Final answer:
Protocells are considered early precursors to living cells, consisting of spheres with lipid membranes that could concentrate solutes and support simple metabolic reactions, contributing to the evolution of cellular life.
Step-by-step explanation:
Protocells are spheres with lipid membranes that concentrate solutes and can even carry out simple metabolic reactions if provided with enzymes. They are considered to be an important step in the evolution of cellular life, arising after organic chemical prerequisites of life began to display familiar metabolic functions.
A protocell is a self-assembled, semipermeable structure that may have led to the first life forms. Though not living themselves, protocells could sequester biochemistries conducive to life, a hypothesis supported by the potential of certain protocell models, such as coacervates and liposomes, to replicate or at least perform some of the functions of life when exposed to the appropriate conditions.
The development into complex cells likely involved the evolution of simpler protocells, which over time also evolved into more complex structures as other organic compounds such as DNA and proteins developed, providing the stability and genetic transmission necessary for life.