What is the Difference Between Amino Acid and Imino Acid

Amino acids and imino acids are both organic compounds important in biochemical processes, but they possess distinct structural and chemical characteristics. Knowing the difference between amino acid and imino acid is fundamental in understanding their diverse roles in biological systems.

What is the difference between amino acid and imino acid? Amino acids have an amino group (NH2), a carboxyl group (COOH), and a side chain (R group) all bonded to a central carbon atom, whereas imino acids have an imine group (NH) in it.

Key Areas Covered

1. What is an Amino Acid 
      – Definition, Features
2. What is an Imino Acid
      – Definition, Features
3. Similarities Between Amino Acid and Imino Acid
      – Outline of Common Features
4. Difference Between Amino Acid and Imino Acid
      – Comparison of Key Differences
5. FAQ: Amino Acid and Imino Acid
      – Answers to Frequently Asked Questions

Key Terms

Amino Acid, Imino Acid

Difference Between Amino Acid and Imino Acid - Comparison Summary

What is an Amino Acid

Amino acids are organic compounds with nitrogen atoms in them. They have both a carboxylic group and an amino group as functional groups, attached to a carbon atom along with hydrophobic side chains. Depending on the environment’s pH, one group might donate a proton, becoming charged, while the other accepts one, becoming neutral. This creates a zwitterion, a molecule with both positive and negative charges, existing at a neutral pH.

These R groups attached to the central carbon atom are of different sizes and shapes. Hence, they affect amino acids’ various properties, such as polarity, solubility, and reactivity. Amino acids are the building blocks of proteins. Amino acids are linked by peptide bonds to form a protein. Peptide bonds are formed between the carboxyl group of one amino acid and the amino group of another.

Amino Acid

Amino acids are essential compounds for life. There are many uses of amino acids. They are sometimes used to produce glucose. Certain amino acids, like tryptophan, are precursors to neurotransmitters, the brain’s chemical messengers. Tryptophan gets converted to serotonin, a neurotransmitter influencing mood, sleep, and appetite. This highlights how amino acids can impact our mental well-being. Some amino acids act as a fuel source for intestinal cells, supporting a healthy gut barrier and immune function.

Other than biological uses, amino acids are extensively used in industries, too. For example, they can be used as biodegradable alternatives to harsh chemicals in cleaning products. Additionally, some amino acids are used in the production of nylon and other synthetic materials.

What is an Imino Acid

Both amino and imino acids have a carboxyl group (like a carboxylic acid) and a group bonded to the same carbon atom. In amino acids, this group contains a single carbon-nitrogen bond (amino group), while in imino acids, it’s a double bond (imine group). Dehydroglycine, the simplest example, is a derivative of the amino acid glycine. More importantly, some enzymes can convert amino acids into imino acids. 

Imino Acid

Imino acids are less abundant in nature. Their ability to form bonds with other molecules suggests potential uses in medicinal chemistry or material science. Additionally, understanding their role in amino acid synthesis could provide insights into protein production and regulation.

Similarities Between Amino Acid and Imino Acid

  1. Both share a central carbon atom bonded to an amino group (NH2) or an imino group (NH), a carboxyl group (COOH), and a side chain (R group) that determines their unique properties.
  2. They are both organic molecules.

Difference Between Amino Acid and Imino Acid


  • Amino acid is an organic compound containing both an amino group (-NH2) and a carboxyl group (-COOH), which are the building blocks of proteins, while imino acid is an organic compound with a functional group containing a carbon-nitrogen double bond (C=N).


  • Amino acids have an amino group (NH2), while imino acids have an imino group (NH).


  • The bonding of amino acids is more versatile than that of imino acids.


  • Amino acids are more acidic than imino acids.

In Nature

  • Amino acids are abundant in nature, whereas imino acids are less commonly found in nature.


In conclusion, amino acids and imino acids share structural similarities, both containing a central carbon atom, a carboxyl group, and a unique side chain. However, the main difference between amino acid and imino acid lies in the nature of the group bonded to this central carbon; amino acids feature an amino group (NH2), while imino acids contain an imino group (NH).

FAQ: Amino Acid and Imino Acid

1. What is the imino group?

An imino group (C=N) is a nitrogen-containing active functional group formed after the oxygen atom on the carbonyl is replaced by a nitrogen atom.

2. What are the 4 types of amino acids?

The four types of amino acids based on the location of functional groups are, alpha amino acids, beta amino acids, gamma amino acids, and delta amino acids.

3. What is an example of an imino acid?

An example of an imino acid is hydroxyproline, which plays a significant role in the structure and stability of collagen protein in connective tissues.

4. Is glycine an imino acid?

No, glycine is not an imino acid. Glycine is the simplest amino acid and does not contain an imino group (C=N). Instead, it has a single hydrogen atom as its side chain.

5. What is an amino group?

 An amino group consists of one nitrogen atom and two hydrogen atoms bonded through covalent bonds. Amino groups consist of nitrogen-to-hydrogen single bonds.


1. “Amino Acid.” Encyclopedia Britannica.
2. “Imino Acid – An Overview.” Science Direct.

Image Courtesy:

1. “L-amino acid structure” By Smokefoot – Own work (Public Domain) via Commons Wikimedia
2. “L-proline-skeletal” By Ben Mills – Own work (Public Domain) via Commons Wikimedia


About the Author: Hasini A

Hasini is a graduate of Applied Science with a strong background in forestry, environmental science, chemistry, and management science. She is an amateur photographer with a keen interest in exploring the wonders of nature and science.

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