organisms exchange substances with environment

• 4 chambers of the heart:

  right atrium

  right ventricle

  left atrium

  left ventricle
• structure of atria:

  • have thinner muscular walls
  • do not need to contract as hard as pumping blood to ventricles
• structure of ventricles:

  • thicker muscular walls for bigger contraction creates high blood pressure to pump blood to lungs for right ventricle and to the whole body for the left ventricle
• 2 types of veins:

  • vena cava
  • pulmonary vein
• vena cava = body vein

  • carries deoxygenated blood from the body into the right atrium
• pulmonary vein:

  • pulmonary = linked to the lungs
  • carries oxygenated blood from lungs to left atrium
• haemoglobin:

  • proteins with a quaternary structure
  • they transport oxygen
• partial pressure = amount of oxygen available

  low partial pressure = less oxygen available

  high partial pressure = lots of oxygen available
• oxyhaemoglobin dissociation curve:

  • oxygen loaded in regions with a high partial pressure of oxygen e.g alveoli
  • oxygen unloaded in regions of low partial pressure of oxygen e.g respiring tissues
• higher affinity = binds to oxygen more easily

  lower affinity = releases oxygen more easily
• positive cooperativity:

  • shape of molecule makes it difficult for oxygen to bind to
  • binding of first oxygen molecule = change in quaternary structure of haemoglobin = change in shape = more easing for other oxygen molecules to bind
• what is the bohr effect?

  high co2 conc = decrease in PH due to being more acidic = change in shape of haemoglobin = oxygen binds less easily so lower affinity
• where is there a low partial pressure of co2

  alveoli
• where is there HIGH partial pressure of co2


  respiring tissues
• how is haemoglobin adapted for llamas?

  llamas found at high altitudes where there is low partial pressures of oxygen so they have haemoglobin with a higher affinity
• adaptation of haemoglobin for doves:

  doves have faster metabolism so need more oxygen for respiration so have a lower affinity for oxygen so can unload easier
• double circulatory system:

  • blood passes through heart twice in each circuit
  • to the lungs
  • to the rest of the body
• what is cardiac muscle?

  thick muscular layer in the walls of the heart
• coronary arteries

  • supply cardiac muscle with oxygenated blood so it dosent fatigue
  • they branch of from the aorta
• blocked coronary arteries = no oxygen supplied = no respiration = cells dying = heart attack
• why is blood pumped at low pressure at right ventricle

  to prevent damage to capillaries in the lungs
• 4 key blood vessels:

  • aorta
  • pulmonary artery
  • vena cava
  • pulmonary veins
• pulmonary artery carries blood from right ventricle to lungs
• aorta carries oxygenated blood from left ventricle to rest of body
• valves prevent backflow of blood
• semi lunar valves are in the aorta and pulmonary artery
• atriaventricular valves are between atria and ventricles
• arteries carry blood away from the heart into the arterioles
• arterioles are smaller than arteries and connect to the capillaries
• capillaries connect arterioles to veins
• veins return deoxygenated blood to the heart
• structure of arteries in relation to function:

  • thick muscular layer so can constrict and dilate
  • thick elastic layer so walls can stretch to maintain high blood pressure
  • thick walls to prevent vessels bursting
• vein structure related to function:

  • thin muscular layer so cant control blood flow
  • thin elastic layer as pressure is lower
  • thin wall thickness as low risk of vessels bursting due to low pressure
• structure of arterioles in relation to function:

  • thicker muscular layer to allow constriction of lumen to restrict blood flow into capillaries
  • thin elastic layer due to lower pressure
• capillary structure related to function:

  • highly branched so large surface area for exchange
  • narrow lumen / one cell thick to reduce diffusion distance
• cardiac output is the volume of blood which leaves 1 ventricle in 1 minute
• cardiac output = heart rate x stroke volume

  heart rate is beats of heart per min

  stroke volume is volume of blood that leaves heart each beat
• what is tissue fluid?


  fluid containing glucose, amino acids, ions, oxygen
• transpiration is the loss of water vapour from the stomata by evaporation
• how light affects transpiration

  more light = more stomata open = larger sa for evaporation