A base is any substance that accepts hydrogen ions when dissolved in water. They are called alkaline. The ph scale measure the concentration of hydrogen ions. A ph above 7 is basic and below is acid. 7 is neutral.
Buffers moderate the changes in ph.
This helps keep equilibrium in the body. The H2CO3 acts as a hydrogen donor. It dissociates the hydrogen ion and carbonate ion. The carbonate ion resists change by soaking up the acid or base. This is the hydrogen acceptor.