Temperature and pH can have profound effects on the ionization states of molecul

I believe the temperature can destroy the molecule, not too sure about this one. 

Then maybe I can help: Okay, so molecules are frequently connected to each other via weaker or less stable bonds. The ionization state of molecules frequently is dependent upon weaker bonds. Generally, lower temperatures make bonds more stable, and higher temperatures destabilize the bonds by decreasing or increasing molecular movements. pH also changes bond strength by changing the concentration of hydrogen ions available to interact with molecules. Changes in ionization of proteins can change their folding, and therefore their function. Since proteins are integral to cell performance, disrupting their functionality will also disrupt normal processes in cells, causing possible harm to the organism.