1.
In the citrate cycle, oxaloacetate is formed from malate. Oxaloacetate is then used as the starting
substrate in another round of the citrate cycle. But oxaloacetate is also a precursor for many other
molecules. Which of the following is NOT a potential fate of the molecule oxaloacetate? Choose
one: O A. heme cofactors O B. phosphoenolpyruvate O C. citrate O D. aspartate
Solution
Ans 1 : A) heme cofactors
Heme cofactors cannot be formed out of oxaloacetate , whereas the rest all other molecules such
as aspartate , citrate and phosphoenolpyruvate can be synthesised by oxaloacetate.
Different enzymes such as aspartate transaminase , citrate synthase and phosphoenolpyruvate
carboxykinase catalyse these conversions.