Yoshinori Ohsumi, a Japanese cell biologist, was awarded the Nobel Prize in Physiology or Medicine on Monday for his discoveries on how cells recycle their content, a process known as autophagy, a Greek term for “self-eating.”

It is a crucial process. During starvation, cells break down proteins and nonessential components and reuse them for energy. Cells also use autophagy to destroy invading viruses and bacteria, sending them off for recycling. And cells use autophagy to get rid of damaged structures. The process is thought to go awry in cancer, infectious diseases, immunological diseases and neurodegenerative disorders. Disruptions in autophagy are also thought to play a role in aging.

But little was known about how autophagy happens, what genes were involved, or its role in disease and normal development until Dr. Ohsumi began studying the process in baker’s yeast.

Why did he win?

The process he studies is critical for cells to survive and to stay healthy. The autophagy genes and the metabolic pathways he discovered in yeast are used by higher organisms, including humans. And mutations in those genes can cause disease. His work led to a new field and inspired hundreds of researchers around the world to study the process and opened a new area of inquiry.