Dehydration Synthesis: The Process by Which Two Amino Acids Are Combined Together Called

December 28, 2025 •

2 min read

Did you know that every protein in your body is built by linking amino acids together? The critical process by which two amino acids are combined together is known as dehydration synthesis, a fundamental reaction in biochemistry that enables the creation of complex macromolecules essential for life.

Quick Summary

Amino acids are linked through a dehydration synthesis or condensation reaction, forming a covalent peptide bond. This reaction joins the carboxyl and amino groups of two monomers, releasing a molecule of water to create a dipeptide or polypeptide chain.

Key Points

Dehydration Synthesis: The process of combining two amino acids is called dehydration synthesis or a condensation reaction, which involves the removal of a water molecule.
Peptide Bond: This reaction forms a strong, covalent bond known as a peptide bond, which links the carboxyl group of one amino acid to the amino group of another.
Dipeptide Formation: When two amino acids are joined by one peptide bond, the resulting molecule is specifically called a dipeptide.
Ribosomal Catalysis: In living organisms, the synthesis of peptide bonds is catalyzed by ribosomes during the process of translation.
Hydrolysis: The reverse reaction, which breaks the peptide bond by adding a water molecule, is called hydrolysis and is crucial for digestion.
Polypeptide Chains: Repeated dehydration synthesis reactions build long chains of amino acids called polypeptides, which then fold into functional proteins.

The Fundamental Reaction: Dehydration Synthesis

Proteins are formed by linking amino acid monomers together through a process called dehydration synthesis, also known as a condensation reaction. This reaction builds larger molecules from smaller ones by removing a molecule of water.

The Mechanism of Peptide Bond Formation

During dehydration synthesis, the carboxyl group ($$-COOH$$) of one amino acid reacts with the amino group ($$-NH_2$$) of another. This reaction releases a hydroxyl group ($$-OH$$) from the carboxyl end and a hydrogen atom ($$-H$$) from the amino group, which combine to form a molecule of water ($$H_2O$$). The remaining carbon and nitrogen atoms then form a strong, covalent peptide bond ($$-CO-NH-$$). The molecule resulting from the joining of two amino acids by a peptide bond is called a dipeptide. Repeating this process forms long chains of amino acids called polypeptides, which fold to create functional proteins. This process is crucial in gene expression, converting genetic information into protein sequences.

Directionality and the Peptide Bond

Polypeptide chains have directionality, with an N-terminus having a free amino group and a C-terminus having a free carboxyl group. Amino acid sequences are conventionally read from the N-terminus to the C-terminus. The peptide bond has a rigid, planar structure due to its partial double-bond character, which influences the protein's overall shape.

The Cellular Context of Protein Formation

In living organisms, protein synthesis takes place on ribosomes in the cytoplasm. Ribosomes catalyze peptide bond formation, guided by messenger RNA (mRNA) templates carrying genetic code. Transfer RNA (tRNA) molecules deliver specific amino acids to the ribosome, adding them to the growing polypeptide chain. This energy-requiring process is typically powered by ATP.

The Reverse Reaction: Hydrolysis

The reverse of dehydration synthesis is hydrolysis, which breaks down macromolecules by adding water. Hydrolysis cleaves peptide bonds using a water molecule, restoring the original carboxyl and amino groups. This is vital for digestion, breaking dietary proteins into amino acids for absorption. Protease or peptidase enzymes catalyze hydrolysis in organisms.

Comparison of Dehydration Synthesis and Hydrolysis


Feature	Dehydration Synthesis (Condensation)	Hydrolysis
Process	Anabolic (Builds larger molecules from smaller units)	Catabolic (Breaks larger molecules into smaller units)
Water Involvement	A water molecule is removed	A water molecule is added
Energy	Requires energy input (endergonic)	Releases energy (exergonic)
Bond	Forms a new covalent bond (peptide bond)	Breaks a covalent bond (peptide bond)
Example	Linking amino acids to form a protein	Digesting a protein into amino acids

Conclusion: The Significance of Peptide Bond Formation

The formation of peptide bonds through dehydration synthesis is a fundamental biochemical process enabling the creation of proteins essential for life. The precise control over the formation and breakdown of these bonds is critical for cellular functions like growth and repair. Research into peptide synthesis continues to advance medicine and biotechnology.

Further reading on the fundamental reactions of amino acids can be found in reference materials like the Encyclopaedia Britannica on Amino Acids.

Frequently Asked Questions

A peptide bond is a covalent chemical bond that forms between the carboxyl group ($$-COOH$$) of one amino acid and the amino group ($$-NH_2$$) of another amino acid through dehydration synthesis.

The formation of a peptide bond is an anabolic reaction that requires energy input. In organisms, this energy is derived from the breakdown of ATP (adenosine triphosphate) to drive the reaction forward.

The opposite of dehydration synthesis is hydrolysis. This reaction breaks a peptide bond by adding a water molecule, which is the process used to digest proteins into individual amino acids.

A dipeptide is a molecule that consists of two amino acids joined together by a single peptide bond.

Ribosomes are cellular organelles that act as molecular machines for protein synthesis. They catalyze the formation of peptide bonds between amino acids according to the sequence specified by messenger RNA (mRNA).

A condensation reaction is another name for dehydration synthesis, referring to any reaction where two molecules are combined into a larger molecule with the loss of a smaller molecule, such as water.

The peptide bond is important because it is rigid and planar due to its partial double-bond character, which constrains the shape of the polypeptide backbone and is crucial for a protein's overall three-dimensional structure and function.