L INK BETWEEN THE STRUCTURE & FUNCTION OF HAEMOGLOBIN, MYOGLOBIN, LEUCOCYTES AND PLATELETS

H AEMOGLOBIN Where is haemoglobin found? …………………….. It consists of 4 coiled polypeptide chains known as globins which are each attached to an iron containing molecule called haem. Oxygen is transported when it combines with the haem forming oxy- haemoglobin.

S TRUCTURE OF A HAEM A haem consists of 4 polypeptide chains and a central iron atom When oxygen is taken up by haemoglobin, it is known as oxygenation. What is the difference between oxygenation and oxidation?

O XYGENATION Haemoglobin (Hb) + O2 reacts to form oxy- haemoglobin This is a reversible reaction Hb + O2 reacts to form Hb02 (oxy-haemoglobin) This is the main way in which O2 is transported in the blood as very little O2 dissolves in blood plasma

P ARTIAL AND FULLY SATURATED HAEM MOLECULES Since each haemoglobin molecules contains 4 haem groups ie 4 iron molecules, each molecule of haemoglobin can carry 4 oxygen (O2) molecules ie Hb + 4O2 = HbO8 (fully saturated haemoglobin Write the equation for a haemoglobin molecule carrying 2 or 3 oxygen (O2) molecules? Are they fully saturated?

T RANSPORT OF CO2 Carbon dioxide is transported by the blood in 3 ways 1. CO2 is more soluble than O2, so up to 5% of CO2 can be transported in the plasma 2. CO2 combines with the amino groups in haemoglobin forming carbamino-haemoglobin. This is a reversible reaction

T RANSPORT OF CO2 2. CO2 also combines with the amino groups of plasma proteins About 10% of the CO2 is transported in combination with amino groups

T RANSPORT OF CO2 3. Most of the CO2 is transported as bicarbonate ions. CO2 diffuses into red blood cells and combines with water to form carbonic acid (H2CO3). The enzyme carbonic anhydrase catalyses this reaction. Carbonic acid then dissociates to form bicarbonate ions (HCO 3 - ) and hydrogen ions (H + ).

T RANSPORT OF CO2 Most of the CO2 is transported as bicarbonate ions. CO2 diffuses into red blood cells and combines with water to form carbonic acid (H2CO3). The enzyme carbonic anhydrase catalyses this reaction. Carbonic acid then dissociates to form bicarbonate ions (HCO 3 - ) and hydrogen ions (H + ).

CO2 EXCHANGE IN THE LUNGS In the lungs bicarbonate ions diffuse into the red blood cells and combine with hydrogen ions to form carbonic acid. This is broken down into carbon dioxide and water. Carbon dioxide diffuses out of the red blood cells and into the alveoli.

M YOGLOBIN Myoglobin (Mb) is a protein containing a haem. It is the primary oxygen - carrying pigment of muscle tissues. It carries oxygen as oxy-myoglobin and when it releases its oxygen, it is called deoxy-myoglobin

M YOGLOBIN High concentrations of myoglobin in muscle cells allow organisms such as whales and seals to hold their breaths longer. Myoglobin is only found in the blood when a muscle injury has occurred.