Team:Santa Clara/NatureSolution
Nature's Solution
Nature employs numerous systems in order to cope with acidic conditions. These systems will work to actively transport or quench intracellular protons, increase the cell’s ability to repair from acid damage, alkalize the environment or alter its membrane composition to decrease its permeability to acid.
Glutamic Acid Decarboxylase system uses the conversion of glutamic acid to GABA with the uptake of a proton in order to decrease intracellular acid levels.
Proton Pumps
The most straight forward approach for the cell to attempt to remove the excess acid that has entered the cell. This active transport can work directly on protons, as in the F1FO ATPase, or it can expel intermediates that are formed during the uptake of a free proton, as in the GAD system.
F1FO ATPase used to actively transport protons out of the cytosol.
Protection and Repair of Macromolecules
pH levels below the physiological range are harmful to cells because they begin to damage major components that are essential to its vitality. Excess proton concentrations will begin to protonate nucleotide bases which leads to a break in the glycosyl bond and DNA damage. To offset the damage, AP (apurinic-apyrimidinic) endonucleases are then expressed to begin the multistep process to replace the missing bases. Similar to DNA, proteins become damaged by high acidity as they begin to denature. A myriad of proteins are then expressed to either refold the protein or tagging it for degradation/evacuation.
Image depicting the adaptation to alter the fatty acid profile of the lipid bilayer to include longer fatty acid chains to increase the thickness of the membrane.
Cell Membrane Changes
The significance of the changes to the cell membrane correspond directly to alterations in the fatty acid profile of the membrane. These alterations work to either increase the density or the thickness of the cell membrane in order to decrease its permeability to acid.
Production of Alkali
Cells also work to alkalinize the environment. They do so by using nitrogen, in the form of ammonia, to uptake free protons. The production of ammonia can result from either the break down of arginine to ornithine, or urea to carbon dioxide.
Ornithine/Arginine antiporter leading to the alkalization of the surrounding media.