This is due to the fact that water has high specific heath capacity,which makes it to accommodate large amount of heat energy produced by the catabolic reactions which liberated heat.
General, the amount of heat energy needed to raise the temperature of a particular substance over a given amount is called the specific heat capacity of that substance. Therefore for water, the amount of heat energy needed to raise the mass of 1kg of water by 1 degree is called the specific heat capacity of water.
Since large hydrogen bonds held water molecules together,it takes a long time of heat energy to break these bonds free to raise the temperature of water.Hence, water in living cells is able to accommodate large amount of heat energy to stabilise the temperate of the cells.
They are considered to have originated from cyanobacteria through endosymbiosis—when a eukaryotic cell engulfed a photosynthesizing cyanobacterium that became a permanent resident in the cell
