Amino acids : Definition , Structure and Function
Definition
Amino acids are organic molecules that serve as the building blocks of proteins. They are composed of an amino group (-NH2), a carboxyl group (-COOH), a hydrogen atom, and a side chain (R group) that is unique to each amino acid. There are 20 different types of amino acids that can be found in nature, each with a different side chain. Amino acids are linked together through peptide bonds to form proteins. In addition to their role in protein synthesis, some amino acids also serve as neurotransmitters, precursors to other molecules, and energy sources for the body.
Composition of amino acid
As mentioned earlier, amino acids are composed of an amino group (-NH2), a carboxyl group (-COOH), a hydrogen atom, and a side chain (R group) that is unique to each amino acid. The amino group consists of a nitrogen atom bonded to two hydrogen atoms, while the carboxyl group consists of a carbon atom double-bonded to an oxygen atom, and also single-bonded to a hydroxyl group (-OH). The side chain, or R group, can be anything from a simple hydrogen atom to a complex ring structure, and it determines the chemical properties and behavior of each amino acid.
The general chemical formula for an amino acid is:
H2N-CHR-COOH
Where H2N represents the amino group, CHR represents the variable side chain, and COOH represents the carboxyl group.
List of 20 Amino acids with chemical formula
Here is a list of the 20 amino acids, their abbreviations, and chemical formulas:
- Alanine (Ala, A) - C3H7NO2
- Arginine (Arg, R) - C6H14N4O2
- Asparagine (Asn, N) - C4H8N2O3
- Aspartic acid (Asp, D) - C4H7NO4
- Cysteine (Cys, C) - C3H7NO2S
- Glutamine (Gln, Q) - C5H10N2O3
- Glutamic acid (Glu, E) - C5H9NO4
- Glycine (Gly, G) - C2H5NO2
- Histidine (His, H) - C6H9N3O2
- Isoleucine (Ile, I) - C6H13NO2
- Leucine (Leu, L) - C6H13NO2
- Lysine (Lys, K) - C6H14N2O2
- Methionine (Met, M) - C5H11NO2S
- Phenylalanine (Phe, F) - C9H11NO2
- Proline (Pro, P) - C5H9NO2
- Serine (Ser, S) - C3H7NO3
- Threonine (Thr, T) - C4H9NO3
- Tryptophan (Trp, W) - C11H12N2O2
- Tyrosine (Tyr, Y) - C9H11NO3
- Valine (Val, V) - C5H11NO2
Note that the chemical formulas listed above are for the amino acids in their neutral, uncharged form at physiological pH. The side chains or R groups of each amino acid have a different chemical structure and formula, which contribute to their unique properties and functions.
Structure of amino acids
The structure of an amino acid can be described in different ways depending on the level of detail required.
At the simplest level, the structure of an amino acid can be represented as a single letter abbreviation, where each letter corresponds to a specific amino acid. For example, glycine is represented by the letter "G", and arginine is represented by the letter "R".
At a slightly more detailed level, the structure of an amino acid can be represented as a three-letter abbreviation, where the first letter represents the side chain and the other two letters represent the amino acid backbone. For example, glycine is represented as "Gly", and arginine is represented as "Arg".
At the most detailed level, the structure of an amino acid can be represented using a chemical diagram that shows the specific arrangement of atoms within the molecule. As mentioned earlier, amino acids consist of an amino group (-NH2), a carboxyl group (-COOH), a hydrogen atom, and a side chain (R group) that is unique to each amino acid. These components are arranged around a central carbon atom called the alpha carbon (α-carbon), which is bonded to the amino group, the carboxyl group, the hydrogen atom, and the side chain. The arrangement of these components around the alpha carbon gives each amino acid its distinct chemical and physical properties.
Types of amino acids
There are 20 different types of amino acids that are found in proteins, each with a unique side chain or R group. These amino acids can be classified into different categories based on their chemical properties. Here are the categories of amino acids:
Non-polar (hydrophobic) amino acids: These amino acids have a side chain that is made up of only carbon and hydrogen atoms, which makes them insoluble in water. Examples include alanine, valine, leucine, isoleucine, methionine, phenylalanine, and tryptophan.
Polar (hydrophilic) amino acids: These amino acids have a side chain that contains functional groups that can form hydrogen bonds with water molecules, which makes them soluble in water. Examples include serine, threonine, cysteine, asparagine, glutamine, and tyrosine.
Charged amino acids: These amino acids have a side chain that contains a positive or negative charge, which makes them highly soluble in water. Examples include lysine, arginine, histidine, aspartic acid, and glutamic acid.
Special amino acids: These are amino acids that have unique properties that do not fit into the other categories. Examples include proline, which has a cyclic structure that restricts its mobility and flexibility, and glycine, which is the smallest amino acid and has a hydrogen atom as its side chain.
Understanding the different types of amino acids is important in understanding how they contribute to protein structure and function. The unique properties of each amino acid determine how it interacts with other amino acids and with its environment, which in turn affects the overall structure and function of the protein.
Application of amino acids
Amino acids have a wide range of applications in various fields. Some of the applications of amino acids are:
Protein synthesis: Amino acids are the building blocks of proteins, and they are used to synthesize new proteins in the body.
