During de novo pyrimidine synthesis, the pyrimidine ring is assembled and then joined to phosphoribosyl pyrophosphate (PRPP), forming orotidine monophosphate. Orotidine monophosphate is next converted to uridylate, or UMP. UMP can then be converted to another pyrimidine ribonucleotide, CTP. Identify the source of each atom in the pyrimidine ring.

Which of the following is the best definition of aerobic respiration? o a. the cellular process that releases energy by breaking down glucose o b. physical activity that involves the repeated motion of large muscle groups o c. physical activity that increases heart rate and breathing rate o d. the cellular process that converts solar energy to chemical energy