Question

Would you expect the biosynthesis of a protein from the constituent amino acids in an organism to be an exergonic or endergonic process? Give the reason for your answer

Short answer

Protein biosynthesis is endergonic because it requires energy.

Step-by-step solution

Understand Exergonic and Endergonic Processes

Exergonic processes release energy, typically in the form of heat, and occur spontaneously. Endergonic processes require an input of energy to proceed and are not spontaneous.

Define Protein Biosynthesis

Protein biosynthesis is the process by which cells build proteins from amino acids, involving various biochemical reactions including transcription and translation.

Energy Requirements of Protein Biosynthesis

Consider that to assemble a protein, the cell requires energy to form peptide bonds between amino acids. This energy typically comes from ATP and GTP molecules.

Determine the Type of Process

Since the formation of peptide bonds and the overall assembly of proteins require an input of energy, protein biosynthesis is an endergonic process.

Conclusion

Protein biosynthesis is an endergonic process because it requires energy input to link amino acids into a protein.

Key concepts

Endergonic Process

Protein biosynthesis is an example of an endergonic process. Endergonic processes are those that require an input of energy to proceed. They are not spontaneous, meaning they need external energy to drive the reactions forward. In the context of protein biosynthesis, high-energy molecules like ATP and GTP are necessary. This is because building complex molecules from simpler ones (like amino acids into proteins) requires energy to form chemical bonds.

Amino Acids

Amino acids are the building blocks of proteins. Each amino acid has an amine group, a carboxyl group, and a unique side chain that determines its properties. During protein biosynthesis, amino acids are linked together in a specific sequence to form a polypeptide chain. The order and type of amino acids dictate the protein's structure and function. These amino acids are joined through a process that involves both transcription (copying genetic information from DNA to mRNA) and translation (decoding mRNA to build proteins).

Peptide Bonds

Peptide bonds are the chemical links that connect amino acids in a protein. These bonds form between the carboxyl group of one amino acid and the amine group of another. Forming a peptide bond releases a molecule of water and creates a longer chain of amino acids, known as a polypeptide. Peptide bonds are strong and stable, which means energy is needed to form them. This energy requirement is why protein biosynthesis is classified as an endergonic process. Without energy, the formation of peptide bonds and subsequent polypeptide chains would not be possible.

Energy Input

Energy input is essential for protein biosynthesis. The cell provides this energy mainly through ATP (adenosine triphosphate) and GTP (guanosine triphosphate). These molecules serve as energy currency within the cell. When their phosphate bonds are broken, a significant amount of energy is released, which is then used to power various cellular processes, including the formation of peptide bonds and the assembly of amino acids into proteins. Without sufficient energy input, protein synthesis cannot occur.

ATP

ATP, or adenosine triphosphate, is a critical energy carrier in cells. It provides the necessary power for numerous biochemical reactions, including those involved in protein biosynthesis. When ATP is hydrolyzed (broken down), it releases energy by converting into ADP (adenosine diphosphate) and an inorganic phosphate. This released energy is harnessed to form peptide bonds between amino acids, facilitating the construction of a polypeptide chain. ATP essentially fuels the machinery that orchestrates protein synthesis.

GTP

GTP, or guanosine triphosphate, is another molecule that supplies energy for protein biosynthesis. Like ATP, GTP is hydrolyzed to provide energy, but it specifically plays a vital role during the translation phase of protein synthesis. GTP is used to provide the energy for ribosomes to move along the mRNA strand and link amino acids together in the correct sequence. By constantly cycling through states of hydrolysis and reformation, GTP ensures the proper assembly and elongation of the growing polypeptide chain during protein biosynthesis.