Arsenic binds to sulfhydryl groups of many proteins with various toxic
effects. It may, for example, weaken the integrity of structural proteins, or
partially inactivate some enzymes. The severity of arsenic compound toxicity
also relates to energy metabolism. Kreb's cycle, for example, produces 90% of
biochemical energy used by the body. Arsenic compounds (arsenates) interrupt
this process with fatal consequences.
Arsenates also resemble phosphates in chemical behavior (arsenic and
phosphorus are in the same family of the Periodic Table). Thus, arsenates can
replace phosphorus in several process such as glycolysis, and no ATP is formed.
The ability of arsenic to behave like phosphorus also leads to storage of
arsenate in bone, a location in which it may accumulate in a stable manner for a
very long period of time.