What is the Difference Between Left and Right Handed Amino Acids?
🆚 Go to Comparative Table 🆚The difference between left and right-handed amino acids lies in their chirality, which refers to the "handedness" of the molecule. While most amino acids can exist in both left and right-handed forms, life on Earth is made of left-handed amino acids almost exclusively. The only exception is some bacteria that can convert right-handed amino acids into the left-handed version but cannot use the right-handed ones as is.
The key difference between left and right-handed amino acids is the position of the amine group in the molecule:
- Left-handed amino acids: The amine group is on the left-hand side, and the carboxylic group is on the right-hand side.
- Right-handed amino acids: The amine group is on the right-hand side, and the carboxylic group is on the left-hand side.
There are two main theories about why life on Earth uses only left-handed amino acids:
- Extraterrestrial origin: Some amino acids that fall to Earth from space favor the L form, and this may be the reason why life on Earth is made of L amino acids. However, this theory is still speculative.
- Bonner hypothesis: This theory proposes that left-handed radiation in space could have caused the left-handed amino acids found in meteorites. This hypothesis is also still under investigation.
In summary, the primary difference between left and right-handed amino acids is their chirality, with left-handed amino acids being the building blocks of life on Earth and right-handed amino acids being less utilized by known biological life forms.
Comparative Table: Left vs Right Handed Amino Acids
Left-handed and right-handed amino acids are stereoisomers, which means they have the same molecular formula but different spatial arrangements. The key difference between them is the position of the amine group in relation to the carboxylic group. Here is a table summarizing their differences:
| Left-Handed Amino Acids (L) | Right-Handed Amino Acids (D) |
|---|---|
| Amine group on the left side | Amine group on the right side |
| Also known as L-amino acids | Also known as D-amino acids |
| Mostly used by living organisms for protein synthesis | Less common in nature, found in bacterial cell walls and some antibiotics |
Left-handed amino acids are also called L-amino acids, while right-handed amino acids are called D-amino acids. In Fischer projections, if the NH2 group is on the left side, it's a D-amino acid, and if it's on the right, it's an L-amino acid. Due to their distinct formations, L and D amino acids are not interchangeable. Most life forms use L-amino acids for protein synthesis, while D-amino acids are often found in bacterial cell walls and some antibiotics.
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