He graduated from the Royal Technical College of Charlottenburg in 1904.
He became a Soviet activist after the annexation of Western Ukraine in 1939, but he was murdered during the Stalinist Doctors' Plot purge in 1949. From 1920 to 1941, he was head of the Institute of the Medical Chemistry at Lviv University. He traveled across Europe, collaborating with universities in Cambridge, Naples, Strasbourg, Ghent and Zurich.
After the Soviet invasion of Poland and annexation of Western Ukraine in 1939 by the Soviet Union, Parnas remained in Lviv to continue his work in the institute. He also started collaborating with the Soviet authorities by taking on a political role in the communist District Soviet Worker's Delegation. In 1941, after the German invasion of the Soviet Union, Parnas was evacuated deeper into the USSR and remained there for the rest of his life.
Only a few days after his departure Lviv was occupied by the Nazi Germany army, who massacred approximately 45 Lwów professors. In the Soviet Union, Parnas met Joseph Stalin, and received his own laboratory. According to KGB's archives, he died during his first interrogation at Lubyanka prison "from a heart attack" on January 29, 1949.
Parnas is honored by the Polish–Ukrainian Parnas Conference organized by the Polish and Ukrainian Biochemical Societies, which has been held every two years since 1996.
[Academy of Sciences of the USSR]
He was a member of the German Academy of Sciences Leopoldina, Corresponding Member of the Polish Academy of Sciences, as well an honorary doctor of Sorbonne University and the University of Athens. He became an Academician of the Academy of Sciences of the USSR and a founding member of the Academy of Medical Sciences of the USSR.