What is a Protocell?

Formed from the aggregation of abiotic components, protocells are the precursors to modern living cells. Despite being non-living, protocells display characteristics akin to biological cells.

Fatty acids forming a protocell - Tomasz SwierczynskImage Credit: Tomasz Swierczynsk / Shutterstock

Understanding the origins of life on earth

Life on Earth would not be possible without the abiotic building blocks which facilitated its development. Though it has not been fully elucidated, the culmination of various chemical, prebiotic evolutionary changes gave rise to living cells. To understand this, it is essential to understand what a living system is.

Living beings generally display three common functionalities:

  • A stable and semi-permeable membrane which encapsulated cell components
  • Genetic material which can be passed on and controls cellular behavior and function
  • Energy generation via metabolic pathways which enables growth, self-maintenance, and reproduction

Formation of protocell

A research group at the University of Harvard lead by Nobel Prize winner, Jack Szostak, were the pioneers to demonstrate a transition between abiotic and living materials in a laboratory setting.

The group developed what is known as the protocell which is a spherical, autonomous, cell-like structure exhibiting the aforementioned traits.

Producing the first protocell

Szostak and his colleagues developed the protocell by putting fatty acids into water.

Fatty acids have hydrophilic polar ends and hydrophobic tails and when introduced to an aqueous environment, the fatty acids take on a rounded shape with the hydrophilic tails pointing outward and the hydrophilic ends pointing inward. If a water molecule is trapped within the fatty acid, it causes instability.

To circumvent this issue, a lipid bilayer is formed with hydrophobic polar ends facing both inward and outward and hydrophilic tails sandwiched between the polarised ends.

While DNA and RNA are unable to pass through the bilayer of protocells, nucleic acids can. They can also replicate within the structure. Through the study of protocells, a clearer image can be drawn in relation to the origin of life on Earth and the connections between abiotic and living materials can be fully elucidated.

Top-down vs. the bottom up approach

The development of artificial cell types like protocells have potential applications in medicine, biotechnology, and drug delivery and shed light on the evolutionary changes that have taken place over the course of history. There are two main methods by which artificial cells can be produced; the top-down method and the bottom-up method.

The top-down approach

The top-down approach creates artificial cells through the simplification of a cell’s genomic information. The removal of genes forms a minimal cell that has enough genomic material within it to enable self-maintenance and reproduction. Minimal cells present the opportunity to insert new genes into cells and modify them for purpose.

The bottom-up approach

The bottom-up approach presents more challenges than the top-down approach. Rather than stripping cells of genes, the method produces artificial cells from its molecular constituents. In spite of this, the bottom-up approach more closely resembles how cells were created at the initial stages of life on Earth.

These approaches to producing artificial cells have their own distinct characteristics, they work hand in hand to produce artificial cells - ultimately aiding the advancement of biomedical and biotechnological research.

An artificial approach to understanding life and enhancing bioscience

The engineering of artificial cells like protocells is of huge interest to researchers in various fields. Not only can the study of these artificial cells enhance our understanding of evolutionary processes, but they have the potential to enhance drug delivery, biotechnology, and medicine.

Further Reading

Last Updated: Oct 12, 2018

Maryam Mahdi

Written by

Maryam Mahdi

Maryam is a science writer with a passion for travel. She graduated in 2012 with a degree in Biomedical Sciences (B.Sc.) from the University of Manchester. Maryam previously worked in scientific education and has produced articles, videos, and presentations to highlight the association between dietary choices and cancer. She produces a range of articles for News-Medical, with a focus on microbiology and microscopy.

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