EK Exam 1 Question 145

[aspiringsocialepi]

This is a specific question for anyone who has taken Examkrackers Exam 1. On question 145, the graph depicts a steady increase in plasma glycerol over time, which is attributed to the action of beta oxidation of triglycerides occurring steadily over time. This makes sense to me, but I selected answer C (which depicts glycerol rising and then falling) because glycerol can then enter glycolysis as a 3-carbon substrate. Wouldn't the action of glycerol entering glycolysis cause the levels of glycerol to increase as a lesser rate over time, and eventually decrease? I'd appreciate any clarification on why the answer selected by EK is the better answer.

 

[aalamruad]

1) You're overthinking it
2) Even if the levels of glycerol increased at a lesser rate over time, they wouldn't fall back down to their initial value (which is what option C shows) if fat oxidation continued to increase. Look at the y-axis on the second graph in Figure 2: it shows the rate of fat oxidation, not the amount of fat oxidation products, so even though some of the glycerol might be used up, it is being produced at an increasing rate, which means that its concentration in the plasma will increase (and even if they wouldn't technically increase at a constant rate, they certainly wouldn't fall to their original levels with an increasing rate of fat oxidation).