B2 Organisation

• Tissue


  One type of cell carrying out one function
• Organ


  Made up from lots of different types of cells carrying out a joint function
• Organ system


  A group of organs that work together to carry out a function
• Hierarchy of biological organisation

  • Cells
  • Tissues
  • Organs
  • Organ systems
• Digestive system


  1. Mouth mechanically breaks down food

  2. Saliva glands produce enzymes

  3. Liver produces bile

  4. Small intestine absorbs nutrients

  5. Stomach churns food
• Digestive enzymes


  • Lipase
  • Protease
  • Amylase
• Enzyme mechanism


  • Enzyme has a specifically shaped active site
  • Substrate binds to active site
  • Enzyme-substrate complex forms
  • Enzyme catalyses reaction
  • Products are released
• Temperature increases


  Enzyme activity increases to an optimal point, then decreases as enzyme is denatured
• pH changes


  Enzyme activity decreases as pH moves away from optimal
• Respiratory system


  1. Air enters through mouth/nose

  2. Travels down trachea

  3. Into bronchi

  4. Into bronchioles

  5. Into alveoli for gas exchange
• Respiratory system


  • Diaphragm moves to bring air in and out
  • Intercostal muscles allow rib cage expansion
• Cardiovascular system


  1. Blood pumped from heart to lungs

  2. Blood returns to heart

  3. Blood pumped around body
• Heart structure


  • Right side pumps blood to lungs, left side pumps blood around body
  • Valves only allow one-way flow of blood
• Blood components


  • Red blood cells
  • White blood cells
  • Platelets
  • Plasma
• Cardiovascular disease


  • Fatty deposits build up in coronary arteries
  • Blood clots form and block arteries
  • Lack of oxygen causes cell death
  • Heart attack can occur
• Health


  • Overall state of physical and mental well-being
  • Affected by diet, exercise, community, genes
• Epidemiology


  • Studies levels of health and illness in a population
  • Identifies risk factors
• Cancer


  • Cells divide uncontrollably
  • Benign tumours are slow-growing and harmless
  • Malignant tumours are fast-growing and aggressive
• Cancer risk factors


  • Smoking
  • Diet
  • Sun exposure
  • Unprotected sex
• Leaf structure


  1. Palisade mesophyll for photosynthesis

  2. Spongy mesophyll for gas exchange

  3. Guard cells and stomata for transpiration

  4. Xylem transports water upwards

  5. Phloem transports nutrients downwards
• Factors affecting transpiration


  • Bright light increases transpiration
  • High temperature increases transpiration
  • High wind increases transpiration
  • High humidity decreases transpiration