Organisation

• Large Multicelular Organisms are Made Up of Cells
• Similar Cells are Organised into Tissues
• Tissues


  A group of cells that work together to carry out a particular function
• Examples of tissues


  • Epidermis, which contains cells to protect whatever is inside
  • Muscle tissue, which makes and secretes chemicals like hormones
  • Nervous tissue, which transmits electrical signals to different parts of the body
• Tissues are Organised into Organs
• Organs are Organised into Organ Systems
• Organ Systems


  • Digestive system
  • Circulatory system
  • Respiratory system
  • Nervous system
• Cells, tissues, organs, organ systems all come together to form a whole organism
• Enzymes


  Catalysts produced by living things
• Enzymes


  • They need the right temperature to work
  • They have special shapes so they can catalyse reactions
• Active site


  The part of the enzyme where the substrate binds and the reaction is catalysed
• Enzymes speed up chemical reactions
• Most enzymes catalyse just one reaction
• The optimum temperature for most enzymes is around normal body temperature
• Enzymes in the small intestine work best at a higher pH
• Investigating the effect of pH on enzyme activity

  1. Prepare enzyme solution

  2. Add buffer solutions at different pH values

  3. Measure the rate of reaction for each pH
• Rate of reaction


  The amount of product formed divided by the time taken
• Digestive enzymes break down large molecules into smaller ones
• Digestive enzymes


  • Carbohydrases convert carbohydrates into simple sugars
  • Proteases convert proteins into amino acids
  • Lipases convert lipids into glycerol and fatty acids
• Bile


  Neutralises stomach acid and emulsifies fats
• The breakdown of food is catalysed by enzymes
• Organs involved in digestion

  • Salivary glands
  • Stomach
  • Pancreas
  • Small intestine
  • Large intestine
• Food tests can be used to detect the presence of different nutrients in food
• Benedict's test for sugars


  1. Add food sample to Benedict's solution

  2. Heat in water bath

  3. Observe colour change
• Iodine test for starch

  1. Add iodine solution to food sample

  2. Observe colour change
• Biuret test for proteins

  1. Add Biuret solution to food sample

  2. Observe colour change
• Sudan III test for lipids


  1. Add Sudan III stain to food sample

  2. Observe separation into layers
• The lungs are located in the thorax
• The alveoli in the lungs carry out gas exchange
• The heart has a double circulatory system
• Calculating breathing rate


  1. Count the number of breaths in a set time period

  2. Divide the number of breaths by the time to get breaths per minute
• The heart contracts to pump blood around the body
• Pacemaker


  Group of cells in the right atrium that control the heartbeat
• Artificial pacemakers can be implanted to regulate the heartbeat
• Blood vessels


  • Arteries carry blood under pressure away from the heart
  • Capillaries are very small to allow exchange
  • Veins carry blood back to the heart at lower pressure
• Calculating rate of blood flow

  1. Measure volume of blood

  2. Divide by time taken
• Components of blood


  • Red blood cells carry oxygen
  • White blood cells defend against infection
  • Platelets help blood clot
  • Plasma carries dissolved substances
• Coronary heart disease is a type of cardiovascular disease
• Stents can be used to keep arteries open in coronary heart disease
• Artificial hearts can be used to pump blood in people whose own heart has failed