Amino acids structures| 9 essential amino acids formula

Incase Isoleucine, Leucine,Tryptophan,Lysine, Methionine, Histidine, Phenylalanine, Threonine, and Valine all are essential amino acids.

What is Amino Acid?

Amino acid means which molecules are present in an amine group and correspondingly acetic group like COOH. All amino acids are different types of the amine group and acetic groups are present in cases 1 Degree amine (Primary Amine), 2-degree amine (Secondary Amine), 3-degree amine (Tertiary Amine).

Amino acid formula

That means amino acids are organic compound content amino(-NH2) and carboxyl(-COOH) groups along with side chains specific for each amino acid which is denoted by X.

amino acid structures/ structure of an amino acid

Can be classified according to the core structure of amino acid- Alpha-amino acid, Beta acid amino acid, Gamma amino acid, and Delta amino acid.

Structure of an amino acid

NH2CH(X)COOH  This is the alpha-amino acid,  NH2CH(X)CH2COOH This is the beta-amino acid, NH2CH(X)CH2CH2COOH This is the Gamma amino acid.

In the formation of protein amino acids play a good role. Many amino acids with Bond and formation of protein. The human nucleus and tissue corresponding to protein beyond the rule reside in protein amino acids that participate in the number of processes that are the transport and biosynthesis.

Structural Features of amino acid

  • The human body or natural source has 20 amino acids present. All 20 amino acids have a common structure only changes their x group which is attached with alpha carbon. All human body amino acids are Alpha-amino acids. They have different types of groups like the aromatic group they have attached with the Amino acid group. 
  • All amino acids have an amino group( -NH2) and carboxylic group(-COOH) And a hydrogen-bonded to the same carbon atom. 
  • In the below, amino acid x group is the side chain of the amino acid which is attached with Alpha carbon.
  • X group Vary structure, size, and electronic charge of the amino acid. X group In the influence of the solubility of amino acid in water.

Stereo configuration of Alpha-amino acid

All-natural amino acids except glycine are asymmetric carbon. In case the x group is the same but they are still your configuration will be changed for the amino acid. D-acid amino acid And L-amino acid for the Amino group is on the right and the amino group is on the left Respectively. 

Read More: Zwitterion and isoelectric point: Definition, separation of amino acid, TLC

A total of 20 amino acids are classified into 7 standard lines by amino acid structure. 
  1. Aliphatic amino acid
  2. Aromatic amino acid
  3. Amino acid with OH group
  4. Amino acid with Sulphur group
  5. Acidic amino acid
  6. Basic amino acid
  7. Amino acid contain amide group
 Now we'll see that these different types of amino acids have different types of structure; their different types of properties are therefore classified with structural and Stereo configuration.

1. Aliphatic amino acid

  • Naturally, all aliphatic amino acids are Alpha-amino acids. All Alpha-amino acids without Proline are directly attached with Alpha carbon that's why these types of amino acids are called aliphatic amino acids.
  • In case Proline has two-degree Amine(20 Amine) that's why these types of Alpha-amino acid are called Alpha imino acid.
  • All amino acids are chiral except the glycine amino acid.
All aliphatic amino acids are glycine(Gly), alanine(Aly) valine(Val), leucine(Leu), isoleucine(Lie) Proline(Pro).

In case glycine Alpha carbon is attached with a single hydrogen atom. Therefore glycine has two same groups of hydrogen are present so glycine is an achiral aliphatic amino acid.

Aliphatic amino acid

Similarly, alanine is attached with -CH3 group, Valine is attached with -CH(CH3)2 Group, Leucine is attached with -CH2CH(CH3)2 group, Isoleucine is attached with -CH(CH3)CH2CH3 Group.

2. Aromatic amino acid

Aromatic groups attached with amino acids These types of amino acids are known as aromatic amino acids. Naturally, three aromatic amino acids are phenylalanine(Phe), tyrosine(Tyr), tryptophan(Trp).
  • In case phenyl aromatic amino acids attach with the benzyl group.
  • Similarly, tyrosine aromatic amino acids are attached with the para hydroxy benzyl group.
  • And tryptophan aromatic amino acid is attached with an indole ring.
  • All groups are aromatic therefore these types of amino acids are called aromatic amino acids.

All aromatic amino acids participate in a protein chain formation. What should be the structure of protein like attached with amino acid they have briefly discussed on another slide.

