Glucose is experimentally synthesized with C-14 at carbon 1, and used as a substrate for aerobic metabolism. Where is the label at the end of glycolysis? Draw the glycolysis product with the labeled carbon circled or highlighted. Now take that glycolysis product a little farther. Where is the label after entry into the Citric acid cycle? Show your work, being sure to highlight the labeled carbon at each step.

When O2 is added to an anaerobic suspension of cells consuming glucose at a high rate, the rate of glucose consumption declines greatly as the O2 is used up and accumulation of lactate ceases. This effect, first observed by Louis Pasteur in the 1860s, is characteristic of most cells capable of both aerobic and anaerobic glucose catabolism.
a. Why does the accumulation of lactate cease after O2 is added?
b. Why does the presence of O2 decrease the rate of glucose consumption?
c. How does the onset of O2 consumption slow down the rate of glucose consumption? Explain in terms of specific enzymes.

Discuss the chemistry and function of iron in each of the following: myoglobin, cytochrome c, and the iron-sulfur proteins of mitochondrial electron transport complex.