Main Difference – Amino Acid vs Protein
Amino acid and protein are two types of important biomolecules in the animal body. An amino acid sequence that is bound together as a string via peptide bonds is called a protein. The main difference between amino acid and protein is that amino acid is the building block of a protein whereas protein plays a vital role in the body as a structural and functional molecule. Twenty amino acids are involved in the synthesis of proteins inside living organisms. Both Amino acids and proteins can be taken into the body through the diet. Proteins in the diet are broken down into amino acids during digestion. Therefore, our body synthesizes all proteins required by the functioning of a body cell. The amino acid sequence of a protein is determined by the instructions in genes.
Key Areas Covered
1. What is an Amino Acid
– Definition, Structure, Role in the Body
2. What is a Protein
– Definition, Structure, Role in the body
3. What are the Similarities Between Amino Acid and Protein
– Outline of Common Features
4. What is the Difference Between Amino Acid and Protein
– Comparison of Common Features
Key Terms: Amino Acid, Codon, Complete Protein, Essential Amino Acids, Gene, Genetic Code, Incomplete Protein, Protein
What is an Amino Acid
An amino acid refers to a simple organic molecule in the body. Generally, twenty different amino acids, which serve as building blocks of proteins, can be identified. They are called universal amino acids. All amino acids share a common, basic structure in which four chemical groups bind to the central carbon atom. These four chemical groups are an amino group (NH2), a carboxylic acid group (COOH), a hydrogen atom (H), and a variable side chain (R). Both carboxylic and amino groups are attached to the same carbon. The structure of a typical amino acid is shown in figure 1.
Figure 1: Structure of an Amino Acid
Based on the composition of the R group, the physical and chemical properties of the universal amino acid may differ from each other. Each of the universal amino acids is represented by a codon in the genetic code. The codon sequence of a particular protein is determined by the nucleotide sequence of a gene. Genes are transcribed into mRNA and those mRNAs are decoded with the help of ribosomes to produce a primary protein. The structure and properties of universal amino acids are shown in figure 2.
Figure 2: Universal Amino Acids
Other than the twenty universal amino acids, further two amino acids can be identified as modified variants only in certain organisms. They are selenocysteine and pyrrolysine. In humans, nine amino acids are considered as essential amino acids since they cannot be synthesized by the body. Therefore, these amino acids should be included in the diet. These nine, essential amino acids are alanine, asparagine, aspartic acid, cysteine, glutamic acid, glutamine, glycine, proline, and serine.
Other amino acids are synthesized inside the body in various biochemical pathways.
What is a Protein
A protein is a large, nitrogenous, organic compound, composed of one or two amino acid chains. A protein is made up of an alternative assembly of universal amino acids. Hence, a protein is a polymer. Peptide bonds are formed between amino groups and carboxyl acid groups of adjacent amino acids. Thus, proteins are also called polypeptides. Typically, a natural polypeptide may consist of 50 – 2000 amino acids. However, proteins are very complex and dynamic type of molecules, consisting of four structural levels: primary, secondary, tertiary, and quaternary structure. Different combinations of amino acids give different properties to proteins. Humans have of 20,000 to 25,000 protein-coding genes. From that, about 2 million of different protein types can be synthesized. However, the human body consists of around 50,000 proteins. The study of the structure and function of those proteins is called proteomics. The main structural levels of a protein are shown in figure 3.
Figure 3: Structural Levels of a Protein
Proteins are included in the food either as complete proteins or incomplete proteins. A complete protein may consist of all the essential amino acids while an incomplete protein may lack some of them. These proteins are broken down into amino acids during digestion. Therefore, each cell in the body can gather amino acids from the bloodstream to synthesize different types of proteins they need. Proteins serve as a structural component of a cell. They also regulate the functions of the body as hormones and enzymes. They also serve as transporting molecules. For example, hemoglobin is the protein that transports oxygen throughout the body. Proteins produce molecules of the immune system as well.
Similarities Between Amino Acid and Protein
- Amino acids and proteins are two important biomolecules in animals.
- Both amino acids and proteins are made up of C, H, O, N, and S.
- Both amino acids and proteins can be taken into the body through the diet.
- Both amino acids and proteins can be synthesized inside the body.
- The amino acid sequence of a protein is determined based on the information in genes.
Difference Between Amino Acid and Protein
Definition
Amino Acid: An amino acid refers to a simple organic molecule, containing both carboxyl and amino group.
Protein: A protein refers to a large, nitrogenous, organic compound, composed of one or two amino acid chains.
Correlation
Amino Acid: Amino acids are the building blocks of proteins.
Protein: A protein is a string of amino acids.
Synthesis Inside the Body
Amino Acid: Only some of the amino acids can be synthesized inside the body.
Protein: All the proteins required by the body are synthesized inside the body.
Molecular Mass
Amino Acid: Amino acids have a small molecular mass.
Protein: Proteins are macromolecules. Therefore, they have a higher molecular mass.
Number
Amino Acid: Twenty amino acids are involved in the synthesis of proteins in all living organisms.
Protein: More than 10 million of proteins are produced in biological organisms.
Structure
Amino Acid: An amino acid is composed of an amino group (NH2), a carboxylic acid group (COOH), a hydrogen atom (H), and a variable side chain (R).
Protein: Proteins are made up of amino acids linked together by peptide bonds.
Function
Amino Acid: Amino acids are involved in the protein synthesis.
Protein: Proteins serve as a structural, functional, and regulatory molecule in the body.
How are Proteins Constructed from Amino Acids
Conclusion
Amino acid and protein are two important amino acids in the body. Amino acids are the building blocks of proteins. Proteins are the most abundant biomolecules in the body, serving as a structural, functional, and regulatory molecule. The main difference between amino acid and protein is the function of each molecule in the body.
Reference:
1. “Amino Acids”, BioNinja, Available here.
2.“How many Proteins exist in human body?” Innovateus.net, Available here.
Image Courtesy:
1. “AminoAcidball” By GYassineMrabetTalk✉This vector image was created with Inkscape. – Own work, Public Domain) via Commons Wikimedia
2. “Amino Acids” By Dancojocari – Own work This vector graphics image was created with Adobe Illustrator.iThe source code of this SVG is valid. (CC BY-SA 3.0) via Commons Wikimedia
3. “Main protein structure levels en” By LadyofHats – Own work (ublic Domain) via Commons Wikimedia
Leave a Reply