mass transport

• haemoglobin 


  protein molecules with quaternary structure that has evolved to make it efficient at loading and unloading oxygen under sets of conditions
• quaternary structure of haemoglobin

  four polypeptide chains linked to form almost spherical molecule

  each polypeptide associated with Haem group

  each haem group contains Fe2+ ion which can combine with single oxygen molecule

  can carry total of 4 oxygen molecules
• haemoglobin and loading / associating of oxygen 


  process by which haemoglobin binds with oxygen

  lungs
• haemoglobin and offloading / dissociating of oxygen

  process by which haemoglobin releases oxygen

  tissues
• haemoglobin and affinity


  high affinity = take up oxygen more readily, release it less easily

  low affinity = take up oxygen less readily, release it easily
• things haemoglobin must to be efficient as transporting oxygen 


  readily associate with oxygen at gas exchange surface

  readily dissociate with oxygen at respiring tissues
• why are there different haemoglobin

  each species produced haemoglobin with slightly different amino acid sequence

  each have slightly different tertiary and quaternary structure and different oxygen binding properties
• oxygen dissociation curves of haemoglobin 


  different partial pressures of oxygen = doesnt bind evenly

  • shape of haemoglobin molecule makes binding of first molecule difficult as they are closely united - at low concentrations little oxygen binds
  • binding of first molecule changes quaternary structure, changing its shape = exposes of bases for molecules 2 / 3 = smaller increase in partial pressure required
  • POSITIVE COOPERATIVITY
  • majority of binding sites occupied = less likely for binding of 4th molecule
• shifts to oxygen dissociation curves and haemoglobin

  shift to LEFT = greater affinity ( loads easily, unloads harder )

  shift to RIGHT = lower affinity ( loads harder, unloads easier )
• effect of carbon dioxide concentration on haemoglobin - BOHR EFFECT

  reduced affinity in presence of carbon dioxide

  • gas exchange surface = low concentration of carbon dioxide, increases affinity of haemoglobin, couples with high concentration of oxygen in lungs = readily loaded (shift in curve to left)
  • respiring tissues = high concentration of carbon dioxide = acidic carbonic acid, low pH causes shape change in haemoglobin = more readily dissociates
• haemoglobin and loading, transporting and unloading oxygen

  gas exchange surface, co2 constantly removed

  pH slightly raised due to low concentration of co2

  higher pH changes shape = enables it to readily load oxygen

  shape increases affinity of haemoglobin for oxygen so it isnt released in transportation in blood

  co2 produced by respiring cells

  co2 acidic ( carbonic acid ), pH of blood in tissues lowered = changes shape of haemoglobin

  lower affinity for oxygen = releases oxygen more easily into respiring tissue
• active tissue and more oxygen unloading

  higher rate of respiration

  more carbon dioxide tissues produce

  lower the pH is

  greater haemoglobin shape change

  more readily unloading

  more oxygen available for respiration
• haemoglobin of animals in high altitudes

  low partial pressure of oxygen = haemoglobin with higher affinity of oxygen

  e.g., llama
• why large organisms have transport system

  increasing size = surface area to volume ratio decreases

  needs of organism cannot be met by body surface alone = specialist exchange surfaces required
• 2 factors influencing existence of specialised transport pump / medium

  surface area to volume ratio

  how active organism is
• features of transport systems

  suitable medium to carry materials, usually water based liquid as water readily dissolves substances and be moved around easily

  form of mass transport in which transport medium move around in bulk over large distances, faster than diffusion

  closed system of tubular vessels containing transport medium and forms branching network for distribution

  mechanism for moving transport medium within vessels, requiring pressure difference
• how are pressure differences necessary for moving transport medium in transport systems created

  animals use muscular contraction either of body muscles or of specialised pumping organ

  plants rely on natural, passive processes such as evaporation of water

  • mechanism to maintain mass flow in one direction
  • means of controlling flow of transport medium to suit changing needs of different parts
  • mechanism for mass flow of water or gases
• circulatory system in mammals

  closed double circulatory system

  blood confined to vessels and passes twice through heart for one circuit

  • blood pressure reduced once passes through lungs = circulation would be very slow
  • necessary for high pressure and fast circulation as mammals have high body temperature and hence high rate of metabolism
• right ventricle


  pumps blood only to lungs and has thinner muscular wall than left ventricle
• left ventricle


  thick muscular wall, enabling it to create enough pressure to pump blood to rest of heart
• 2 groups of valves between atrium and ventricles

  left ATRIOVENTRICULAR (bicuspid) valves

  right ATRIOVENTRICULAR (tricuspid) valves
• atria


  receive blood from veins
• pulmonary vessels

  vessels connecting heart to lungs
• 4 vessels connected to four chambers

  aorta

  vena cava

  pulmonary artery

  pulmonary vein
• aorta

  connected to left ventricle

  carried oxygenated blood to all parts of heart minus lungs
• vena cava


  connected to right atrium

  brings deoxygenated blood back from body tissues, minus lungs
• pulmonary artery


  connected to right ventricle

  carries deoxygenated blood to lungs
• pulmonary vein


  connected to left atrium

  brings oxygenated blood back from lung
• supplying heart muscle with oxygen


  heart does not use oxygen from blood passing through it

  heart muscle supplied by coronary arteries which extend from aorta

  blockages of arteries = myocardial infection as area of heart muscle deprived of blood and oxygen, cells unable to aerobically respire and die
• 2 phases of cardiac cycle

  contraction of heart = systole

  relaxation of heart = diastole
• 2 types of systole

  atrial systole

  ventricular systole
• relaxation of heart - diastole

  blood returns to atria from lungs from pulmonary vein and body from vena cava

  atria fill = pressure increases

  when pressure exceeds that in ventricles, AV valves open

  passage of blood aided by gravity

  walls of atria and ventricles relaxed

  relaxation of ventricle walls cause them to recoil and reduce pressure within ventricle

  causes lower pressure than in aorta and pulmonary artery, SEMI LUNAR values in aorta / pulmonary artery close
• contraction of heart - atrial systole

  contraction of atrial walls and recoil of relaxed ventricle walls forces remaining blood into ventricles from atria

  muscle of ventricle relaxed
• contraction of heart - ventricular systole 


  after short delay allowing ventricles to fill with blood, walls contract simultaneously

  increases blood pressure within them, forcing shut AV valves and preventing back flow into atria

  AV valves closed = pressure in ventricles rises

  exceeds that in aorta and pulmonary artery, blood forced from ventricles

  ventricles have thick muscular walls = contract forcefully, necessary to create high pressure needed to pump blood around body

  left ventricle = blood to extremities

  right ventricle = blood to lungs
• valves in control of blood flow

  valves prevent unwanted back flow of blood where pressure differences would result in blood flowing in opposite regions

  designed to open when pressure difference favours blood movement in desired direction
• 3 types of valve

  atrioventricular valves

  semi-lunar valves

  pocket valves
• atrioventricular valves


  between atria and ventricles

  prevent back flow when ventricle contraction means ventricular pressure exceeds atrial pressure
• semi-lunar valves


  aorta and pulmonary artery

  prevent back flow intro ventricles when pressure in vessels exceeds ventricles
• pocket valves


  veins

  occur throughout veinous system

  ensure when veins are squeezed blood flows back to heart rather than away
• 4 types of blood vessel

  arteries

  arterioles

  capillaries

  veins