The two power point slides in this activity illustrate gas exchange in the lungs (external respiration) tissues (internal respiration). Each slide shows a cell (either tissue cell or alveolar cell) at the top and a blood vessel (with plasma and RBC) below. To complete the activity: 1. Determine which illustration is external respiration and which is internal respiration. You must do this first so that you wil use the correct description to label each slide. 2. On each slide, drag the cell name (either tissue cell or alveolus) onto the cell at the top. 3. Read the descriptions below, one for external respiration and one for internal respiration, and as you do, drag the numbers on each slide to their correct location on the illustration. External respiration During external respiration, the small amount of carbon dioxide transported in the plasma (1) quickly diffuses out of the blood down its pressure gradient. A small amount of oxygen (2) dissolves in the plasma. However, a majority of the oxygen continues into the red blood cell (3), where it combines with deoxyhemoglobin (4) to form oxyhemoglobin (5), releasing a hydrogen ion (6). When hemoglobin is saturated with oxygen, its affinity for carbon dioxide decreases. Carbon dioxide combined with hemoglobin (7) dissociates and diffuses out of the red blood cell (8), and out of the plasma. Thus, oxygen loading facilitates carbon dioxide unloading from hemoglobin. This interaction is called the Haldane effect. • The hydrogen ion released from hemoglobin (step 6) combines with a bicarbonate ion (9), which diffuses into the red blood cell from plasma in exchange for a chloride ion (10). This exchange is referred to as the chloride shift. The reaction between hydrogen and bicarbonate ions forms carbonic acid (11). • Carbonic acid breaks down into water and carbon dioxide (12), catalyzed by the enzyme carbonic anhydrase. The water produced by this reaction may leave the red blood cell, or remain as part of the cytoplasm. The carbon dioxide diffuses out of the red blood cell (13) into the plasma and out of the blood. TISSUE CELL ( CO: CO: O2 ALVEOLUS plasma 1 CO: red blood 8 cell 9. CO: CO2 + Hb HBCO2 4 10 5 11 O2 + HHb+ HbO2 + H* 6 12 CO: carbonic anhydrase CO + H20" H2CO3 • H* + HCO, HCO;- 7. 2. 3.