fig2
![The complex relationship between multiple drug resistance and the tumor pH gradient: a review](https://image.oaes.cc/a50d708f-0e52-432a-88fd-862a8d692683/4680.fig.2.jpg)
Figure 2. CO2 of metabolic origin diffuses to the cell surface where it is hydrated to carbonic acid, which spontaneously ionizes to form a proton and a bicarbonate molecule. While the bicarbonate is reintroduced into the cell by NBC, the proton remains in the extracellular matrix, contributing to its acidification. NBC: Sodium-bicarbonate cotransporter.