Whyis peptide bond formationthermodynamically unfavorable The question of whether peptide bond formation is spontaneous is a nuanced one, as it depends heavily on the cellular or environmental context. While the direct reaction between an amino group and a carboxyl group to form a peptide bond (a type of amide bond) is thermodynamically unfavorable under standard conditions, biological systems have evolved sophisticated mechanisms to drive this essential process. In essence, the formation of peptide bonds is not spontaneous in the simple chemical sense but is coupled with energy-releasing reactions within the cell.
At its core, forming a peptide bond involves the condensation of two amino acids, releasing a molecule of water. This reaction, if considered in isolation, has a positive Gibbs free energy change, meaning it requires an input of energy to proceed. This is why chemical synthesis of peptides often requires activating the carboxyl group of one amino acid, for example, by converting it into a more reactive ester or acid anhydride.
However, within living organisms, this energy input is provided by the hydrolysis of high-energy molecules, most notably ATP (adenosine triphosphate). The cellular machinery, primarily ribosomes, utilizes the energy released from ATP hydrolysis to activate amino acids and facilitate their precise assembly into polypeptide chains. This process, while seemingly complex, is a prime example of how biological systems achieve non-spontaneous reactions by coupling them with spontaneous, energy-releasing ones.
It's crucial to distinguish between peptide bond formation and peptide bond hydrolysis. Hydrolysis, the breaking of a peptide bond by the addition of water, is generally spontaneous and exergonic2026. This is the reverse of peptide bond formationforspontaneousand non-spontaneousprocess, criteria for equilibrium. ... Proteins – Elementary idea of – amino acids,peptide bond, polypeptides, proteins, .... While the hydrolysis of peptide bonds is thermodynamically favorable, it often proceeds very slowly in vivo due to a high activation energy barrier. Enzymes called proteases are responsible for catalyzing this bond breakage, allowing for protein turnover and regulation.It is determined by the order of amino acids linked bypeptide bonds. Carbohydrate Chemistry: Key concepts in carbohydrate chemistry include ... The spontaneous flow of solvent through a semipermeable membrane, mentioned in some contexts, relates to osmotic pressure and is a different thermodynamic phenomenon, not directly tied to peptide bond kineticsPeptide bondscan be broken down rapidly through hydrolysis using chemical catalysts, such as acids or enzymes known as proteases. Breaking ofpeptide bonds....
While the formation of peptide bonds within the main chain of proteins is typically an energetically driven process, there are instances where spontaneously forming intramolecular isopeptide bonds can occur. These bonds form outside the main polypeptide backbone and have been observed in specific conditions, sometimes facilitated by environmental factors.Peptide bond - Wikipedia For example, research has shown that peptide bond formation can occur spontaneously at the water–air interface, particularly when facilitated by the formation of a copper complex. These findings suggest that under certain specific, often non-physiological, conditions, the formation of peptide bonds might exhibit a degree of spontaneity, albeit often requiring specific catalysts or interfaces.
In summary, the direct chemical reaction leading to peptide bond formation is not spontaneous in a biological context without an energy input. This energy is supplied by cellular processes, primarily involving ATP.作者：V Siegmund·2016·被引用次数：61—Spontaneously forming intramolecular isopeptide bonds—peptide bonds that form outside of the protein main chain—were first discovered a decade ... While spontaneous formation of isopeptide bonds can occur under specific environmental conditions, the primary mechanism for creating the polypeptide chains that form proteins relies on an actively managed, energy-dependent pathway. Understanding this energetic landscape is fundamental to comprehending protein synthesis and function.
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