Organisation

• Digestive enzymes


  Convert food into small soluble molecules that can be absorbed into the bloodstream
• Carbohydrases


  • Break down carbohydrates to simple sugars
  • Amylase is a carbohydrase which breaks down starch
• Proteases


  • Break down proteins to amino acids
• Lipases


  • Break down lipids (fats) to glycerol and fatty acids
• Products of digestion

  1. Used to build new carbohydrates, lipids and proteins

  2. Some glucose is used in respiration
• Bile


  • Made in the liver and stored in the gall bladder
  • Alkaline to neutralise hydrochloric acid from the stomach
  • Emulsifies fat to form small droplets which increases the surface area
  • The alkaline conditions and large surface area increase the rate of fat breakdown by lipase
• Heart

  • An organ that pumps blood around the body in a double circulatory system
  • The right ventricle pumps blood to the lungs where gas exchange takes place
  • The left ventricle pumps blood around the rest of the body
• Natural resting heart rate


  • Controlled by a group of cells located in the right atrium that act as a pacemaker
  • Artificial pacemakers are electrical devices used to correct irregularities in the heart rate
• Coronary heart disease


  • Layers of fatty material build up inside the coronary arteries, narrowing them
  • Reduces the flow of blood through the coronary arteries, resulting in a lack of oxygen for the heart muscle
  • Stents are used to keep the coronary arteries open
  • Statins are widely used to reduce blood cholesterol levels which slows down the rate of fatty material deposit
• Faulty heart valves


  • Heart valves may become faulty, preventing the valve from opening fully, or the heart valve might develop a leak
  • Faulty heart valves can be replaced using biological or mechanical valves
• Heart failure


  • A donor heart, or heart and lungs can be transplanted
  • Artificial hearts are occasionally used to keep patients alive whilst waiting for a heart transplant, or to allow the heart to rest as an aid to recovery
• Health


  The state of physical and mental well-being
• Diseases


  • Both communicable and non-communicable, are major causes of ill health
  • Other factors including diet, stress and life situations may have a profound effect on both physical and mental health
  • Different types of disease may interact
• Defects in the immune system


  • Mean that an individual is more likely to suffer from infectious diseases
• Viruses living in cells

  • Can be the trigger for cancers
• Immune reactions


  • Initially caused by a pathogen can trigger allergies such as skin rashes and asthma
• Severe physical ill health


  • Can lead to depression and other mental illness
• Risk factors


  • Linked to an increased rate of a disease
  • Can be aspects of a person's lifestyle or substances in the person's body or environment
  • A causal mechanism has been proven for some risk factors, but not in others
• Risk factors


  • The effects of diet, smoking and exercise on cardiovascular disease
  • Obesity as a risk factor for Type 2 diabetes
  • The effect of alcohol on the liver and brain function
  • The effect of smoking on lung disease and lung cancer
  • The effects of smoking and alcohol on unborn babies
  • Carcinogens, including ionising radiation, as risk factors in cancer
• Many diseases are caused by the interaction of a number of factors
• Benign tumours


  • Growths of abnormal cells which are contained in one area, usually within a membrane
  • They do not invade other parts of the body
• Malignant tumour cells


  • Cancers
  • They invade neighbouring tissues and spread to different parts of the body in the blood where they form secondary tumours
• Risk factors for cancer

  • Lifestyle risk factors
  • Genetic risk factors
• Cancer is the result of changes in cells that lead to uncontrolled growth and division
• Root hair cells


  • Adapted for the efficient uptake of water by osmosis, and mineral ions by active transport
• Xylem tissue


  • Transports water and mineral ions from the roots to the stems and leaves
  • Composed of hollow tubes strengthened by lignin adapted for the transport of water in the transpiration stream
• Stomata and guard cells


  • Control gas exchange and water loss
• Phloem tissue


  • Transports dissolved sugars from the leaves to the rest of the plant for immediate use or storage
  • The movement of food molecules through phloem tissue is called translocation
  • Composed of tubes of elongated cells
  • Cell sap can move from one phloem cell to the next through pores in the end walls