Transport of oxygen and carbon dioxide — common mistakes

Remember, a 'right shift' of the oxygen dissociation curve means a reduced affinity of haemoglobin for oxygen, leading to more oxygen being released to the tissues. Think 'R' for Right, 'R' for Reduced affinity, 'R' for Released!

Oxygen is primarily transported in the blood bound to haemoglobin within red blood cells, forming oxyhaemoglobin. A small amount also dissolves directly in the plasma. To master this and other key biology topics, check out our free premium revision course and extensive past paper collection for Cambridge 9700.

The Bohr effect describes how an increase in carbon dioxide concentration, lower pH, and higher temperature reduce haemoglobin's affinity for oxygen, shifting the oxygen dissociation curve to the right. This is vital because it ensures oxygen is released more readily to active tissues that need it most, such as working muscles, for efficient aerobic respiration.

The majority of carbon dioxide (about 70%) is transported in the blood plasma as hydrogencarbonate ions (HCO₃⁻). Another 20% binds to haemoglobin as carbaminohaemoglobin, and the remaining 10% is dissolved directly in the plasma. Understanding this process, including the crucial chloride shift, is key for your Cambridge 9700 Biology exams.