D. Pyrimidine biosynthetic intermediates accumulate when SHMT-M is disrupted compared to the DiCre parental line (C) following rapamycin/glucosamine treatment (mean ±SEM). Pyrimidine biosynthetic disruption islinked to dihydroorotate dehydrogenase (DHODH) inhibition and blockage of the mitochondrial electron transport chain (mETC). Ubiquinone (Q) is the necessary electron carrier for the mETC. 