Complex sentence: The flesh of a Greenland shark is poisonous due to the presence of the toxin trimethylamine oxide which, upon digestion, breaks down into trimethylamine, producing effects similar to extreme drunkenness.
Split into simpler sentences: The flesh of a Greenland shark is poisonous. This is due to the presence of the toxin trimethylamine oxide, which, upon digestion, breaks down into trimethylamine, producing effects similar to extreme drunkenness.