Question

To what extent does the intracellular pH or the red blood cell vary during its movement from the tissues to the lungs and back, and why is this so?

Answer 1

If the carbon dioxide produced in cellular respiration accumulated within the cells, the pH of the cells would fall, hence making them more acidic, eventually resulting in death. The normal pH of tissue cells is about 7.4. This is the pH at which nerve cells best operate and cellular enzymes act to control cellular metabolism. Carbon dioxide diffuses down a concentration gradient in the same manner as oxygen. Blood entering the tissue capillaries carries Carbon dioxide at low levels. Blood leaving the tissue capillaries has a higher level. Carbon dioxide leaves the blood and diffuses down the concentration gradient across the capillary and alveoli walls. Blood leaving the lung capillaries has low levels of CO2. Low amounts of carbon dioxide can be carried in the blood due to its low solubility. Carbon dioxide diffuses into blood in tissue capillaries from surrounding cells and most enters the red blood cells. About seven per cent remains dissolved in the plasma and istransported back to the lungs in that form. Within red blood cells the following reaction occurs: The bicarbonate ions are very soluble and diffuse from the red blood cell into the blood plasma. The CO2 that remains in the red blood cells combines with the haemoglobin. So blood carries carbon dioxide from body tissues to lungs in three forms: bicarbonate ions, in the haemoglobin or dissolved in plasma. In lung capillaries the processes that occur with relation to carbon dioxide are the reverse of what occur in the blood.