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A-level Biology - 3.1.5 Gas Exchange and the Transport of Oxygen in Living Organisms Part 3

Biology20 CardsCreated about 2 months ago

This deck covers key concepts related to gas exchange and the transport of oxygen in living organisms, focusing on haemoglobin's role and its interaction with oxygen and carbon dioxide.

How many molecules of oxygen can each haemoglobin carry?

4 oxygen molecules
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Key Terms

Term
Definition
How many molecules of oxygen can each haemoglobin carry?
4 oxygen molecules
What happens to haemoglobin in the lungs?
Oxygen joins to haemoglobin in RBCs to form oxyhaemoglobin
What happens to oxyhaemoglobin when it nears body cells?
Oxygen leaves oxyhaemoglobin (dissociates from it) & turns back to haemoglobin
What is partial pressure of oxygen (pO2)?
A measure of oxygen concentration
The greater the concentration of dissolved oxygen in the cells are, the _ the partial pressure is
Higher
Haemoglobin's affinity for oxygen varies depending on…
The partial pressure of oxygen (pO2)

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TermDefinition
How many molecules of oxygen can each haemoglobin carry?
4 oxygen molecules
What happens to haemoglobin in the lungs?
Oxygen joins to haemoglobin in RBCs to form oxyhaemoglobin
What happens to oxyhaemoglobin when it nears body cells?
Oxygen leaves oxyhaemoglobin (dissociates from it) & turns back to haemoglobin
What is partial pressure of oxygen (pO2)?
A measure of oxygen concentration
The greater the concentration of dissolved oxygen in the cells are, the _ the partial pressure is
Higher
Haemoglobin's affinity for oxygen varies depending on…
The partial pressure of oxygen (pO2)
What happens to haemoglobin when there is low pO2?
Oxyhaemoglobin unloads its oxygen ∵ Haemoglobin = low affinity for oxygen Means it releases oxygen rather than combines with it
What happens to haemoglobin when there is high pO2?
Oxygen loads onto haemoglobin to form oxyhaemoglobin ∵ Haemoglobin = high affinity for oxygen Means it will readily combine with oxygen rather than release it
What happens to oxygen when it enters the blood capillaries at the alveoli in the lungs & why?
Alveoli = have high pO2 ∴ oxygen loads onto haemoglobin to form oxyhaemoglobin
What happens to oxygen at respiring cells & why?
When cells respire, use up oxygen = pO2 decreases RBCs deliver oxyhaemoglobin to respiring tissues, where it unloads its oxygen
What do dissociation curves show?
How saturated haemoglobin is with oxygen at any given partial pressure
Why is that when the pO2 is high, haemoglobin has a high saturation of oxygen?
∵ haemoglobin has a high affinity for oxygen so it'll readily combine with oxygen
Why is that when the pO2 is low, haemoglobin has a low saturation of oxygen?
∵ haemoglobin has a low affinity for oxygen so it releases oxygen rather than combine with it
Why is it difficult for the haemoglobin to absorb the 1st oxygen molecule?
∵ 4 polypeptides of haemoglobin molecule are closely united
Why is the dissociation curve 'S-shaped'?
∵ when haemoglobin combines with 1st O2 molecule → conformational change occurs Its shape alters, exposing more subunits to oxygen ∴ makes it easier for other O2 molecules to join But as Hb becomes saturated = harder for more oxygen molecules to join ∴ curve has steep bit in middle where it's really easy for oxygen molecules to join & shadows bits at each end where it's harder
When the curve is steep, a small change in pO2 can cause a…
big change in amount of oxygen carried by Hb (e.g. very small decrease in partial pressure of oxygen = lot of oxygen becoming dissociated from haemoglobin)
Why does haemoglobin rarely achieve 100% saturation of oxygen?
∵ it's very difficult for 4th oxygen molecule to bind
Why do different haemoglobin molecules have different affinities for oxygen? (structure wise)
∵ different haemoglobin molecules have slightly different sequences of amino acids & ∴ slightly different shapes
Haemoglobin gives up its oxygen more readily at _ partial pressures of carbon dioxide (pCO2)
HIGHER
What is the purpose of haemoglobin having a lower affinity for O2 at higher pCO2?
So more oxygen will dissociate into respiring tissues Rapid respiration