Haemoglobin

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  • Created by: Emily.T
  • Created on: 15-01-18 20:19
What is an erythrocyte?
A red blood cell
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How is an erythrocyte specialised for its function?
- Has a biconcave shape giving it a large surface area for the diffusion of gases, also helps them pass through capillaries - Do not have a nucleus to maximise the amount of haemoglobin that fits into the cells
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What is the life cycle of an erythrocyte (red blood cell)?
120 days
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What is haemoglobin (Hb)?
A large globular conjugated protein with a quarternary structure
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Where is haemoglobin found?
In Erythrocytes
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What does haemoglobin do?
Carries oxygen in the blood and gives it its colour
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What is the structure of a haemoglobin molecule?
Has four polypeptide chains which each have a haem (prosthetic) group which contains iron
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How many oxygen molecules can ONE haemoglobin molecule bind to?
4
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Does haemoglobin have a high or low affinity for oxygen?
High
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What does 'affinity for oxygen' mean?
The tendency to combine with oxygen
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Where does oxygen and haemoglobin join?
In the lungs
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What is the molecule called when oxygen and haemoglobin join together?
Oxyhaemoglobin (HbO)
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Is the combining of oxygen and haemoglobin a reversible or irreversible reaction?
Reversible - when oxygen dissociates from oxyhaemoglobin near the body cells, it turns back to haemoglobin
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What is the molecular equation for oxyhaemoglobin?
Hb + 4O2 < -----> Hb(O2)4
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Does oxygen bind tightly or loosely to the haemoglobin?
Loosely
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What happens when the erythrocytes enter the capilliaries in the lungs?
The O2 levels in the cells is relatively low, creating a steep concentration gradient between the inside of the erythrocytes and the air in the alveoli, so O2 moves into RBCs & binds with Hb
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What happens when oxygen binds to a haem group?
As soon as one O2 mol binds, the molecule changes shape to make it easier for the next O2 mol to bind = positive cooperativity
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How is a steep concentration gradient maintained in the lungs?
Because the O2 is bound to the Hb, the free O2 concentration in the erythrocytes stays low and the conc grad is maitained until all of the Hb is saturated with O2.
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What happens when the blood reaches the body tissues?
The conc of O2 in the cytoplasm of body cells is lower than the erythrocytes so O2 moves out of the RBCs down a conc grad. Once the 1st O2 mol is released by the Hb, the mol changes shape again to make it easier to remove the remaining O2 mols
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What is haemoglobin saturation dependent upon?
The partial pressure of oxygen
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What is the partial pressure of oxygen?
A measure of oxygen concentration - the greater the concentration of dissolved oxygen in cells, the higher the partial pressure
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What is the partial pressure of carbon dioxide?
A measure of the concentration of CO2 in a cell
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What does haemoglobin's affinity for oxygen vary on?
The partial pressure of oxygen
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When does oxygen associate (join) with haemoglobin to form oxyhaemoglobin?
Where there's a high partial pressure of oxygen (pO2)
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When does oxyhaemoglobin dissociate (unloads) its oxygen?
When there's a lower partial pressure of oxygen (pO2)
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Where does oxygen enter blood capillaries from?
The alveoli in the lungs
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Why does oxygen enter blood capillaries from the alveoli in the lungs?
Because alveoli have a high pO2 so oxygen loads onto haemoglobin to form oxyhaemoglobin
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Why do body/tissue cells have a lower pO2?
Because the cells are constantly respiring and using up oxygen
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What happens to the oxygen in the capillaries once it reachers respiring tissues?
The oxygen dissociates from the haemoglobin and leaves the erythrocytes to provide oxygen to the cells so they can continue respiring
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Where does the haemoglobin go once they unload all of their oxygen molecules?
They return to the lungs to pick up more oxygen
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What does a oxygen dissociation curve show?
How saturated the haemoglobin is with oxygen at any given partial pressure
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What letter does an oxygen dissociation curve look like?
The letter 'S'
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What are the two variables found on an oxygen dissociation curve?
The partial pressure of oxygen (pO2) and the percentage saturation of haemoglobin with oxygen
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What area of the body is it when the pO2 is high?
The lungs
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What does it mean when the pO2 is high?
Haemoglobin has a HIGH affinity for O2, therefore it will readily combine with oxygen, so it has a HIGH saturation of oxygen
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What area of the body is it when the pO2 is low?
Respiring tissue cells
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What does it mean when the pO2 is low?
Haemoglobin has a LOW affinity for oxygen, therefore it releases oxygen rather than combining with it, so it has a LOW saturation for oxygen
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What does it mean at 0% saturation?
That none of the haemoglobin molecules are carrying any oxygen
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What does it mean at 100% saturation?
That every haemoglobin molecule is carrying the maximum of 4 molecules of oxygen
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Why is the graph 'S' shaped?
Because when Hb combines with the 1st O2 mol, its shape alters in a way that makes it easier for other O2 mols to join, but as the Hb starts to become saturated, it gets harder for more O2 mols to join = curve has a steep part in the middle
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What does the steep part of an oxygen dissociation curve indicate?
That it's really easy for O2 molecules to join
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What do the shallow parts at each end of an oxygen dissociation curve indicate?
That it's really hard for O2 molecules to join
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What does a small change in pO2 do?
It causes a big change in the amount of oxygen carried by the Hb
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What does a relatively small drop in oxygen levels in respiring tissues mean?
That oxygen is released rapidly from the Hb to diffuse into the respiring cells
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Other cards in this set

Card 2

Front

How is an erythrocyte specialised for its function?

Back

- Has a biconcave shape giving it a large surface area for the diffusion of gases, also helps them pass through capillaries - Do not have a nucleus to maximise the amount of haemoglobin that fits into the cells

Card 3

Front

What is the life cycle of an erythrocyte (red blood cell)?

Back

Preview of the front of card 3

Card 4

Front

What is haemoglobin (Hb)?

Back

Preview of the front of card 4

Card 5

Front

Where is haemoglobin found?

Back

Preview of the front of card 5
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