Q15 - Amino Acid Carbon Labelling Through the Krebs Cycle
Amino acids resulting from the degradation of proteins can be further metabolized by conversion to intermediates of the citric acid cycle. The following labelled amino acids are obtained by degradation of a labelled protein. The Krebs cycle is below. Note that most alpha-amino acids can be directly converted into their corresponding alpha-keto acid by transamination reaction as also shown below.
Figure 1.
Figure 2.
Using the information and data, determine which of the statements are true or which are false.
A. Upon introduction of the aspartate into the Krebs cycle, label will first appear in oxaloacetate.
B. Upon introduction of the alanine into the Krebs cycle, label will first appear in citrate.
C. Labelled alanine will yield 14-CO2 during the first turn of the cycle.
D. Labelled glutamate will yield 14-CO2 in the second turn of the cycle.
Question reproduced from IBO 2018, Theoretical Paper 1, licensed under CC BY-NC-SA 4.0 - attributed to the International Biology Olympiad. Open the full exam PDF · Community solutions (unofficial)