The hard work of you and your co-workers has resulted in the isolation of a nove
ID: 53738 • Letter: T
Question
The hard work of you and your co-workers has resulted in the isolation of a novel organism:
I .confusia. You determine that I. confusia has all the enzymes for glycolysis, can produce lactic acid as a fermentation product, has a TCA cycle, and an electron transport chain, but this ETC doesn’t use oxygen as a terminal electron acceptor. As a result, the cell only gets 2 pairs of protons pumped out per NADH2, and only 1 pair of protons pumped out per FADH2 molecule. I. confusia has a membrane bound ATPase that converts pairs of protons to ATP, and flagella turned by the proton motive force.
a)What is the net ATP yield for this organism for fermentation of glucose?
b)How much ATP is gained/lost when the organism converts 2 pyruvate molecules to lactate? What else does the cell gain from that reaction, or why is this reaction important?
c) I. confusia can grow in minimal media where arginine is the only carbon and energy source. The organism takes up arginine, converts it to a-ketoglutaric acid. What biochemical pathways would be useful when growing on this media? Make your choice from the three listed. Circle your answer(s), no partial credit
Glycolysis Fermentation TCA Cycle
d) I. confusia uses a co-transporter to move the arginine across the cytoplasmic membrane. It simultaneously moves two protons for each arginine molecule transported from the periplasm into the cytoplasm. Of course, then those protons are not available for ATP production. How much ATP does I. confusia loose if it uses two protons to transport a molecule of arginine?
e) How much ATP will be made by substrate level phospohorylation if I. confusia is consuming a molecule of arginine?
f) How many protons would I. confusia be able to pump out across the cytoplasmic membrane if it consumes a molecule of arginine?
g) Based on your calculations, could I. confusia grow on arginine minimal media if the electron acceptor is there? Why or why not?
Explanation / Answer
a) The net ATP yield from glycolysis or fermentation of glucose will be 2 ATP.
b) There will not be any gain or loss of ATP.
The reaction is important because it regenerates NAD+ for glycolysis.
c) The pathway that would be useful when growing this media will be TCA cycle.
d) Two protons are used to make one ATP. This means that I. confusia looses 1 ATP.
e) One molecule of argibnine utilizes two protons to get transported and two protons correspond to 1 ATP. This means that 1 ATP will be consumed.
f) 1 NADH from TCA cycle correspond to six protons or 3 ATP. Thus, it will be able to pump out 6 protons.
g) Since it produces net 3 ATP therefore, it will be able be able to grow on arginine mininal media if electron acceptor is present.
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