How did ribosomes work without proteins?
Submitted By
JasonGrade Level
11Answered by
Adam OrrHi, Jason.
This is a great question that has sparked a lot of interest:
If a ribosome is required to make proteins, but the ribosome itself is made of proteins, how did proteins first form?
While this seems puzzling, the mystery started to unravel when scientists began to look at how ribosomes work.
Ribosomes use RNA to make protein
They focused on the part of the ribosome that helps amino acids to join (making proteins). This part of the ribosome is made of RNA. The other parts of the ribosome, that are made of protein, only play a structural role and help keep the molecule stable.
Enzymes are molecules that help make chemical reactions happen. While many enzymes are proteins, there are also many enzymes made of only RNA; these are called ribozymes. Because the ribosome is a ribozyme, that means that an RNA-only molecule could help with protein formation.
The RNA World Hypothesis
Thus, it's very likely that the first ribosomes were only made of RNA. The protein parts of the molecule were likely added later, and helped prevent it from breaking down. This is part of a wider body of work focused on the very beginning of life on Earth—the RNA World Hypothesis.
The hypothesis considers the observations that:
- RNA can be used to store information in its sequence
- RNA can perform functional roles and catalyze (help or speed up) reactions
It suggests that the first life forms used RNA for both these functions.
DNA and proteins evolved later and are more stable. But there was likely a time when all organisms had RNA genomes and cellular functions depended on RNA-based enzymes.
No proteins required!
Additional images via Wikimedia Commons.
Bibliographic details:
- Article: How did ribosomes work without proteins?
- Author(s): Dr. Biology
- Publisher: Arizona State University School of Life Sciences Ask A Biologist
- Site name: ASU - Ask A Biologist
- Date published: 16 Jul, 2019
- Date accessed:
- Link: https://askabiologist.asu.edu/questions/ribosomes-and-proteins
APA Style
Dr. Biology. (Tue, 07/16/2019 - 11:02). How did ribosomes work without proteins?. ASU - Ask A Biologist. Retrieved from https://askabiologist.asu.edu/questions/ribosomes-and-proteins
Chicago Manual of Style
Dr. Biology. "How did ribosomes work without proteins?". ASU - Ask A Biologist. 16 Jul 2019. https://askabiologist.asu.edu/questions/ribosomes-and-proteins
MLA 2017 Style
Dr. Biology. "How did ribosomes work without proteins?". ASU - Ask A Biologist. 16 Jul 2019. ASU - Ask A Biologist, Web. https://askabiologist.asu.edu/questions/ribosomes-and-proteins
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