4.5

• Structure of Haemoglobin:

  Globular, water soluble. Consists of four polypeptide chains, each carrying a haem group (quaternary structure)
• Describe the role of Haemoglobin

  • Present in red blood cells
  • Oxygen molecules bind to the haem groups and are carried around the body to where they are needed in respiring tissues
• How does partial pressure of oxygen affect oxygen-haemoglobin binding?

  As it increases, the affinity of haemoglobin for oxygen also increases, so oxygen binds tightly to haemoglobin. When partial pressure is low, oxygen is released from haemoglobin
• Explain the Bohr effect

  As partial pressure of carbon dioxide increases, the conditions become acidic causing haemoglobin to change shape. The affinity of haemoglobin for oxygen therefore decreases, so oxygen is released from haemoglobin
• What does Oxyhaemoglobin dissociation curves show?

  • Show saturation of haemoglobin with oxygen (in %), plotted against partial pressure of oxygen (in kPa). Curves further to the left show the haemoglobin has a higher affinity for oxygen
• How does the Bohr effect alter the position of an oxyhaemoglobin dissociation curve?

  Shifts the oxyhaemoglobin dissociation curve to the right because haemoglobin's affinity for oxygen has decreased
• How does Myoglobin differ from haemoglobin?

  • Only has one haem group
  • Has a very high affinity for oxygen even at low partial pressures
  • Is found in muscle cells of mammals with high metabolic demands
• Foetal haemoglobin


  • Has a higher affinity for oxygen than adult haemoglobin. Allows both mother's and child's oxygen needs to be met as the partial pressure of oxygen is low by the time it reaches the foetus
• How does fetal haemoglobin different adult haemoglobin?

  The partial pressure of oxygen and is low by the time it reaches the foetus, therefore foetal haemoglobin has a higher affinity for oxygen than adult. Allows both mother‘s and child’s oxygen needs to be met
• Structure of haemoglobin:

  Haemoglobin is awards so both globular protein which consist of four polypeptide chains, 2 alpha and 2 beta, as well as a haem group. Carries oxygen in the blood is oxygen combined to the haem (Fe2+) grout and oxygen is then released when acquired. Each Hb molecule can carry 4 oxygen molecules
• How does oxygen bind to haemoglobin?

  Each haemoglobin is made up of 4 subunits (haem groups) each containing an iron ion, and this is the bind point for oxygen.
• Describe the structure of haemoglobin

  • Haemoglobin is a globular protein
  • Have four haem (prosthetic) groups containing an iron ion each
• How does an oxygen molecule bind to each iron ion?

  Via a covalent bond
• What does the Bohr effect describe?

  It describes the decrease in the oxygen affinity to haemoglobin in the presence of low pH or high CO2 (in relation to pH and carbon dioxide levels).