Protobiont
Encyclopedia
Protobionts are systems that are considered to have possibly been the precursors to prokaryotic cells. If RNA
RNA
Ribonucleic acid , or RNA, is one of the three major macromolecules that are essential for all known forms of life....

 is trapped inside, the system can use the RNA or select for it.

A protobiont is an aggregate of abiotically produced
Abiogenesis
Abiogenesis or biopoesis is the study of how biological life arises from inorganic matter through natural processes, and the method by which life on Earth arose...

 organic molecules surrounded by a membrane or a membrane-like structure. Protobionts exhibit some of the properties associated with life
Life
Life is a characteristic that distinguishes objects that have signaling and self-sustaining processes from those that do not, either because such functions have ceased , or else because they lack such functions and are classified as inanimate...

, including simple reproduction, metabolism
Metabolism
Metabolism is the set of chemical reactions that happen in the cells of living organisms to sustain life. These processes allow organisms to grow and reproduce, maintain their structures, and respond to their environments. Metabolism is usually divided into two categories...

 and excitability, as well as the maintenance of an internal chemical environment different from that of their surroundings. It has been suggested that they are a key step in the origin of life on earth. Experiments by Sidney W. Fox
Sidney W. Fox
Sidney Walter Fox was a Los Angeles-born biochemist responsible for unique discoveries in the autosynthesis of protocells.-Professor:In 1943 Fox was granted his first academic position at Iowa State College....

 and Aleksandr Oparin
Aleksandr Oparin
Alexander Ivanovich Oparin was a Soviet biochemist notable for his contributions to the theory of the origin of life, and for his authorship of the book The Origin of Life. He also studied the biochemistry of material processing by plants, and enzyme reactions in plant cells...

 have demonstrated that they may be formed spontaneously, in conditions similar to the environment thought to exist on an early Earth. These experiments formed liposome
Liposome
Liposomes are artificially prepared vesicles made of lipid bilayer. Liposomes can be filled with drugs, and used to deliver drugs for cancer and other diseases. Liposomes are composite structures made of phospholipids and may contain small amounts of other molecules...

s and microspheres, which have membrane structure
Membrane structure
Membrane structures are one sort of spatial structures made of tensioned membranes.The common membranes include fabrics such as PVC coated polyester fabric, translucent Polyethylene Fabrics, PVC coated glass fiber fabric and PTFE coated glass fiber fabric; foils like ETFE foil and PVC foil...

 similar to the phospholipid bilayer found in cell
Cell (biology)
The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos....

s.

Nanobe
Nanobe
A nanobe is a tiny filamental structure first found in some rocks and sediments. Some scientists hypothesize that nanobes are the smallest form of life, 1/10 the size of the smallest known bacteria...

s or nanobacteria, being too small to be functional living organisms, may be an example of naturally occurring protobionts.
The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
x
OK