system
Given the following post, respond as if you're commenting on Reddit:
human
Why does ingesting lead cause poisoning and ingesting silver or gold does not? What is it about lead that makes it toxic?
gpt
Lead gets mistaken for other +2 ions such as iron or calcium.  In the case of iron it can interfere with iron transport through binding to cysteine (lead has higher affinity for thiolates than iron), and heme synthesis (lead doesn't participate in the same electron transfer chemistry as iron). In the case of calcium, it interferes with neuron potentiation by binding tightly to an enzyme normally associated with calcium ion transport. Lead is usually ingested as an ion due to decomposition of pipes or as an inorganic salt component in paint (when leaded gasoline was still used, it was inhaled as lead oxide dust). Metallic lead isn't that toxic (otherwise folks with bullet's lodged in them would be in serious trouble) as the surface forms a passivating lead oxide layer that is stable at physiological pH.

Silver and gold are normally encounterd as metals.  The do not dissolve to appreciable extent in the GI tract as they are non-reactive. Silver ions CAN lead to some interesting effect (including turning a person blue) if ingested in significant quantity. Gold ions actually can be toxic, but gold salts are almost never encountered outside of metal mining/refining.