Chat with AIExam 15: Biosynthesis
The bacterial enzyme nitrogenase performs the reduction of N₂ gas using a large amount of energy and reducing power. Describe the nitrogen reduction steps during nitrogenase activity and write the overall reaction.
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VerifiedNitrogenase catalyzes four reduction cycles: the Fe-protein acquires electrons from an electron donor such as ferredoxin or flavodoxin, and it transfers them to the iron-molybdenum (FeMo) center. The FeMo protein binds two protons and reduces them to H₂ gas; this step consumes four ATPs. N₂ binds the enzyme, displacing H₂ at the binding site. Hydrogen then leaves the enzyme. Successive pairs of protons and electrons reduce nitrogen, with four ATPs spent each time:
Which of the following is NOT correct regarding unsaturation in certain fatty acids?
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What is the health risk of having nitrates in drinking water? What conditions favor the accumulation of nitrates and nitrites in bodies of water?
(94) VerifiedIn natural environments most nitrogen sources are subject to competition from dissimilatory metabolism. Fertilizers contain nitrogen as NH₄⁺, which can leach from agricultural soils to bodies of water where it can be oxidized to nitrate and nitrite by lithotrophs, a process known as nitrification. Nitrites can combine with hemoglobin, rendering it incapable of taking up oxygen. When infants drink water with high nitrate content, they become ill with "blue baby" syndrome, as nitrate becomes nitrite in the digestive system.
What technique was used to demonstrate that gene expression of the CO₂-concentrating mechanism (CCM) transporters is induced by low levels of CO₂? Briefly explain the basis of the technique.
(74) Many of the antibiotics and other pharmaceutical agents isolated from Streptomyces species are
(83) What types of bacteria perform the reductive pentose phosphate cycle to fix CO₂?
(83) How do ammonium and oxygen regulate the expression of nitrogen fixation genes?
(87) What kind of reaction is the formation of oxaloacetate from phosphoenolpyruvate?
(85) Which technique did Melvin Calvin use to elucidate the intermediates of phototrophic carbon fixation in the chloroplasts of Chlorella?
(88) Tryptophan is among the so-called essential amino acids for humans, as we cannot produce it ourselves. Briefly describe tryptophan biosynthesis in bacteria. Why is it so energetically expensive to synthesize this aromatic amino acid?
(72) Why do most fatty acids contain an even number of carbon atoms?
(84) The structures marked with arrows in the photo below are ________ and are used to ________. 
(85) Which of the following is NOT correct regarding the biosynthesis of purines and pyrimidines?
(68) Which of the following molecules links glycolysis with the TCA cycle, and also serves as a precursor for many biosynthetic products?
(77) How do cyanobacteria benefit from their heterocysts attracting heterotrophic bacteria?
(79) All microorganisms require all of the following for biosynthetic purposes EXCEPT
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