mass transport A

• haemoglobin is a protein with a quaternary structure containing a haem group with Fe 2+
• affinity is the ability for the haemoglobin to bind to oxygen
• saturation of haemoglobin with oxygen is when its holding the maximum amount of oxygen
• loading / association of haemoglobin is the binding of oxygen to haemoglobin
• unloading/ dissociation of haemoglobin is the release of oxygen from haemoglobin
• for haemoglobin to be efficient at transporting oxygen haemoglobin must:

  • readily associate with oxygen at surface of gas exchange / alveoli
  • readily dissociate with oxygen at respiring tissues
• The affinity of oxygen for haemoglobin varies depending on the partial pressure of oxygen which is a measure of oxygen concentration eg:

  The greater the concentration of dissolved oxygen in cells = greater the partial pressure.

  partial pressure increases = the affinity of haemoglobin for oxygen increases (oxygen binds to haemoglobin tightly)
• when carbon dioxide is present it changes the shape of haemoglobin as it is acidic so denatures protein so it binds more loosely to oxygen and releases it - LOWER AFFINITY
• in alveoli:

  • oxygen concentration = high
  • carbon dioxide concentration = low

  Affinity = HIGH = OXYGEN IS ASSOCIATED
• in respiring tissue:

  • oxygen concentration = low
  • carbon dioxide concentration = high

  Affinity = LOW = OXYGEN IS DISSOCIATED
• Different haemoglobin = different affinities

  I

  Different molecular shapes = slightly different amino acid sequence

  I

  Slightly different tertiary and quaternary structure

  I

  Different oxygen binding properties
• oxygen dissociation curve shows the relationship between saturation of haemoglobin with oxygen and the partial pressure of oxygen

  
• Sigmoid curve/ s-shape explanation:

  1. initially shallow = four polypeptide subunits close together so hard for first O2 molecule LOW OXYGEN CONC = LOW AFFINITY

  2. gradual increase = binding of first O2 makes it easier so INDUCES other subunits to bind to O2 molecule (slightly changes 3d shape of protein)

  3. gradient steepens = POSITIVELY COOPERATIVITY binding of first makes it easier so increase in partial pressure of O2 to bind to second

  4. gradient reduces and plateaus = harder PROBABILITY as 3/4 binding sites occupied

  
• The Bohr effect is when their is high conc of CO2 causing oxyhaemoglobin curve to shift to the RIGHT - affinity decreases as acid changes shape of the haemoglobin (unloads easier)
• oxygen-dissociation curve:

  • curve further to LEFT = HIGHER AFFINITY (loads easier)

  e.g. foetus, llama, earthworm

  curve further to RIGTH = LOWER AFFINITY (unloads easier)

  [ :) more readily unloads at respiring tissues]

  e.g. dove
• mammalian circulatory system is closed and double circulatory - blood remains in blood vessels and blood passes through the heart twice
• double circulatory system manages the pressure of blood flow:

  HIGH pressure = heart to body (oxygenated blood) ensuring blood reaches all respiring cells in body

  LOW pressure = lungs prevent damage to capillaries and reduces speed for blood flow so more time gas exchange
• coronary arteries supply heart/ cardiac muscle with oxygenated blood so they continually contract and relax
• veins in the heart: vena cava and pulmonary vein
• arteries in the heart: aorta and pulmonary artery
• vessels in the lungs: pulmonary vein and pulmonary artery
• vessels in the kidney: renal artery and renal vein
• arteries ---> arterioles ---> capillaries ---> veins
• aterioles are smaller than arteries and are connected to capillaries
• properties of arteries:

  • thicker muscle layer than veins = constriction and dilation control volume of blood
  • thicker elastic layer than veins = maintain blood pressure so walls can stretch and recoil (heart beat)
  • thicker walls than veins = high pressure prevent bursting
  • narrow lumen
• properties of veins:

  • relatively thin muscle layer = cant control blood flow
  • relatively thin elastic layer = low pressure
  • thin walls = low pressure (less burst risk) and easily flatten helps flow of blood up to the heart
  • has valves = prevent backflow
  • large lumen = low pressure
• Capillaries are the smallest blood vessels, site of metabolic exchange, only one cell thick for fast exchange of substances.
• cardiac muscle is the thick muscular layer in the walls of the heart
• properties of cardiac muscle:

  • it is myogenic = can contract and relax w/o nervous system or hormonal stimulation
  • never fatigues = as long as it has a supply of oxygen
• coronary arteries surround the heart and supply cardiac muscle with oxygenated blood so it never fatigues (branch off from aorta so always supplied with oxygenated blood)

  A) aorta

  
• four chambers of the heart: right and left atrium and the left and right ventricle
• atriums have

  • thinner muscular walls than ventricles (don't need to contract as hard as only transport blood to ventricle)
  • elastic walls that stretch when blood enters
• ventricles have

  • thicker muscular walls that enable bigger contraction at higher pressure to transport blood further distance to reast of the body
• right ventricle is to the LUNGS so has thinner muscular wall than left ventricle as blood flowing at low pressure to prevent damage to capillaries and for slow blood flow for gas exchange
• left ventricle is to the BODY so has a thicker muscular wall than right as blood flows at higher pressure from larger contractions to assure all blood reaches all cells in the body
• blood from body to heart to lungs:

  1. vena cava [deoxy blood]
  2. right atrium
  3. RIGHT ATRIOVENTRICULAR VALVE
  4. right ventricle
  5. PULMONARY SEMI LUNAR VALVE
  6. pulmonary artery
• blood from lungs to heart to body:

  1. pulmonary vein
  2. left atrium
  3. LEFT ATRIOVENTRICAL VALVE
  4. left ventricle
  5. AORTIC SEMI LUNAR VALVE
  6. aorta
• semi lunar valve found in aorta and pulmonary artery
• atrioventricular valves found between atria and ventricle
• the septum is the cardiac muscle that runs down the middle of the heart to sperate left and right side of the heart/ oxygenated and deoxygenated blood

  MAINTAINS HIGH CONC GRADIENT TO ENABLE DIFFUSION AT RESPIRING CELLS