Ada Yonath, the boundary-pushing Israeli chemist whose ingenuity and tenacity helped unlock the inner workings of the ribosome — the microscopic factory inside every living cell that builds the proteins necessary for life — died on August 31. She was 87. The Weizmann Institute of Science, near Tel Aviv, where Dr. Yonath worked for decades, announced her death.

            Dr. Yonath’s career was defined by a question that had long bedeviled scientists: What does the ribosome actually look like? Determining its three-dimensional structure at the molecular level was considered one of biology’s most elusive challenges.

            Although progress was slow, by the 1980s and ‘90s, her laboratory began producing increasingly detailed images of the ribosome. Around the same time, two other researchers entered the field. All three of their efforts culminated in the first high-resolution images of the ribosome’s structure. For this achievement, they shared the Nobel Prize in Chemistry. In announcing the award, the Nobel committee highlighted their roles in clarifying “fundamental and medically important aspects of ribosome function” that led to “the development of novel antibiotic drugs in the ongoing medical struggle against the ever-emerging drug resistance among bacterial pathogens.”

            Chosen to deliver the Nobel acceptance speech because of her resolve and pioneering methodology, Dr. Yonath said that the earliest inspiration for her research came from the polar bear. “Polar bears pack their ribosomes in an orderly way in their cells just before hibernation,” she said, “and these stay intact and functional for months. I said: ‘If polar bears know how to do it, we can do it, too.’”