B2 - Organisation

• Specialised cells


  Cells that differentiate and become specialised as an organism develops
• Most types of animal cell differentiate at an early stage, but many types of plant cell can differentiate throughout their life
• Cell differentiation

  As a cell differentiates, it may change shape and different sub-cellular structures develop to enable it to carry out a specific function
• Specialised animal cells


  • Sperm
  • Nerve
  • Muscle
• Specialised plant cells


  • Root hair
  • Xylem
  • Phloem
• Sperm cell

  • Tail to propel the sperm to fertilise the egg
  • Mitochondria to provide energy for their journey
  • Nucleus with only one set of genetic material
  • Acrosome containing enzymes to allow the sperm to penetrate the outer layer of the egg
• Xylem cells

  • Arranged end to end but the end walls break down to form hollow tubes
  • Cell wall strengthened by lignin
• Tissue

  A group of cells with a similar structure and function, which all work together to do a job
• Organ


  Groups of different tissues, which all work together to perform a specific job
• Organ system


  Groups of organs working together to do a particular job
• Enzyme

  Biological catalysts that speed up chemical reactions in living organisms
• Enzymes

  • They are all large proteins
  • They have an active site within the protein molecule
  • Each enzyme catalyses a specific reaction
  • They work best at a specific temperature and pH called the optimum
• Lock and key theory


  The chemical that reacts (substrate) fits into the enzyme's active site (lock)
• High temperature and extremes of pH make enzymes change shape (denaturing), so the enzyme cannot work once it has been denatured
• Digestive enzymes


  Enzymes produced by specialised cells in glands and in the gut lining that catalyse the breakdown of large insoluble food molecules into smaller soluble molecules
• Digestive enzymes

  • Carbohydrase
  • Protease
  • Lipase
• Amylase


  A carbohydrase enzyme that breaks down starch into sugar (maltose)
• Protease


  An enzyme that breaks down proteins into amino acids
• Lipase


  An enzyme that breaks down lipids into fatty acids and glycerol
• Blood

  A liquid called plasma with three different components suspended in it: red blood cells, white blood cells, and platelets
• Red blood cells


  • Contain haemoglobin to transport oxygen
  • Do not contain a nucleus, so there is more room for haemoglobin
  • Are very small to fit through capillaries
  • Are shaped like biconcave discs for a large surface area
• White blood cells

  • Help to protect the body against infection
  • Can change shape to squeeze out of blood vessels into tissues or surround and engulf microorganisms
• Platelets


  Fragments of cells that collect at wounds and trigger blood clotting
• Heart


  Pumps blood around the body in a double circulatory system, with blood passing through the heart twice on each circuit
• Heart chambers

  • Left and right atria receive blood from veins
  • Left and right ventricles pump blood out into arteries
• Pacemaker


  A group of cells in the right atrium that control the natural resting heart rate
• Artificial pacemaker


  An electrical device used to correct irregularities in the heart rate
• Communicable disease


  A disease that can be spread between organisms
• Non-communicable disease


  A disease that cannot be spread between organisms
• Risk factor


  An aspect of a person's lifestyle or substance in their body/environment that makes it more likely they will develop a disease
• Risk factors(CHD)


  • Lack of exercise
  • Chemicals from smoking
• Coronary heart disease


  A condition where layers of fatty material build up inside the coronary arteries and narrow them
• Stent


  A device used to keep coronary arteries open
• Statins


  Drugs that reduce blood cholesterol levels and slow down the rate at which fatty materials build up
• Heart valve replacement


  Replacement of faulty heart valves that have developed a leak or do not open fully
• Heart transplant


  Transplantation of a donor heart or heart and lungs to treat heart failure
• Artificial heart


  A device used to keep patients alive while waiting for a heart transplant or to allow the heart to recover
• Cancer


  A disease caused by uncontrolled cell division that can form masses of cells called tumours
• Benign tumour


  A tumour that does not spread around the body
• Malignant tumour


  A tumour that spreads, in the blood, to different parts of the body where it forms secondary tumours