9. Suppose you discovered a mutant eukaryotic organism whose glycolytic pathway
ID: 192285 • Letter: 9
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9. Suppose you discovered a mutant eukaryotic organism whose glycolytic pathway was shorter because of the presence of a new enzyme catalyzing the reaction below. Would shortening the glycolytic pathway in this way benefit the cell? Explain your answer. (Note: Pay attention to what happens between the indicated substrate and product in the reaction below.) [10 pts) NAD' NADHH Glyceraldehyde 3-phosphale+H 10. Oxidation-reduction reactions are essential and in abundance in cellular metabolism. [15 pts What family of enzymes catalyzes these oxidation-reduction reactions? a. b. For each of the metabolic transformations below, determine whether oxidation or reduction has occurred. (You can simply write it next to the picture.) (a) CH-H Methanol Formaldehyde Formaldehyde Formate +H Carbon dioxideFormateExplanation / Answer
9. Glycolysis involves conversion of glucose to pyruvate and involves 10 steps. There is production of 4 ATP and utilization of 2 ATP, resulting in a net gain of 2 ATP.
Normal reactions that occur during glycolysis are:
Glyceraldehyde-3 phosphate + NAD-----> 1-3 Bisphosphoglycerate + NADH
1-3 Bisphosphoglycerate+ ADP-------> 3-phosphoglycerate + ATP
However, the mutant enzyme bypasses the ATP synthesis step of formation of 3 phosphoglycerate from 1, 3 Bisphosphoglycerate, as it directly converts glyceraldehyde-3 phosphate to 3 phosphoglycerate.
There is loss of 2 ATP molecules due to this reduced step. Hence, the gain of ATP after glycolysis in the cell is 4-2-2= 0.
Under aerobic condition, energy is still generated from NADH. Net gain of ATP after aerobic respiration (glycolysis, TCA and electron transport chain) in this condition is 38-2=36 ATP. This energy will help the cell to survive under aerobic condition.
However, in anaerobic conditions, this mutant enzyme will be fatal to the cell, as no ATP is formed after glycolysis (2-2=0). There is no TCA and electron transport chain operational. Further, NADH is utilized in conversion of pyruvate to lactate (or other molecules). The anaerobic condition is fatal to the cell as no NADH is available for energy generation.
10a. Oxidation-reduction reactions involved transfer of electrons, hydrogen, or oxygen between species. During oxidation, there is loss of electrons and hydrogen or gain of oxygen. Reduction reactions involved a gain of electrons and hydrogen or loss of oxygen.
The reaction can be summarized as
Ared + Box----> Aox + Bred
Oxidoreductases are enzymes that catalyze oxidation-reduction reactions.
They are of 4 types depending on electron acceptor:
a) Oxidases, which utilize oxygen as electron acceptor but does not incorporate oxygen in the substrate.
b) Dehydrogenases, which utilize other molecules such as NAD+, NADP+ etc as electron acceptors.
c) Oxygenases, which utilize oxygen as electron acceptor and incorporate it in the substrate.
d) Peroxidases, which utilize hydrogen peroxide as electron acceptor.
10b.
a. Methanol is oxidized to formaldehyde. There is removal of two hydrogen atoms from methanol to form formaldehyde. This conversion leads to formation of C=0 group.
Right option is oxidation.
b) Formaldehyde is oxidized to form formate. There is gain of oxygen in formaldehyde (mostly from water, not shown in diagram). Hydrogen is released as a proton.
Right option is oxidation.
c) Carbon dioxide is reduced to formate. There is addition of hydrogen to oxygen in formation of formate.
Right option is reduction.
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