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, some have a low optimum pH
• If the pH or temperature is too high or too low, the enzyme will be denatured and can no longer work
• Types of enzymes in the digestive system

  • Carbohydrases
  • Proteases
  • Lipases
• Carbohydrases


  Convert carbohydrates into simple sugars
• Proteases


  Convert proteins into amino acids
• Lipases


  Convert lipids into fatty acids and glycerol
• 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, released into the small intestine
  • Alkaline to neutralise hydrochloric acid
  • Emulsifies large fat droplets into smaller ones
• Investigating the effect of pH on an enzyme controlled reaction

  1. Use iodine to detect presence of starch

  2. Warm amylase, starch and buffer solution

  3. Take samples at regular intervals and test with iodine

  4. Time when starch is completely broken down

  5. Calculate rate using 1000/time
• In experiments measuring product formation or reactant use over time, rate = change/time
• Heart


  An organ in the circulatory system, pumps blood around the body in a double circulatory system
• Structure of the heart

  • Muscular walls
  • 4 chambers
  • Valves
  • Coronary arteries
• Blood flow through the heart

  1. Blood flows into right atrium and right ventricle, pumped to lungs

  2. Oxygenated blood flows into left atrium and left ventricle, pumped around body
• Natural resting heart rate

  Controlled by pacemaker cells in the 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
  • Veins
  • Capillaries
• Arteries


  • Carry blood away from the heart, have layers of muscle and elastic fibres in the walls
• Veins


  • Carry blood towards the heart, have a wide lumen and valves to ensure one-way flow
• Capillaries


  • Allow blood to flow very close to cells, have one cell thick permeable walls
• The rate of blood flow is calculated from volume of blood/number of minutes
• Components of the gas exchange system

  • Trachea
  • Intercostal muscles
  • Bronchi
  • Bronchioles
  • Alveoli
  • Diaphragm
• Ventilation


  1. Ribcage moves up and out, diaphragm moves down, increasing chest volume and decreasing pressure

  2. Air is drawn into the chest as it moves from high to low pressure
• Gas exchange in the alveoli

  1. Oxygen diffuses from alveoli into capillary blood

  2. Carbon dioxide diffuses from capillary blood into alveoli
• Alveoli


  • Very small and arranged in clusters, creating a large surface area
  • Capillaries provide a large blood supply
  • Walls are very thin, short diffusion pathway
• Breathing rate is calculated by dividing 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


  • Carry oxygen molecules, have a biconcave disc shape, no nucleus, contain haemoglobin
• White blood cells


  Part of the immune system, defend against pathogens
• Types of white blood cells

  • Those that produce antibodies
  • Those that engulf and digest pathogens
  • Those that coordinate the immune response
• Alveoli


  Very thin, meaning there is a short diffusion pathway