Organisation

• Cells are the basic building blocks of all living organisms
• Tissue


  A group of cells with similar structure and function
• Organ


  A group of tissues performing specific functions
• Organ system


  A group of organs performing a specific function
• Organism


  A group of organ systems together
• Enzymes


  Protein molecules found in cells that speed up reactions in the body
• Enzymes


  • They can be reused as their shape remains unchanged
  • They depend on their shape to work
• Lock and key model

  Explains how enzymes work - the substrate molecule fits into the active site of the enzyme
• Enzymes control metabolism in the body - reactions that build up and break down molecules
• Measuring enzyme-controlled reactions


  • Volume of gas produced per time
  • Time taken for colour change
  • Time taken for pH change
• As temperature increases


  The rate of enzyme-controlled reactions increases
• At high temperatures


  Enzymes denature and the active site changes shape
• At optimum pH


  Enzymes work at their highest rate
• Parts of the digestive system

  • Mouth
  • Esophagus
  • Stomach
  • Pancreas
  • Small intestine
  • Large intestine
  • Rectum
  • Anus
  • Liver
  • Gallbladder
• Function of the digestive system

  To digest large insoluble food molecules into more soluble molecules that can be absorbed into the blood
• Key digestive enzymes


  • Carbohydrase
  • Lipase
  • Amylase
  • Protease
• Location of digestive enzymes

  • Mouth produces amylase
  • Stomach produces protease
  • Pancreas and small intestine produce all 4 enzymes
• Carbohydrase enzymes


  Break down carbohydrates into simple sugars
• Amylase


  A type of carbohydrase that breaks down starch
• Protease enzymes


  Break down proteins into amino acids
• Lipase enzymes


  Break down lipids (fats) into glycerol and fatty acids
• Bile


  Produced by the liver, helps digest lipids by emulsifying them and neutralizing stomach acid
• Iodine test for starch

  Iodine solution turns blue-black in the presence of starch
• Biuret test for protein


  Biuret solution turns lilac in the presence of protein
• Ethanol and water test for lipids


  Forms a cloudy white emulsion in the presence of lipids
• Benedict's test for sugars

  Benedict's reagent turns brick red when heated in the presence of sugars
• Double circulatory system


  Blood is pumped to the body by the left side of the heart and to the lungs by the right side
• Structure of arteries


  Narrow lumen, thick muscle layer to contract, thick elastic tissue layer to maintain pressure
• Structure of capillaries


  Very thin walls, only one cell thick, to allow short diffusion distance
• Lumen


  The part inside where the blood is carried
• Arteries


  • Narrow lumen
  • Thick layer of muscle around the artery that can contract to pump blood
  • Thick elastic tissue layer that recoils and maintains pressure
• Capillaries


  The smallest blood vessels
• Capillaries


  • Very thin walls, only one cell thick
  • Allow for short diffusion distance for gas exchange
  • Very narrow, so red blood cells travel in single line
  • Many capillaries provide large surface area for gas exchange
• Veins


  • Larger lumen compared to arteries
  • Thinner walls made of elastic and muscle tissue
  • Have valves to prevent backflow of blood
• Components of blood


  • Plasma
  • White blood cells
  • Red blood cells
  • Platelets
• Plasma


  The liquid part of blood that transports dissolved substances
• Red blood cells


  Contain hemoglobin which carries oxygen, have a biconcave shape to increase surface area
• Platelets


  Small cell fragments that help blood to clot
• Blood is considered a tissue, made of plasma in which red and white blood cells and platelets are suspended
• Coronary arteries


  Blood vessels that supply the heart muscle with oxygen and glucose