Mass transport in Animals

• why is a circulatory system needed

  cells in organisms need constant supply of reactants for metabolism large organisms are to big for simple diffusion so exchange surfaces connected to circulatory system
• what is mass transport

  bulk movement of gases or liquids in one direction , via a system of vessels and tubes
• importance of mass transport

  maintain diffusion gradients at exchange site and surroundings

  help bring substances quickly from one exchange site to another

  help ensure effective cell activity by keeping immediate fluid environment of cells within a suitable metabolic range
• how is the circulatory a mass transport system

  is a one way flow system that transports essential nutrients and gases to all cells of body
• which parts of heart are associated with oxygenated blood

  pulmonary vein

  Left ide of heart (atrium + ventricle)

  Aorta
• which parts of heart associated with deoxygenated blood

  Pulmonary artery

  right side of heart (atrium + ventricle)

  Vena Cava
• what is haemoglobin


  a globular protein which is an oxygen carrying pigment found in quantities in red blood cells
• how are red blood cells adapted for function

  biconcave which increases surface area creating high surface area to volume ratio for diffusion

  Do not contain a nucleus which provides more space to carry haemoglobin so they can transport as much oxygen as possible
• Structure of haemoglobin

  has a Quaternary structure as made of four polypeptide chain

  Each chain has a prosthetic haem group and are held together by disulphide bonds with hydrophilic R groups facing outwards to maintain solubility and hydrophobic R groups facing outwards to preserve spherical shape

  prosthetic haem group contains iron II which can reversibly combine with oxygen to form oxyhaemoglobin. Each haem group ca carry four oxygen molecules and is same for all types of haemoglobin
• function of haemoglobin 


  responsible for binding to oxygen in lungs and transporting it around body in blood as oxygen is not very soluble in water

  presence of iron II ion allows oxygen to reversibly bind so can be deposited at tissue and cells
• what is formed when oxygen binds to haemoglobin

  Oxyhaemoglobin formed

  4O2+Hb->Hb4O2 (reversible occurs when oxygen dissociates in tissue)
• what is cooperative binding in haemoglobin

  The binding of the first oxygen molecule results in a conformational change in the structure of the haemoglobin molecule, making it easier for each successive oxygen molecule to bind
• what is oxygen dissociation curve 


  shows rate at which oxygen associates and dissociates with haemoglobin at different partial pressures of oxygen (pO2)
• what is partial pressure of oxygen

  Pressure exerted by oxygen within a mixture f gases , measure of oxygen concentration .
• what is haemoglobin saturation

  when all its binding sites are taken up by oxygen , contains four oxygen molecules
• what is oxygen affinity 


  the was which haemoglobin binds and dissociates with oxygen , high affinity binds and dissociates easily
• why is the dissociation curve , curved

  difficulty binding to first oxygen molecule so shallow curve at bottom left corner of graph

  first oxygen molecule bound changes shape of haemoglobin protein molecule so easier for next molecules to bind speeding up rate creating steep part of graphs

  As it approaches saturation of fourth oxygen molecule binding it takes longer due to shortage of binding sites so leveling off of curve in top right corner of graph
• How to interpret the graph

  When read left to right it provides information about rate at which haemoglobin binds to oxygen

  When read right to left provides info about rate at which haemoglobin dissociates
• what is the Bohr shift

  changes in dissociation curve due to carbon dioxide levels when partial pressure of co2 in blood is high haemoglobin affinity to oxygen is reduced
• Why does Bohr shift happen

  Co2 binds with water to form carbonic acid

  carbonic acid dissociates into hydrogen carbonate ions and hydrogen ions

  hydrogen ions bind to haemoglobin causing release of oxygen
• benefits of Bohr shift 


  helpful as it means haemoglobin gives up oxygen more readily in respiring tissue when needed
• which way does Bohr shift , shift the graphs

  shifts graph to the right so at any partial pressure of oxygen saturation is lower at higher co2 levels
• What is cardiac output and equation

  Term used to describe volume of blood pumped by heart per unit of time

  cardiac output = heart X stroke volume
• how has haemoglobin adapted for animals living at high altitudes

  adapted as haemoglobin binds more readily to oxygen which allows them to obtain a sufficient amount of oxygen saturation when partial pressure lower (curve shifts left)
• how has foetal haemoglobin adapted

  has higher affinity for oxygen than adult

  allows fetus to obtain oxygen from mother placenta at low partial pressure
• why is it important for foetuses to gain adult haemoglobin

  adult haemoglobin dissociates quicker as lower affinity so oxygen can go to respiring tissue for baby growth