Haemoglobin

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Haemoglobin is a protein fouund in red bllod cells which has the capability to transport 4 molecules of oxygen.

It is made up of four polypeptide chains each with one haem group.

Partial pressure of oxygen is a measure of the concentration of oxygen

Oxyhaemoglobin created from loading of oxygen in lungs

Hb + 4O2 -> HbO8

Dissociation curves

It is S-shaped because of the behaviour of the Hb in different pO2.

The first molecule of O2 that connects is difficult and slow but this molecule slightly distorts the shape of the haemoglobin. This makes it easier for the other O2 molecules to bind to the haem groups.The last O2 to join is also difficult because there is a shallow concentration gradient, nearly fully saturated.

The effect of pH - The Bohr Effect

An acidic environment means more dissociation so O2 is released to the tissues.

Dependent on the concentration of hydrogen ions in blood.

H+ displaces O2 from Hb leaving

HbO2 + H+ -> HHb + O2.

Hb acts as a buffer to maintain the neutral conditions of the blood.

Carbon dioxide on the Dissociation Curve

HAEMOGLOBIN

The more CO2 the more the curve shifts to the right.

Carbonic anhydrase enzyme catalyses the reaction between CO2 and H20 dissociating into HCO3- and H+. Meaning the more CO2 the more acidic the blood so greater dissociation.

Carbon monoxide creates carboxyhaemoglobin and this prevents the Hb from binding with the O2 molecules.

Foetal haemoglobin has a higher affinity for O2 to allow more oxygen to load more easily to make sure the foetus gets enough O2. It gets its oxygen from the mother's blood which already has a lower concentration gradient. Thherefore to maximise oxygen the curve shifts to the left;

Myoglobin is a pigment in skeletal muscle that has a higher affinity for 02 than Hb. As the Hb unloads the myoglobin loads O2 easily.

It stores the O2 until it is required, when Hb can't supply enough O2 to meet demand.

Curve shifts to the left.

Higher the temperature the less saturation of the blood with 02.

Oxygen supply needs to increase because of the increase in metabolic activity. It needs to dissociate O2 more quickly to the surrounding tissues.

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