Biosynthesis of proteins from amino acids is an energy driven condensation process (ÄH = + 10
kJ/mol) requiring energy input in the form of ATP. In an experiment, 0.4 mol of amino acids
reacted to give a polypeptide and some ATP was consumed.
a) explain how biosynthesis of proteins is energy-coupled to the hydrolysis of ATP.
b) calculate the amount of ATP (in moles) used in the experiment if the amount of dissipated heat
was 14.3 kJ.
a) Biosynthesis of proteins is energy-coupled to the hydrolysis of ATP through a process called ATP-dependent peptide bond formation. This process involves the use of ATP as an energy source to drive the condensation of amino acids into a polypeptide chain. The energy released from the hydrolysis of ATP is used to overcome the thermodynamic barrier of peptide bond formation, which otherwise requires an input of energy.
In this process, ATP is hydrolyzed into ADP (adenosine diphosphate) and inorganic phosphate (Pi), releasing a significant amount of energy. This energy is then utilized to facilitate the condensation of amino acids, where a peptide bond is formed between the carboxyl group of one amino acid and the amino group of another amino acid. This bond formation is thermodynamically unfavorable, as it involves the release of water and an increase in entropy. However, the energy released from ATP hydrolysis provides the necessary energy to drive this reaction forward.
b) To calculate the amount of ATP used in the experiment, you need to determine the molar ratio between the dissipated heat and the energy released from ATP hydrolysis.
The standard enthalpy change of ATP hydrolysis (ΔH) is approximately -30.5 kJ/mol. This means that for every mole of ATP hydrolyzed, 30.5 kJ of energy is released.
In the given experiment, the dissipated heat is 14.3 kJ. To calculate the amount of ATP used, you can set up a proportion using the molar ratio:
ΔH of ATP hydrolysis / Dissipated heat = Moles of ATP / Moles of dissipated heat
Substituting the values:
-30.5 kJ/mol / 14.3 kJ = X mol ATP / 1 mol dissipated heat
Rearranging the equation to solve for X (moles of ATP):
X = (-30.5 kJ/mol * 1 mol dissipated heat) / 14.3 kJ
X ≈ -2.132 moles of ATP
Since moles of ATP cannot be negative, we can conclude that approximately 2.132 moles of ATP were used in the experiment.