Carrying oxygen in the blood Haemoglobin

Oxygen is carried in red blood cells bound to the protein haemoglobin The haemoglobin molecule consists of four polypeptide chains, with a haem group at the centre of each chain. Each haem group contains one iron atom One oxygen molecule binds to each iron atom

Oxygen is carried in red blood cells bound to the protein haemoglobin

The haemoglobin molecule consists of four polypeptide chains, with a haem group at the centre of each chain.

Each haem group contains one iron atom

One oxygen molecule binds to each iron atom

So one haemoglobin molecule can bind up to four oxygen molecules

So one haemoglobin molecule can bind up to four oxygen molecules

A sample of blood can therefore be in any state from completely deoxygenated (0% saturated) to fully oxygenated (100% saturated). Since deoxyhaemoglobin and oxyhaemoglobin are different colours, it is easy to measure the % saturation of a sample of blood in a colorimeter

A sample of blood can therefore be in any state from completely deoxygenated (0% saturated) to fully oxygenated (100% saturated).

Since deoxyhaemoglobin and oxyhaemoglobin are different colours, it is easy to measure the % saturation of a sample of blood in a colorimeter

As the chemical equation shows, oxygen drives the reaction to the right, so the more oxygen there is in the surroundings, the more saturated the haemoglobin will be. This relation is shown in the oxygen dissociation curve :

As the chemical equation shows, oxygen drives the reaction to the right, so the more oxygen there is in the surroundings, the more saturated the haemoglobin will be.

This relation is shown in the oxygen dissociation curve :

Oxygen dissociation curve Note: During this topic you will come across the term of partial pressure of oxygen. It does not mean the pressure of the blood itself. Essentially it is a measure of the concentration of oxygen. It is written in shorthand as pO 2 and is measured in kilopascals ( kPa )

Note: During this topic you will come across the term of partial pressure of oxygen.

It does not mean the pressure of the blood itself.

Essentially it is a measure of the concentration of oxygen.

It is written in shorthand as pO 2 and is measured in kilopascals ( kPa )

Inhaled air in the alveoli has a p O 2 =14kPa. The p O 2 of resting tissue = 5.3kPa Lower p O 2 = lower O 2 concentration due to respiration and the p O 2 of active tissues = 2.7kPa. In either case, blood arriving at the lungs has a lower p O 2 than that in the lungs.

Inhaled air in the alveoli has a p O 2 =14kPa.

The p O 2 of resting tissue = 5.3kPa

Lower p O 2 = lower O 2 concentration due to respiration and the p O 2 of active tissues = 2.7kPa.

In either case, blood arriving at the lungs has a lower p O 2 than that in the lungs.

There is therefore a diffusion gradient and oxygen will move from the alveoli into the blood. The O 2 is then loaded onto the Hb until the blood is about 96% saturated with oxygen. The Hb is now called oxyhaemoglobin (Hb O 8 ). Hb + 4 O 2  Hb O 8

There is therefore a diffusion gradient and oxygen will move from the alveoli into the blood.

The O 2 is then loaded onto the Hb until the blood is about 96% saturated with oxygen. The Hb is now called oxyhaemoglobin (Hb O 8 ). Hb + 4 O 2  Hb O 8

Bohr shift Partial pressures of CO 2 also play a part in oxygen dissociation RBC cytoplasm contains enzyme carbonic anhydrase to combine CO 2 and H 2 0 to produce carbonic acid (H 2 CO 3 ) Carbonic acid then dissociates into Hydrogen ions and hydrogen carbonate ion Haemoglobin then combines with H ions to make HHB haemoglobinic acid and release oxygen

Partial pressures of CO 2 also play a part in oxygen dissociation

RBC cytoplasm contains enzyme carbonic anhydrase to combine CO 2 and H 2 0 to produce carbonic acid (H 2 CO 3 )

Carbonic acid then dissociates into Hydrogen ions and hydrogen carbonate ion

Haemoglobin then combines with H ions to make HHB haemoglobinic acid and release oxygen

Haemoglobin controls pH by mopping up the hydrogen ions The presence of CO 2 indirectly causes release of oxygen This is called the Bohr effect after German scientist Christian Bohr discovery in 1904

Haemoglobin controls pH by mopping up the hydrogen ions

The presence of CO 2 indirectly causes release of oxygen

This is called the Bohr effect after German scientist Christian Bohr discovery in 1904

Carrying oxygen in the blood Lesson 2 : Fetal haemoglobin, altitude and carbon monoxide

Lesson 2 : Fetal haemoglobin, altitude and carbon monoxide

Fetal haemoglobin Has a higher affinity for oxygen than mother’s haemoglobin So in the blood capillaries of the placenta where partial pressure of Oxygen is low Mothers blood gives up oxygen However fetal blood picks up the oxygen here.

Has a higher affinity for oxygen than mother’s haemoglobin

So in the blood capillaries of the placenta where partial pressure of Oxygen is low Mothers blood gives up oxygen

However fetal blood picks up the oxygen here.

Altitude Air pressure at sea level = 20KPa and Partial pressure of oxygen in lungs is 13KPa Therefore % saturation of haemoglobin =…… But at altitude ( up a mountain) air pressure = 10Kpa and in lungs = 5.3 KPa so saturation of haemoglobin =……….

Air pressure at sea level = 20KPa and Partial pressure of oxygen in lungs is 13KPa

Therefore % saturation of haemoglobin =……

But at altitude ( up a mountain) air pressure = 10Kpa and in lungs = 5.3 KPa so saturation of haemoglobin =……….

So what? Less O 2 round body Breathless Dizziness Weakness ALTITUDE SICKNESS Can be resolved by going back down

Less O 2 round body

Breathless

Dizziness

Weakness

ALTITUDE SICKNESS

Can be resolved by going back down

But if long term: Brain arterioles dilate More blood enters and loses fluid into the brain causing swelling Fluid also leaks into lungs However if it has a long time to adjust your body can adapt…..

Brain arterioles dilate

More blood enters and loses fluid into the brain causing swelling

Fluid also leaks into lungs

However if it has a long time to adjust your body can adapt…..

Adaptations After two- three weeks at altitude number of red blood cells increase In indigenous populations: Broader chests: greater lung capacity Larger heart (especially right side) More haemoglobin in blood

After two- three weeks at altitude number of red blood cells increase

In indigenous populations:

Broader chests: greater lung capacity

Larger heart (especially right side)

More haemoglobin in blood

Carbon Monoxide CO forms when carbon containing compound combusts without enough oxygen Combines with haemoglobin to form CARBOXYHAEMOGLOBIN Haemoglobin combines 250 times more readily with CO than O 2 Makes very stable compound Can easily kill (bright red dead body)

CO forms when carbon containing compound combusts without enough oxygen

Combines with haemoglobin to form CARBOXYHAEMOGLOBIN

Haemoglobin combines 250 times more readily with CO than O 2

Makes very stable compound

Can easily kill (bright red dead body)

Cigarette smoke contains 5% CO But also diluted with air 5% smokers blood permanently is combined with CO

Cigarette smoke contains 5% CO

But also diluted with air

5% smokers blood permanently is combined with CO