Question

Cells in the wall of the mammalian stomach secrete HCI at a concentration of 0.15 M. The secreted protons, which are derived from the intracellular hydration of $\mathit{C}{\mathit{O}}_{\mathbf{2}}$by carbonic anhydrase, are pumped out by an $\left(H^{+}-K^{+}\right)\mathbf{-}\mathit{A}\mathit{T}\mathit{P}$antiport. A co-transporter is also required to complete the overall transport process.

a) Calculate the pH of the secreted HCl. How does this compare to the cytosolic pH (7.4)?

b) Write the reaction catalyzed by carbonic anhydrase.

c) Draw a diagram to show how the action of both transport proteins results in the secretion of HCI.

Short answer

In the solution (a), the pH of the secreted HCl is 0.822.

In the solution (b), the reaction is given as carbonic anhydrase.

In the solution (c), the diagram represents the antiport system is,

Step-by-step solution

Membrane proteins

The proteins which interacts with biological membrane and ions present at cell membrane can be considered as Membrane proteins. Transporter proteins and membrane receptor proteinsare the two main categories of membrane proteins. The proteins that carry chemicals and ions across the membrane are known as transporter proteins.

The negative logarithm of a solution's hydrogen ion concentration is used to calculate the pH of that solution. As the concentration of $H^{+}$ion grows in a solution, the pH falls.

In the solution (a), the value of secreted pH

Calculating the pH,

$$\begin{gathered} \text{pH = - log}\left[{\text{H}}^{\text{+}}\right] \\ \text{= - log}\left[\text{0.15}\right] \\ \text{= 0.822} \end{gathered}$$

In the solution (b), Reaction is catalysed by carbonic anhydrase

Carbonic anhydrase is an enzyme that catalyzes the interconversion process that takes place between carbon dioxide and water. In compared to other enzymes, carbonic anhydrase has an extremely quick reaction rate. The rate of reaction is determined by the rate ofsubstrate diffusion.

In the solution (c), Pictorial representation of (H+-K+)ATP ase Antiport system

As a result, the pH of the HCl produced is 0.822. Carbonic anhydrase is the name of the reaction. Theantiport systemis seen in the diagram.