QuestionSBA
QuestionChoice
Whilst stomach acid is HCl, H<sup>+</sup> and Cl<sup>-</sup> do not combine until inside the stomach lumen where they combine due to their differing charges. Cl<sup>-</sup> enters the stomach lumen via a Cl<sup>-</sup> channel in exchange for the HCO<sub>3</sub> <sup>-</sup> produced by the reaction CO<sub>2</sub> + H<sub>2</sub>O &rarr; H<sub>2</sub>CO<sub>3</sub> &rarr; HCO<sub>3</sub><sup>-</sup> in the gastric parietal cells (which is catalysed by carbonic anhydrase!)
10000498
c
2Cl<sup>-</sup> + H<sub>2</sub>O &rarr; HCl + OH<sup>-</sup>
QuestionChoice
This is the equation for the formation of calcium oxalate kidney stones, and whilst it does produce acidic H<sup>+</sup> ions, it has no link to stomach acidity.
10000500
e
Ca<sup>2+</sup> + C<sub>2</sub>O<sub>4</sub>H<sub>2</sub> &rarr; CaC<sub>2</sub>O<sub>4</sub> + 2H<sup>+</sup>
QuestionChoice
This reaction is catalysed by carbonic anhydrase and is used for homeostasis in many systems, including within gastric parietal cells - causing them to secrete acidic H<sup>+</sup> into the stomach, thus decreasing the stomach pH.
10000496
a
CO<sub>2</sub> + H<sub>2</sub>O &rarr; H<sub>2</sub>CO<sub>3</sub> &rarr; H<sup>+</sup>+ HCO<sup>3</sup> <sup>-</sup>
QuestionChoice
H+ is produced by this reaction, so would decrease the stomach pH. However, the equation is not balanced in charge or molecules - there are two hydrogens on the left and three on the right, and the total charge on the left is 0, whilst it is +1 on the right.
10000497
b
CO<sub>2</sub> + H<sub>2</sub>O&rarr; 2H<sup>+</sup>+ HCO<sub>3</sub> <sup>-</sup>
QuestionChoice
This reaction is the reversed version of the reaction which occurs within gastric parietal cells to produce H<sup>+</sup> and decrease the stomach pH, and whilst this reaction is also catalysed by carbonic anhydrase it is a neutralising reaction, rather than an acid-producing reaction, so if anything would increase the pH.
10000499
d
HCO<sub>3</sub><sup>-</sup> + H<sup>+</sup> &rarr; H<sub>2</sub>CO<sub>3</sub> &rarr; H<sub>2</sub>O + CO<sub>2</sub>
Concept
Chapter
2693
3776
Gastric Secretion
Topic
149
Gastro-intestinal physiology
12646
Which of the following reactions is catalysed by the enzyme carbonic anhydrase within gastric parietal cells in order to decrease the pH of the stomach?
a