External and Internal Respiration

Learning Outcomes: C10 – Analyse internal and external respiration –State location –Describe conditions (ph, temperature) –Describe roles of oxyhemoglobin, carbaminohemoglobin, reduced hemoglobin, bicarbonate ions, carbonic anydrase –Write Chemical equations for external and internal respiration

Review – 4 Levels of respiration Breathing External respiration- in the lungs (what gas exchange occurs here?) Internal respiration - in the tissues (what gas exchange occurs here?) Cellular respiration - in the mitochondria of cells (what is used and produced?)

Fig. 15.8

Fig. 15.4

Fig

1. External (lungs): O 2 O 2 diffuses from the alveoli into the blood (why?) What molecule in the blood does O 2 bind to? O 2 binds to hemoglobin to form oxyhemoglobin Hb + O 2 HbO 2

Binding of O 2 to hemoglobin occurs best at lower temperature, higher pH and higher P O2 (oxygen pressure) of the lungs

Fig. 15.9

2. Internal (tissues): O 2 O 2 dissociates from Hb, leaving deoxyhemoglobin HbO 2 Hb + O 2 Bond is weaker due to higher temperature, lower pH and lower P O2 O 2 diffuses into tissue fluid and cells, where it is used for cellular respiration

3. Internal (tissues): CO 2 What process produces CO 2 ? CO 2 is produced by cellular respiration in all cells CO 2 diffuses out of cells into tissue fluid, and then into capillaries A small amount combines with Hb to form carbaminohemoglobin Hb + CO 2 Hb CO 2

Most CO 2 combines with H 2 O to form carbonic acid, which dissociates to form hydrogen ions and bicarbonate ions: CO 2 + H 2 O H 2 CO 3 H + + HCO 3 - This reaction is catalyzed by the enzyme carbonic anhydrase (found in red blood cells)

HCO 3 - is carried in the plasma H + is picked up by hemoglobin, forming reduced hemoglobin: H + + Hb HHb This prevents too much acidity in the blood

4. External (lungs): CO 2 Bicarbonate ions release CO 2 : H + + HCO 3 - H 2 CO 3 H 2 O + CO 2 Carbaminohemoglobin releases CO 2 CO 2 diffuses out of the capillaries into the alveoli, to be breathed out