mass transport in animals Flashcards
what is the structure of a haemoglobin?
- primary structure: sequence of amino acids in the polypeptide chain.
- secondary structure: polypeptide chains are coiled into a helix.
- tertiary structure: polypeptides folded into a specific shape to carry out their function.
- quaternary structure: polypeptides linked to make a spherical molecule
what is each polypeptide associated with in a haemoglobin?
haem group: contains an Fe2+ ion.
how many oxygen molecules can an Fe2+ combine with?
1, so 4 can be carried by a single haemoglobin.
what is the loading/ associating process?
haemoglobin binding with oxygen.
happens in the lungs.
what is the unloading/ dissociating process?
haemoglobin releases oxygen.
happens at the tissues.
what is high affinity?
haemoglobin take up oxygen more easily, but release it less easily.
what is low affinity?
haemoglobin take up oxygen less easily, but release it easily.
what is the role of haemoglobin?
to transport oxygen.
how are haemoglobin adapted to transport oxygen?
- readily associate with oxygen at the surface where gas exchange takes place.
- readily dissociate with oxygen at tissues.
how does haemoglobin change its affinity?
changes its shape in the presence of certain substances.
what is the oxygen dissociation curve?
the graph of the relationship between the saturation of haemoglobin with oxygen and the partial pressure of oxygen.
how can you explain the shape of the oxygen dissociation curve?
- the first oxygen is difficult to bind to because the polypeptide subunits are closely united - gradient is shallow initially.
- binding of the first oxygen molecule changes the quaternary structure so induces subunits to bind.
- second haemoglobin needs a smaller partial pressure to bind - gradient steepens.
- after the binding of the third molecule, it gets harder again because the majority of binding sites are occupied - gradient levels off.
what does it mean if the oxygen dissociation curve is further to the left?
greater affinity of haemoglobin for oxygen.
what does it mean if the oxygen dissociation curve is further to the right?
lower affinity of haemoglobin for oxygen.
what is the effect of carbon dioxide concentration on the affinity for oxygen?
haemoglobin have less affinity for oxygen.
oxygen is released.
Bohr effect.
what is the CO2 concentration at gas exchange surfaces?
low because it diffuses across the exchange surface and is excreted from the organism.
affinity for oxygen is increased.
oxygen dissociation curve shifts to the left.
what is the CO2 concentration at respiring tissues?
high because the affinity for oxygen is reduced .
oxygen dissociation curve shifts to the right.
how does the body ensure there is always efficient oxygen at respiring tissues?
higher rate of respiration -> more CO2 produced by tissues -> lower pH -> greater haemoglobin shape change -> oxygen dissociated more readily -> more oxygen available for respiration.
what is the cardiac cycle?
the sequence of events taking place during one complete heartbeat.
what is systole?
periods when the heart is contracting.
what is diastole?
periods when the heart is relaxing
what happens during passive filling of the ventricles?
- atria and ventricles are relaxed.
- AV valves are open, semi-lunar valves are closed.
3.blood flows passively from the atria through the AV valves and into the ventricles.
what happens during atrial systole?
- passive filling continues until the ventricles are 70% full.
- increased volume of blood in the ventricles forces AV valves closed.
- atria contract and blood is propelled into the ventricles.
what happens during isometric ventricular contraction?
- both sets of valves are closed, atria and ventricles are relaxed.
- ventricles begin to contract but the muscles can’t change in length - isometric contraction.
- pressure in the ventricles builds up.
