate molecule (key) can fit into
• Optimum

  the conditions at which an enzyme works best
• Lock and key theory


  a model used to explain how enzymes work, where the active site is the lock and the substrate is the key
• Denature

  when the shape of an enzyme is changed (by excessive temperature or pH) so that it no longer functions
• Protease


  an enzyme used to break down proteins into amino acids
• Lipase


  an enzyme that breaks down fat into fatty acids and glycerol
• Carbohydrase


  an enzyme that can break down a carbohydrate
• Amylase


  an enzyme that breaks down starch
• Bile


  a fluid, produced by the liver and stored in the gall bladder that emulsifies fat
• Plasma


  the clear fluid part of blood that contains various dissolved substances, such as proteins and mineral ions
• Haemoglobin

  the red pigment in red blood cells, that carries oxygen to the organs
• Double circulatory system


  the type of blood system found in mammals, where the blood goes through the heart twice on each circuit of the body
• Atria

  the upper chambers of the heart
• Ventricles


  the lower two chambers of the heart
• Pacemaker


  a natural or artificial device that controls heart rate
• Pulmonary artery


  the blood vessel carrying deoxygenated blood from the heart to the lungs
• Trachea


  the main tube or windpipe taking air from the mouth down to the lungs
• Bronchi


  the two tubes formed when the trachea divides into two; one passes to each lung
• Bronchioles


  the fine tubes in the lungs that end in alveoli
• Alveoli


  air sacs in the lungs; oxygen diffuses out of them and carbon dioxide diffuses into them
• Pulmonary vein


  the blood vessel carrying oxygenated blood from the lungs to the heart
• Health


  the absence of disease and a state of complete physical, mental and social well-being
• Disease


  a malfunction / infection of the body
• Communicable


  refers to a disease that can be passed on from one person to another
• Non-communicable


  refers to a disease that cannot be passed on from one individual to another
• Risk factor


  a factor that will increase the chance of developing a disease
• Causal mechanism


  a factor that makes a disease more likely to occur and the reason for this effect is known
• Coronary heart disease


  a condition caused by a build-up of fatty deposits in the coronary arteries leading to a lack of blood and oxygen to the heart muscle
• Stent


  a tube that is inserted into a blood vessel to keep it open
• Statins


  a drug used to help lower cholesterol levels in the blood
• Tumours


  groups of cancerous cells
• Benign


  a tumour that will not spread to other parts of the body
• Malignant


  a tumour that can spread to other areas of the body
• Stomata

  openings / pores in the leaves of plants
• Transpiration


  the movement of water through a plant from root to leaf