Question

1. (35 points) A scientist from Australia observed a strange yeast-like fungi species that lives in deep areas of the ocean that is predominantly nitrogen based, with very little almost no oxygen present. He did some genomic sequencing of this yeast and found that it once used to live closer to the surface of the ocean, but then began colonizing the deep sea for several hundred years. The strange thing is that when he moves this fungi species to a ocean-water like environment in his lab, they all eventually die in a few days. When these fungi were tested for respiratory capacity in their mitochondria, it was detected that they have severely down-regulated Electron Transport Chain enzymes. A. (9 points) What is the only nutrient source that these fungi most probably live off of and why? (40 words max) ANSWER: B. (8 points) What would happen if you provided these fungi TCA cycle intermediates as down-stream carbon source intermediates, by passing all metabolism before TCA cycle? (50 words max). ANSWER: C. (10 points) Explain the metabolic challenge that this fungi could have, in terms of making a very important cofactor needed for the central metabolic pathway oxidation reactions and what how you thing this organism has adapted to overcome this problem? What is this molecule that needs to be made and why? (50 words max) ANSWER: D. (8 points) How much ATP do you think this organism makes, if it goes through one pass of the central metabolic pathway, for whichever reactions are applicable? "One pass" means just once through the beginning to the end of the central metabolic pathway. Why did you choose this ATP value? (30 words max). ANSWER:

Answer 1

A. The fungi must be anaerobes , so they must be taking good amount of carbohydrate diet. Because, anaerobic respiration produces very little amount of energy. Because it produces less energy, they must be feeding more of carbohydrates only.

B.Supplying TCA cycle intermediates will not help because the fungi does not have any components of ETC. The coenzymes produced by the TCA cycle have to be carried to ETC for generating ATP. Because ETC components are not present, there is no way that the organism is going to be benefited by TCA cycle intermediates.

C. In respiratory path ways coenzymes such as NADH and FADH2 are important carriers of reducing power to ETC where they get oxidized and the flow of electrons through the ETC generates energy. When ETC is not present, converting the NADH to oxidized form is a challenge. The NADh is very important co-enzyme needed during glycolysis.

D. Because the organism is undergoing only glycolysis, it makes only 2 ATP molecules. There are 4 ATP molecules produced during the process. But 2 ATP molecules get consumed , so the net gain is only 2 ATP.