Question

The following questions should take about an hour to do:

04. I feed mice with radiolabeled fatty acids. After a period of starvation, I then measure the amount of radiolabeled glucose present. MOST LIKELY, will there be radiolabeled glucose present in these mice? Explain your answer, using the metabolic pathways that we have discussed in class.

Answer 1

1. When the acetyl-coenzyme produced during the fatty acid oxidation increases, it combines to form ketone bodies. In the starvation period, or in the absence of glucose, the brain utilizes the ketone bodies as a source of energy. The ketone bodies breakdown into acetyl coenzyme (acetyl-CoA). The acetyl CoA enters the citric acid cycle to produce energy. Formation of radiolabeled glucose does not take place in the production of energy from ketone bodies or radiolabelled fatty acid.
2. Methotrexate is a drug used in the treatment of cancer. It works on the principle of competitive inhibition of enzymes. It inhibits the production of the enzyme dihydrofolate reductase, which participates in the synthesis of tetrahydrofolate. Tetrahydrofolate act as a cofactor in the synthesis of nucleic acid and amino acids. According to the graph, methotrexate is inhibiting the growth of methotrexate sensitive cancer cell by the inhibition of dihydrofolate enzyme. The methotrexate most likely is not able to inhibit the dihydrofolate in melanoma cells, thus, the enzyme elutes earlier in affinity column. As the enzyme dihydrofolate may have degraded in methotrexate sensitive cells, they are eluting later in affinity column.