Fidelity of protein synthesis The average mass of proteins...

Fidelity of protein synthesis The average mass of proteins in the cell is 30,000 Da, and the average mass of an amino acid is 120 Da. In eukaryotic cells, the translation rate for a single ribosome is roughly 40 amino acids per second. (a) The largest known polypeptide chain made by any cell is titin. It is made by muscle cells and has an average weight of $3 \times 10^{6}$ Da. Estimate the translation time for titin and compare it with that of a typical protein. (b) Protein synthesis is very accurate: for every 10,000 amino acids joined together, only one mistake is made. What is the probability of an error occurring for one amino acid addition? What fraction of average sized proteins are synthesized error-free?

Fidelity of protein synthesis
The average mass of proteins in the cell is 30,000 Da, and the average mass of an amino acid is 120 Da. In eukaryotic cells, the translation rate for a single ribosome is roughly 40 amino acids per second.
(a) The largest known polypeptide chain made by any cell is titin. It is made by muscle cells and has an average weight of $3 \times 10^{6}$ Da. Estimate the translation time for titin and compare it with that of a typical protein.
(b) Protein synthesis is very accurate: for every 10,000 amino acids joined together, only one mistake is made. What is the probability of an error occurring for one amino acid addition? What fraction of average sized proteins are synthesized error-free?

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Key Concepts

Polypeptide Chain Length Estimation

This involves determining the number of amino acids in a protein based on its molecular weight and the average mass of an amino acid. Estimating chain length is critical for linking molecular size to biological function and translation duration.

Protein Synthesis Fidelity

Fidelity in protein synthesis pertains to the accuracy with which ribosomes incorporate the correct amino acids during translation. High fidelity is vital because even small errors can result in malfunctioning proteins, affecting cell viability and function.

Translation Rate

This concept refers to the speed at which ribosomes add amino acids to a growing polypeptide chain, typically measured in amino acids per second. It is essential for estimating how long protein synthesis takes and for understanding cellular efficiency in producing proteins.

Probability and Error Propagation in Synthesis

This concept addresses how to calculate the likelihood of mistakes during each step of amino acid addition and the cumulative impact on the entire polypeptide chain. It uses basic probability principles to estimate the fraction of proteins that remain error-free over many synthesis events.

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