Haemoglobin

• Haemoglobin is a globular protein which is an oxygen-carrying pigment
• Red blood cells have a bio-concave shape this creates a high surface area to volume ratio for the t diffusion of gasses.
• Haemoglobin has a quaternary structure that consists of four polypeptide chains (two alpha-globins and two beta-globins) and each subunit has a haem group
• The globin subunits are held together by disulphide bonds
• If the sequence of amino acids changes it can change the function of the Haemoglobin
• The haem groups contain iron
• Each Haemoglobin has four haem groups so can carry 4 oxygens
• Oxygen is not very soluble in water
• The binding of the first oxygen causes a conformational change making it easier for the Haemoglobin to bind to other oxygens (cooperative binding)
• When oxygen binds with Haemoglobin it forms oxyhemoglobin
• The amount of oxygen combined with the Haemoglobin is known as the percentage saturation of the Haemoglobin
• Partial pressure is the amount of s particular gas in a mixture of gasses or a solution
• For the graph at the top oxygen has a high affinity for oxygen so loads oxygen at the lungs and then as the bottom of the graph the Haemoglobin has a low affinity for oxygen and a low partial pressure so unloads the oxygen at the cells.
• Loading is when oxygen is taken up by Haemoglobin (also known as associating)
• Unloading is when oxygen is released/given up by Haemoglobin (also known as disassociatio)
• Affinity is the ease with which haemoglobin binds and dissociates with oxygen
• unloading happens at a low concentration of oxygen
• Haemoglobin has a high affinity for oxygen at a high partial pressure oxygen
• Saturation of Haemoglobin happens at the pulmonary capillaries
• Increased respiration means the tissue respire quickly producing carbon dioxide this reduces the partial pressure of oxygen to a level lower than normal and so the Haemoglobin will become more dissociated (less saturated) therefore more oxygen will be released from the Haemoglobin
• In high concentrations of carbon dioxide the disassociating curve shifts to the right (outwards) meaning Haemoglobin affinity if oxygen has decreased so more oxygen is unloaded and more oxygen is available for respiration
• The dissociation curve shifts to the right for animals with a high metabolic rate and left for animals that live in areas of a low partial pressure (high altitude, bottom of lakes)
• The partial pressure of oxygen is the pressure exerted by oxygen within a mixture of gasses (it is a measure of oxygen concentration)
• Metabolism is all the chemical processes that take place in living organisms