Organisms

• Levels of organisation


  • Cell
  • Tissue
  • Organ
  • Organ system
  • Organism
• Tissue


  • Single group of cells
• Organ


  • Group of tissues working together to perform a function
• Organ system


  • Group of organs working together to keep the body alive
• Organ systems


  • Skeletal
  • Respiratory
  • Reproductive
  • Digestive
  • Circulatory
• Digestive system function


  1. Mouth/teeth physically break down food

  2. Saliva glands produce enzymes

  3. Food travels to stomach

  4. Food churned in stomach

  5. Food travels to small intestine where it is digested by enzymes and absorbed into bloodstream

  6. Water passes back into body from large intestine, leaving solid waste
• You'll soon know how to investigate the effect of pH on the rate of enzyme activity
• The enzyme smyle catalyses the breakdown of starch to maltose
• If starch is present, the iodine solution will change from browny-orange to blue-black
• Investigating how pH affects amylase activity

  1. Put a drop of iodine solution into every well of a spotting file

  2. Place Bunsen burner on a heat-proof mat, and a tripod and gauze over the Bunsen burner. Put a beaker of water on top of the tripod and heat the water until it is 35 C

  3. Use a syringe to add 1 cm³ of amylase solution and 1 cm³ of a buffer solution with a pH of 5 to a boiling tube

  4. Use a different syringe to add 5 cm³ of a starch solution to the boiling tube

  5. Immediately mix the contents of the boiling tube and start a stop clock

  6. Use continuous sampling to record how long it takes for the amylase to break down all of the starch

  7. Repeat the whole experiment with buffer solutions of different pH values
• Remember to control any variables such as time (eg. concentration and volume of amylase solution) to make it a fair test
• Rate of reaction


  A measure of how much something changes over time
• Calculating the rate of reaction


  Amount of product formed / Time taken
• The enzyme catalase catalyses the breakdown of hydrogen peroxide into water and oxygen
• Parts of the thorax


  • Esophagus (food pipe)
  • Lungs
  • Pleural membranes
  • Trachea
  • Bronchi
  • Bronchioles
  • Alveoli
• Alveoli


  • Millions and millions of little air sacs where gas exchange takes place
  • Surrounded by a network of blood capillaries
• Gas exchange in the alveoli


  1. Oxygen diffuses out of the alveolus (high concentration) into the blood (low concentration)

  2. Carbon dioxide diffuses out of the blood (high concentration) into the alveolus (low concentration) to be breathed out

  3. Oxygen is released from the red blood cells (high concentration) and diffuses into the body cells (low concentration)

  4. Carbon dioxide diffuses out of the body cells (high concentration) into the blood (low concentration)
• Calculating breathing rate


  Breaths per minute = Number of breaths / Number of minutes