Biochemistry 4th Edition by Christopher Mathews,Kensal van Holde, Dean Appling, Spencer Anthony Cahill

Exercise 8

Methyl-labeled [ 14 C] methionine at a specific activity of 2.0 milli-curies per millimole was injected into rats. Six hours later the rats were killed. Phosphatidylcholine was isolated from the liver and found to have a specific activity of 1.5 millicuries per millimole. Calculate the proportions of phosphatidylcholine synthesized by the phosphatidylserine pathway and by the pathway starting from free choline. What further information would you need for your calculated values to reflect the true rates of these processes