Organisation

• Cells


  Make up all living things
• Tissue


  A group of specialised cells with a similar structure and function, can be made of more than one type of cell
• Organ


  Formed from a number of different tissues, working together to produce a specific function
• Organ system


  Organs organised to work together to perform a certain function
• The digestive system is an organ system, as it is made up of organs working together to perform a certain function
• Organs of the digestive system

  • Glands (salivary glands and pancreas)
  • Stomach
  • Small intestine
  • Liver
  • Gall bladder
  • Large intestine
  • Rectum
  • Anus
• Enzymes


  Biological catalysts, a substance that increases the rate of reaction without being used up
• How enzymes work (Lock and Key Hypothesis)

  1. Substrate shape is complementary to active site shape, forming enzyme-substrate complex

  2. Reaction takes place and products are released
• Enzymes


  • They can both break up large molecules and join small ones
  • They are protein molecules and the shape of the enzyme is vital to its function
• Optimum pH and temperature for enzymes

  • Optimum temperature is around 37 degrees celsius (body temperature)
  • Optimum pH for most enzymes is 7, but some have a low optimum pH
• Types of enzymes


  • Carbohydrases (convert carbohydrates into simple sugars)
  • Proteases (convert proteins into amino acids)
  • Lipases (convert lipids into fatty acids and glycerol)
• Soluble glucose, amino acids, fatty acids and glycerol pass into the bloodstream to be carried to all the cells around the body
• Tests to determine composition of a solution

  • Benedict's test (for sugars)
  • Iodine test (for starch)
  • Biuret test (for protein)
  • Emulsion test (for lipids)
  • Sudan III test (for lipids)
• Bile


  • Produced in the liver and stored in the gallbladder, then released into the small intestine
  • Alkaline to neutralise hydrochloric acid, and emulsifies large fat droplets
• Investigating the effect of pH on an enzyme controlled reaction

  1. Use iodine to detect presence of starch, take samples at regular intervals and record time for starch to be completely broken down

  2. Repeat at different pH values while controlling other factors
• Circulatory system


  Carries oxygen and nutrients to every cell in the body and removes the waste products
• Double circulatory system of the heart

  1. Deoxygenated blood flows into right atrium and right ventricle, which pumps it to the lungs

  2. Oxygenated blood flows into left atrium and left ventricle, which pumps it around the body
• Structure of the heart

  • Muscular walls, 4 chambers, valves, coronary arteries
• Heartbeat process


  Blood flows into atria, atria contract forcing blood into ventricles, ventricles contract pushing blood out
• Natural resting heart rate

  Controlled by pacemaker cells in right atrium providing electrical stimulation
• Artificial pacemaker


  Electrical device that produces a signal causing the heart to beat at a normal speed
• Types of blood vessels

  • Arteries (carry blood away from heart, strong and elastic)
  • Veins (carry blood towards heart, wide lumen and valves)
  • Capillaries (allow blood to flow close to cells for diffusion)
• Gas exchange system


  Trachea, intercostal muscles, bronchi, bronchioles, alveoli, diaphragm
• Ventilation


  Ribcage moves up and out, diaphragm moves down, increasing volume and decreasing pressure, drawing air in
• Gas exchange


  Oxygen diffuses from alveoli into blood, carbon dioxide diffuses from blood into alveoli
• Alveoli adaptations


  • Small size and clustered arrangement for large surface area, thin walls for short diffusion pathway, large blood supply
• Blood components


  Plasma, red blood cells, white blood cells, platelets
• Red blood cells


  • Biconcave disc shape, no nucleus, contain haemoglobin
• White blood cells


  • Part of immune system, produce antibodies, engulf pathogens, coordinate immune response
• Alveoli


  Very thin, meaning there is a short diffusion pathway
• Calculating breathing rate


  Divide the number of breaths by the number of minutes
• Components of blood


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


  Liquid that carries the components in the blood: red blood cells, white blood cells, platelets, glucose, amino acids, carbon dioxide, urea, hormones, proteins, antibodies and antitoxins
• Red blood cells


  • Carry oxygen molecules from the lungs to all the cells in the body
  • Have a biconcave disc shape providing a large surface area
  • Have no nucleus allowing more room to carry oxygen
  • Contain the red pigment haemoglobin, which binds to oxygen and forms oxyhaemoglobin
• White blood cells


  • Are a part of the immune system, which is the body's defence against pathogens (microorganisms that can produce disease)
  • Have a nucleus
  • There are a number of types: those that produce antibodies against microorganisms, those that engulf and digest pathogens, and those that produce antitoxins to neutralise toxins produced by microorganisms
• Platelets


  • Help the blood clot form at the site of a wound
  • The clot dries and hardens to form a scab, which allows new skin to grow underneath while preventing microorganisms from entering
  • Small fragments of cells
  • Have no nucleus
  • Without them, cuts would result in excessive bleeding and bruising
• Coronary heart disease


  When the coronary arteries that provide blood to the heart become blocked with the build up of fatty material, resulting in less blood flowing to the heart and reducing its oxygen supply, which may lead to a heart attack
• Stents


  • Metal mesh tubes inserted in arteries to keep them open and allow blood to flow through
  • Effective in lowering the risk of a heart attack
  • Recovery time from surgery is quick
• Factors that may affect health

  • Diet
  • Stress
  • Life situations
• Non-communicable diseases


  Diseases that are not infectious, but have a number of risk factors that increase the likelihood of them occurring