Question

when electrons flow along the electron transport chains of mitochondria, the pH of matrix increases. why?

Answer 1

high pH = low H+ concentration
low pH = high H+ concentration

the pH of the matrix increases because protons (H+) from the matrix are pumped across the inner mitochondrial membrane into the inter membrane space resulting in a decrease in H+ concentration in the matrix.The constant pumping of H+ ion from the matrix into the inter membrane space results in a higher H+ concentration (low pH) in the inter membrane space and lower H+ concentration ( high pH) in the matrix thus creating a proton gradient / electrochemical gradient. This proton gradient serves a very important function ie of ATP synthesis. As H+ ions move down the concentration gradient from the inter membrane space into the matrix the energy stored in the electrochemical gradient is dissipated which is used for ATP synthesis. So the energy of the electrochemical gradient is now stored in the phosphoanhydride bonds of ATP which when cleaved release energy that can be utilized to carry out cellular processes.