CI- 3 Na' Questions Base - 2K. 1. What enzyme catalyzes the formation of H CO from CO and HaO? (This enzyme also catalyzes the formation of H O and CO from H CO .) 2. The diagram above (Figure I) outlines the mechanism by which He is actively secreted into the PCT of the kidney nephron. What other substances must be transported from the tubular fluid into the PCT cell (across the apical or luminal membrane) or from the PCT cell into the interstitial fluid (across the basolateral membrane) as part of the transport of the H.? 3. What would happen to the amount of H. secreted into the renal tubule if the activity of the Na /K. ATPase were increased? Are there diseases or other conditions that might enhance the activity of this sodium pump