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Zorluk: OrtaPlant Science and Agricultural Technology

Consider the following statements regarding biological nitrogen fixation in legume root nodules:

1. The enzyme nitrogenase, which reduces atmospheric nitrogen (N2N_2) to ammonia (NH3NH_3), is irreversibly inactivated in the presence of molecular oxygen.
2. Leghaemoglobin acts as an oxygen scavenger that regulates free oxygen concentration inside root nodules to protect nitrogenase while sustaining bacteroid cellular respiration.

Which of the statements given above is/are correct?

  1. A
    1 only
  2. B
    2 only
  3. Both 1 and 2Cevap
  4. D
    Neither 1 nor 2

Cevap

Both statements 1 and 2 are correct.
Both statements are correct. The nitrogenase enzyme requires strictly microaerophilic or anaerobic conditions because molecular oxygen causes irreversible damage to its iron-sulfur clusters. To solve this oxygen paradox, legumes synthesize leghaemoglobin (the globin protein produced by the plant host and heme group by the bacterial symbiont), which buffers free oxygen concentrations at extremely low levels while maintaining a steady flux to bacteroid mitochondria.

Adım Adım Çözüm

1
Analyze Statement 1 regarding Nitrogenase enzyme sensitivity.
Nitrogenase contains iron-molybdenum protein complexes that undergo rapid denaturation when exposed to free molecular oxygen (O2O_2), making anaerobic conditions mandatory for its activity.
Verify biochemical properties of the nitrogen-fixing enzyme.
2
Analyze Statement 2 regarding Leghaemoglobin functionality.
Leghaemoglobin has a very high affinity for oxygen. It binds free oxygen in the nodule cytoplasm, keeping oxygen partial pressure extremely low to safeguard nitrogenase, while efficiently delivering bound oxygen to Rhizobium bacteroids for ATP generation via oxidative phosphorylation.
Verify physiological mechanism of the oxygen carrier protein in root nodules.
3
Synthesize the correctness of both statements.
Both Statement 1 and Statement 2 accurately describe essential requirements and adaptations for symbiotic nitrogen fixation.
Select the option that confirms both statements.

Anahtar Kavram

Symbiotic Nitrogen Fixation and Oxygen Paradox in Root Nodules
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Konular

Plant Science and Agricultural Technology

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