Protocells are artificial or natural structures that resemble cells but lack some essential characteristics of living cells. They are often used in scientific research to study the origins of life, cell evolution, and the minimal requirements for life.

Protocells can be:

1. Artificially created: Scientists design and assemble protocells using various materials, such as lipids, polymers, or other molecules, to mimic cellular structures and functions.
2. Naturally occurring: Some natural structures, like liposomes or membranous vesicles, can be considered protocells due to their cell-like properties.

Protocells typically possess some, but not all, of the following characteristics:

· Membrane-bound structure
· Selective permeability
· Metabolic processes (e.g., chemical reactions)
· Replication or self-assembly
· Response to environmental stimuli

However, protocells usually lack:

· Genetic material (DNA or RNA)
· Complex cellular organization
· True cellular metabolism
· Evolutionary capabilities

By studying protocells, researchers aim to understand the fundamental principles of life, the emergence of cellular complexity, and the possibility of life existing elsewhere in the universe.