Dietary supplements: Amino acid supplements are used by athletes and bodybuilders to enhance muscle growth and recovery.
Medical applications: Amino acids are used in medical treatments for conditions such as phenylketonuria (PKU), a genetic disorder that affects the metabolism of amino acids, and chronic fatigue syndrome.
Food and beverage industry: Amino acids are used as food additives to enhance flavor, improve texture, and extend shelf life.
Agriculture: Amino acids are used as fertilizers to improve soil quality and increase crop yields.
Cosmetic industry: Amino acids are used in cosmetics and personal care products to improve skin and hair health.
Industrial applications: Amino acids are used in various industrial processes, such as the production of biodegradable plastics and other materials.
Biotechnology: Amino acids are used in biotechnology research and development, including the production of biofuels and biopharmaceuticals.
Essential and Non essential amino acids
Essential amino acids are amino acids that cannot be synthesized by the human body and must be obtained from the diet. There are nine essential amino acids: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine.
Non-essential amino acids, on the other hand, are amino acids that can be synthesized by the human body from other amino acids and molecules. There are 11 non-essential amino acids: alanine, arginine, asparagine, aspartic acid, cysteine, glutamic acid, glutamine, glycine, proline, serine, and tyrosine.
It is important to consume a balanced diet that includes sources of all essential amino acids in order to support protein synthesis and maintain overall health. Many sources of animal protein, such as meat, fish, and dairy products, contain all essential amino acids in sufficient quantities. Plant-based sources of protein, such as legumes, nuts, and seeds, may lack one or more essential amino acids, but consuming a variety of these foods can provide all the necessary amino acids.
Diffreence between essential and non essential amino acids
The main difference between essential and non-essential amino acids is that essential amino acids cannot be produced by the body and must be obtained from the diet, while non-essential amino acids can be synthesized by the body from other amino acids and molecules.
Essential amino acids are essential for the synthesis of proteins and other important molecules in the body. They are important for growth, repair, and maintenance of tissues, and they play a role in many metabolic processes. If the diet lacks any essential amino acids, protein synthesis and metabolic processes may be impaired, which can lead to various health problems.
Non-essential amino acids, on the other hand, are still important for protein synthesis and other metabolic processes in the body, but they can be synthesized from other amino acids or from other molecules in the body. Therefore, they are not required in the diet to the same extent as essential amino acids.
In summary, essential amino acids are those that must be obtained from the diet, while non-essential amino acids can be synthesized by the body. Both types of amino acids are important for the synthesis of proteins and other molecules, but the body has different requirements for essential and non-essential amino acids.
Most Important Question
What are amino acids?
Amino acids are organic compounds that serve as the building blocks of proteins. They contain an amino group (-NH2), a carboxyl group (-COOH), and a side chain (R group), which gives each amino acid its unique properties.
How many types of amino acids are there?
There are 20 types of amino acids that are commonly found in proteins. These amino acids differ from one another in their side chains or R groups, which can be polar, nonpolar, acidic, or basic.
What is the difference between essential and non-essential amino acids?
Essential amino acids are amino acids that cannot be synthesized by the human body and must be obtained from the diet. There are nine essential amino acids. Non-essential amino acids, on the other hand, can be synthesized by the body from other amino acids and molecules.
What is the role of amino acids in the body?
Amino acids are the building blocks of proteins, which are important for the growth, repair, and maintenance of tissues in the body. Amino acids also play a role in many metabolic processes, such as the synthesis of hormones, neurotransmitters, and enzymes.
What are some food sources of amino acids?
Many sources of animal protein, such as meat, fish, and dairy products, contain all essential amino acids in sufficient quantities. Plant-based sources of protein, such as legumes, nuts, and seeds, may lack one or more essential amino acids, but consuming a variety of these foods can provide all the necessary amino acids.
Can amino acids be harmful to the body?
In general, amino acids are not harmful to the body when consumed in moderation as part of a balanced diet. However, excessive intake of certain amino acids or supplements can lead to negative health effects, such as kidney damage, gastrointestinal problems, or interference with the absorption of other nutrients.
What is the difference between L-amino acids and D-amino acids?
L-amino acids and D-amino acids are mirror images of each other and differ in their spatial arrangement. L-amino acids are the primary amino acids found in proteins, while D-amino acids are less common and are typically found in non-protein molecules.
What are some common uses of amino acids in industry?
Amino acids have a wide range of industrial applications, such as in the production of food additives, pharmaceuticals, and cosmetics. They are also used as a nutrient supplement in animal feed and as a substrate for the production of biodegradable plastics and other materials.
Can amino acids be used for weight loss?
Amino acid supplements are sometimes marketed as weight loss aids, but there is limited scientific evidence to support their effectiveness. A balanced diet that includes sources of all essential amino acids is important for supporting weight loss and maintaining overall health.
What is the difference between a peptide bond and a covalent bond?
A peptide bond is a type of covalent bond that forms between the amino group of one amino acid and the carboxyl group of another amino acid during protein synthesis. Peptide bonds are responsible for linking amino acids together to form proteins.