✅7 - Mass Transport Flashcards
What is associating?
When haemoglobin binds with oxygen
Where does loading take place?
In the lungs
What is dissociating?
When haemoglobin releases its oxygen
Where does unloading take place?
The tissues
Haemoglobins with a high affinity for oxygen…
…take it up easily but release it less easily
Haemoglobins with a low affinity for oxygen…
…don’t take it up easily but release it easily
What is the role of haemoglobin?
To transport oxygen
What features must haemoglobin have to be efficient at transporting oxygen?
Readily dissociate with oxygen at the surface where gas exchange occurs
Readily dissociate from oxygen at the tissues requiring it
When does haemoglobin change affinity?
Under different conditions, such as O2 and CO2 concentrations
Why do different haemoglobins have different affinities for oxygen?
Because they have different shapes as each species produces a different amino acid sequence so the tertiary and quaternary structure are different
What is an oxygen dissociation curve?
The graph of the relationship between the saturation of haemoglobin and oxygen partial pressure
At low oxygen concentrations, why does little oxygen bind to haemoglobin?
Because the shape of the haemoglobin molecule makes it difficult for the first oxygen molecule to bind to one of the sites on its four polypeptide subunits because they are closely united
Why is it easier for the second oxygen molecule to bind to haemoglobin?
Because the binding of the first oxygen molecule changes the quaternary structure of the haemoglobin and makes it easier for other subunits to bind to an oxygen molecule
What is positive cooperativity?
Binding the first molecule makes binding of the second easier and so on
What happens after the binding of the third oxygen molecule?
It is harder to bind the fourth, as the majority of the binding sites are filled and it is less likely that a single oxygen molecule will find an empty site to bind to
What is the shape of the oxygen dissociation curve?
Sigmoidal
The further the curve is to the left…
…the greater the affinity of haemoglobin for oxygen
The further the curve is to the right…
…the lower the affinity of haemoglobin for oxygen
How does haemoglobin’s affinity for oxygen change in the presence of carbon dioxide?
Its affinity is reduced
What is the Bohr effect?
The greater the concentration of Carbon Dioxide, the more rapidly haemoglobin releases its oxygen
Why is a transport system required?
To take materials from cells to exchange surfaces and the environment
What factors does the presence of a transport system depend on?
The surface area to volume ratio
How active an organism is
What are the features of transport system?
A suitable medium in which to carry materials
A form of mass transport
A closed system of tubular vessels
A mechanism for moving the transport medium within vessels
What do animals use as transport mechanisms?
Muscular contraction either of the body muscles or of the organs eg heart
What do plants rely on for exchange?
Natural, passive processes such as evaporation
What kind of circulatory system to mammals have?
A closed, double system
Why does the blood pass through the heart twice for reach circuit of the body?
Because pressure is reduced when the blood is passed through the lungs, and it otherwise would circulate the body very slowly
What is the atrium?
A thin walled and elastic chamber which stretches as it collects blood
What is the ventricle?
A much thicker, more muscular chamber
Why do the ventricles have thicker more muscular walls?
Because they have to contract strongly to pump blood a further distance
Where does the right ventricle pump blood to?
The lungs
Where does the left ventricle pump blood to?
The rest of the body
What are the two valves?
The left atrioventricular (bicuspid)
The right atrioventricular (tricuspid)
What is the problem with the large surface area needed for the capillaries in the lungs?
There has to be a significant drop in pressure
What is the aorta connected to?
The left ventricle
What does the aorta do?
Carries oxygenated blood to all parts of the body except the lungs
What is the vena cava connected to?
The right atrium?
What does the vena cava do?
Brings deoxygenated blood back from the tissues of the body