3. Amino acid attached with Hydroxyl group(-OH)

Now amino acids are attached to the OH group. There are two Amino acids, one is Serine(Ser), and another is Threonine(Thr). 
  • Serine Alpha carbon is attached to the -CH2OH group.
  • And similarly, Threonine attaches with -CH(OH)CH3 group.

4. Amino acid attached with Sulphur group

Amino acids are directly attached with the Sulphur group; their examples are Cysteine(Cys), Methionine(Met), Cystine.
  • All amino acids are S- configuration generally Except Cysteine.
  • In case Cysteine is R configuration.
  • Two cysteine amino acids are dehydrated then the product will be formed with Cystine.
  • Cysteine  + Cysteine ➡ Cystine +H2
  • And methionine is attached to the CH2CH2S(CH3) group.


5. Acidic amino acid

Amino acids attach with an acidic group that is known as acidic amino acids. Examples of acidic amino acids are aspartic acid(Asp),  glutamic acid(Glu). 
  • In case aspartic amino acids are directly attached with the -CH2COOH group. Therefore they have extra acetic groups so that means Normally amino acids increase the acidity of this molecule. 
  • Similarly, glutamic acid is attached to the CH2CH2COOH group.


Acidic amino acid

You can question which one amino acid is the more acidic option, one is the aspartic acid option and two are glutamic acid. 

Clearly, we see that compare two distances between the amino group and acetic group. Now in cases, the aspartic acid distance between the amino group and the acetic group is less compared to glutamic acid. Therefore in cases, aspartic acid has a greater -I effect compared to glutamic acid. That's why aspartic acid releases more H+ ions compared to glutamic acid.

On the other hand, glutamic acid has a greater distance between the amino group and the acetic group. Therefore they have the -I effect less, corresponding to their releasing power of H+ ion is less. So glutamic acid has less acid compared to aspartic acid.
Aspartic acid is more acidic compared to all-natural amino acids.

6. Basic amino acid

The amino acids are attached with basic groups like NH2
  • Examples of basic amino acids are Lysine(Lys), Arginine(Arg), Histidine(His).
  •  In case Lysine contains CH2(CH2)3NH2 group.
  • Similarly, Arginine is attached to the Guanidine unit, -CH2(CH2)2NHC(NH)NH2 Group. In case NHC(NH)NH2 is the Guanidine unit.
  • In histidine amino acids have an imidazole ring.
  • Arginine is a more basic amino acid compared to all-natural amino acids.

Arginine is a more basic amino acid compared to all amino acids due to the presence of Guanidine unit which increases the basicity of the compound.

Guanidine has a more conjugative structure compared to other basic amino acids like Lysine, Histidine. That's why they increase the basicity of Arginine.

Now last step- Amino acid Structure

7. Amino acid content Amide group

Amino acid Alpha carbon is directly attached with the amide group(-CONH2). Examples of amino acids containing amide groups attach Asparagine(Asn),  glutamine(Gm).
  • In Asparagine(Asn) Content amide groups like this -CH2CONH2, group.
  • Glutamine contains an amide group like this -CH2CH2CONH2 Group.

Hydrolysis of the amide group

We know that Hydrolysis of amide groups in presence of basic (OH-) with products from acidic products. That's why we have to see hydrolysis of Asparagine compounds and get the product aspartic acid. 
  • Asparagine +Hydrolysis ➡  Aspartic acid
We have to see the hydrolysis of glutamine compounds and products from Glutamic acid.
  • Gln + Hydrolysis ➡ Glu

Frequently asked question

Q1. What are essential amino acids?

 Ans: The essential amino acid that means Not only generate on your body amino acid-rich source on natural foot. Like daily routine food, amino acids. Amino acids are bound together and the formation of protein is very essential for human body parts. Total 20 amino acids 9 essential amino acids are present in nature. In case Isoleucine, Leucine, Tryptophan, Lysine, Methionine, Histidine, Phenylalanine, Threonine, and Valine all are essential amino acids.

Q2. Is amino acid a protein?

Yes, an amino acid is a protein formation. Many amino acids bind and form protein. All proteins contain amino acids They must be essential or Any work on the body sale or our body tissue. Humans for a very brief part of the protein. That means we call that amino acids are good for the human body. We can see that these types of proteins are work full for the human body. 


We are trying to understand what amino acid is and what is the classification of amino acids. Finally, we have the Amino acid sequence for different types of attachments with groups. You can see that they have 20 amino acids that are formed of protein. We see what is the amino acid and what is the amino acid definition.