A chemical conundrum complicates researchers’ understanding of how the first biological cells emerged. Those protocells were most likely formed from fatty acid vesicles serving as membranes. Some researchers have suggested that vesicles, proteins and RNA all formed separately and later joined to make protocells. But while the chemical reactions needed to make proteins and RNA would have relied on salty water and metal ions, those conditions make fatty acid vesicles break apart. Researchers at the University of Washington led by Sarah L. Keller have an explanation. They propose that two components of protocells—their membranes and proteins—cooperated to make them stable even in the presence of ions, potentially enabling protocell protein synthesis (Proc. Natl. Acad. Sci. U.S.A. 2019, DOI: 10.1073/pnas.1900275116). Keller’s team found that when they made protocell-like lipid vesicles in the presence of hydrophilic amino acids such as serine, the cells were stable and didn’t fall apart in salty conditions. Keller says this lends support to the idea that protocells could not have been formed by some union of independently produced lipid membranes, RNA, and proteins. Instead, the researchers suggest that life may have begun when protocells bound and concentrated the building blocks of proteins and RNA, allowing life’s reactions to begin.