What is dehydration synthesis?

Dehydration synthesis, also known as condensation reaction, is a type of chemical reaction where two molecules are joined together by the removal of a water molecule. Here's a breakdown of the process:

Mechanism:

• Hydroxyl group (-OH) and hydrogen atom (-H): One molecule contributes a hydroxyl group (-OH), and the other contributes a hydrogen atom (-H). These come from functional groups on the reacting molecules.
• Water molecule formation: These two groups combine to form a molecule of water (H₂O).
• Covalent bond formation: The remaining portions of the two molecules then become covalently bonded together.

Examples:

• Formation of disaccharides: Two monosaccharides (simple sugars like glucose and fructose) can undergo dehydration synthesis to form a disaccharide (like sucrose). A water molecule is removed, and a glycosidic linkage is formed between the two monosaccharides.
• Formation of polypeptides: Amino acids are linked together through peptide bonds during protein synthesis. This involves a dehydration reaction where a water molecule is removed between the carboxyl group (-COOH) of one amino acid and the amino group (-NH₂) of another.
• Formation of phosphodiester bonds in DNA and RNA: Nucleotides are joined together through phosphodiester bonds to form the nucleic acid chains. This process also involves the removal of a water molecule.
• Synthesis of fats and oils (triglycerides): Glycerol and fatty acids combine through dehydration synthesis to form triglycerides (fats or oils), with a water molecule removed for each ester bond formed.

Significance:

Dehydration synthesis is crucial for building large, complex molecules (polymers) from smaller subunits (monomers) in living organisms. It's a fundamental process in anabolism, the constructive phase of metabolism.

Opposite reaction:

The reverse reaction of dehydration synthesis is hydrolysis, where a water molecule is added to break a covalent bond between two molecules.