How are amino acids linked to form polypeptides?

Amino acids are linked to form polypeptides through a process called dehydration synthesis, forming peptide bonds.

In more detail, the process of linking amino acids to form polypeptides is a fundamental part of protein synthesis. This process is facilitated by a reaction known as dehydration synthesis, also referred to as a condensation reaction. This is because it involves the removal of a water molecule (H2O) during the formation of the bond.

Each amino acid has a central carbon atom, which is bonded to an amino group (-NH2), a carboxyl group (-COOH), a hydrogen atom, and a unique side chain (R group). The peptide bond is formed between the carboxyl group of one amino acid and the amino group of the next. During this process, the carboxyl group loses a hydroxyl group (-OH) and the amino group loses a hydrogen atom, which together form a water molecule. This is why the process is called dehydration synthesis, as a water molecule is effectively 'removed'.

The resulting bond between the two amino acids is a peptide bond, creating a dipeptide. This process can be repeated with additional amino acids to form a polypeptide chain. The sequence of amino acids in this chain is determined by the sequence of nucleotides in the DNA, which is transcribed into mRNA during the process of transcription. The mRNA is then translated into a polypeptide chain during the process of translation.

The formation of peptide bonds is a crucial process in biology, as it allows for the creation of proteins, which are essential for many biological functions. Proteins can act as enzymes, structural components of cells, transport molecules, antibodies, and more. Therefore, understanding the process of peptide bond formation and protein synthesis is fundamental to understanding how cells function.

Remember, the process of forming a peptide bond is an endothermic reaction, meaning it requires energy. This energy is provided by ATP (adenosine triphosphate), the main energy currency of the cell. The reaction is catalysed by enzymes known as ribosomes, which are the protein factories of the cell.