Mass transport in animals

• What is the evidence that haemoglobin has a quaternary structure

  • it is composed of 4 sub units, each containing a haem group
  • each haem group can combine to an oxygen molecule
• what is made when haemoglobin combines with oxygen

  oxyhaemoglobin
• explain the term partial pressure

  the amount of a particular gas in a mixture of gases or a solution
• where is the partial pressure of oxygen highest in the body

  the alveoli in the lungs
• Why is the partial pressure of oxygen lower in tissues

  the partial pressure of oxygen is lower in the tissues as the tissues respire so the haemoglobin unloads the oxygen to respiting tissues
• explain why the oxygen dissociation curve is sigmoid shaped

  because the firs oxygen molecule binds to the haemoglobin, this changes the tertiary structure of haemoglobin which uncovers another haem group for oxygen to bind to

  this makes it easier for the next oxygen molecule to combine with the haemoglobin
• sketch a curve to show Bohr shift

  • the bohr shift is when the haemoglobin-oxygen dissociation curve shifts to the right due to the affinity of haemoglobin for oxygen getting lowered by increasing carbon dioxide concentration

  if carbon dioxide levels increase the saturation of haemoglobin decreases
• explain which organisms haemoglobin will have the highest affinity and the lowest affinity, using your diagram to help

  -
• state the function of the valves


  valves ensure that the blood flows in one direction only through the heart

  they open and close due to pressure differences either side of the valves
• describe the events of the cariac cycle relating to the changes in volume and pressure and associated valve movements (6)


  1. atrial systole
  2. atria contract and ventricles relax pushing the blood from the atria to the ventricles from an area of high blood pressure to low blood pressure
  3. atrioventricular valve open and semi lunar valve closed
  4. ventricular systole
  5. ventricles contract and atria relax
  6. atrioventricular valves close to prevent any backflow of blood and semilunar valves open and blood is forced into the arteries
  7. diastole
  8. ventricles and atria are both relaxed
  9. semilunar valves close preventing any backflow of blood and the atrioventricular valves open as blood is pushed back into the atria, increasing the blood pressure for the cycle to start again
• define the term cardiac output

  • the volume of blood expelled from the left ventricle per minute
• define the term heart rate

  • the number of cardiac cycles per minute
• define the term stroke volume

  • the volume of blood expelled from the left ventricle in one heart beat
• state the equation foe cardiac output

  CO = SV x HR

  
  

  sv - stroke volume

  hr - heart rate
• define mass transport

  • the bulk movement of liquids and gases due to a pressure difference
• why do large, active, multicellular organisms need a blood transport system

  • because they have small surface area to volume ratios
  • and are more active
  • so a greater need for a specialised transport system with a pump
• draw and label a simple double circulatory system

  -
• state why a double circulatory system is required

  • when blood passes through the lungs capillaries the pressure is reduced. this is due to the large cross section area of the lung capillaries and the narrow lumen of the capillaries creating friction which slows down the blood
  • blood is therefore returned to the heart to boost its pressure before being circulated to the rest of the body
• name the blood vessels entering and leaving the kidney

  entering - renal artery

  leaving - renal vein
• describe the structure of the arteries and how it relates to its function

  transports blood from the heart to the organs

  ENDOTHELIAL LAYER -

  • only one cell thick
  • gives smooth layer to reduce friction and give smooth flow #

  ELASTIC TISSUE -

  • contains a large amount of elastic protein fibres
  • allows wall to stretch as pulse of blood flows past. stops pressure rising too high
  • recoils once blood passes, maintains a pressure on the blood

  MUSSCLE TISSUE

  OUTER LAYER -

  • made of fibrous proteins and gives support and strength to wall, helping it to resist damage do to high pressure of the blood inside
• describe the structure of the arterioles and how it relates to its function

  arterioles are smaller vessels than arteries and connect artery to capillary

  as the vessel diameter is smaller than artery, there is more friction between the blood vessel and the wall, causing a fall in blood pressure

  • the structure of an arteriole is same as artery but 2 main diffs

  1. the elastic layer is thinner as blood pressure is lower. there is less need for the elasticity required to allow the pulse of blood to pass
  2. the muscle layer is thicker. the muscles in the arterioles contract to constrict the vessel (vasoconstriction). the muscle can also relax to cause the vessel to dilate (vasodilation) this allows more blood into organ
• describe the structure of the capillaries and how it relates to its function

  • wall has only one cell thick endothelial layer
  • this gives a short diffusion pathway for the exchange of materials between blood and the tissue cells
  • diameter is very small and there is a large number of capillaries. this creates friction and the blood pressure created by the heart is lost as blood flows through the capillaries
• describe the structure of the veins and how it relates to its function

  • veins carry blood back to the heart from the tissues
  • the blood is under low pressure, therefore the vein wall does not need to be thick

  STRUCTURE -

  • muscle layer is very thin. there is no need for vasoconstriction as all the blood is going back to heart
  • elastic layer is thin. pressure is very low and the wall does not need to stretch or recoil
  • the veins have valves. the residual blood pressure is very low. the blood is moved along the vein by squeezing action of skeletal muscles when they contract. the valves only allow the blood to pass through in one direction to ensure blood goes back to heart
• explain why arteries and veins are classified as organs

  • because they are both consist of different tissues working together to form an organ
• what is tissue fluid

  the space between the cells in tissue is filled with fluid known as tissue fluid

  it is formed from water leaving the capillaries
• describe how tissue fluid is formed and returned to the blood (6)

  1. the blood has a high hydrostatic pressure, at the arteriole end of the capillaries
  2. this forces water and other small molecules out of the capillaries
  3. forming tissue fluid - exchange of gases and nutrients between the tissue and the cells
  4. large plasma proteins remain in the blood as they are too big to leave the capillary
  5. this lowers the water potential inside the capillary at the venule end of the capillary
  6. water moves back into the capillary by osmosis
  7. excessive tissue fluid is absorbed by lymph vessels