B2

• Cells


  The basic building blocks of all living organisms
• Tissue


  A group of cells with a similar structure and function
• Organ

  Aggregations of tissues performing specific functions
• Organ system


  Organs organised to work together to form organisms
• The digestive system is an example of an organ system in which several organs work together to digest and absorb food
• Enzymes catalyse specific reactions in living organisms due to the shape of their active site
• Lock and key theory

  A simplified model to explain enzyme action
• Digestive enzymes


  • Carbohydrases (break down carbohydrates to simple sugars)
  • Proteases (break down proteins to amino acids)
  • Lipases (break down lipids (fats) to glycerol and fatty acids)
• The products of digestion are used to build new carbohydrates, lipids and proteins. Some glucose is used in respiration
• Bile


  Made in the liver and stored in the gall bladder. It is alkaline to neutralise hydrochloric acid from the stomach. It also 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
• The heart is 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
• Blood vessels associated with the heart


  • Aorta
  • Vena cava
  • Pulmonary artery
  • Pulmonary vein
  • Coronary arteries
• Components of blood


  • Plasma
  • Red blood cells
  • White blood cells
  • Platelets
• In coronary heart disease layers of fatty material build up inside the coronary arteries, narrowing them. This reduces the flow of blood through the coronary arteries, resulting in a lack of oxygen for the heart muscle
• Treatments for coronary heart disease

  • Stents to keep coronary arteries open
  • Statins to reduce blood cholesterol levels
  • Replacement of faulty heart valves
  • Heart transplants
• Health


  The state of physical and mental well-being
• Factors that can affect health

  • Diseases (communicable and non-communicable)
  • Diet
  • Stress
  • Life situations
• Different types of disease may interact
• Examples of disease interactions

  • Defects in the immune system leading to more infectious diseases
  • Viruses triggering cancers
  • Immune reactions causing allergies
  • Severe physical ill health leading to mental illness
• Risk factors for non-communicable diseases

  • Diet
  • Alcohol
  • Smoking
  • Obesity
  • Carcinogens including ionising radiation
• Obesity


  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


  • Ionising radiation
  • Other carcinogens
• Cancer is the result of changes in cells that lead to uncontrolled growth and division
• 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
• Plant tissues include: epidermal tissues, palisade mesophyll, spongy mesophyll, xylem and phloem, meristem tissue found at the growing tips of shoots and roots
• The leaf is a plant organ. Knowledge limited to epidermis, palisade and spongy mesophyll, xylem and phloem, and guard cells surrounding stomata
• Root hair cells, xylem and phloem


  Adapted to their functions
• Simple compound measures


  Such as the rate of transpiration
• The roots, stem and leaves form a plant organ system for transport of substances around the plant
• Root hair cells are 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. It is composed of hollow tubes strengthened by lignin adapted for the transport of water in the transpiration stream
• The role of stomata and guard cells are to 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
• Phloem is composed of tubes of elongated cells. Cell sap can move from one phloem cell to the next through pores in the end walls