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BCH 301David Umahi Federal University of Health SciencesOct 26, 2026

BCH 301 METABOLISM OF NUCLEOTIDES AND AMINO ACIDS

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Executive Topic Summary

High-yield cheatsheet and core concepts for BCH 301.

High-Yield Exam Takeaways

  • BCH 301: Nitrogen Metabolism & Nitrogen Fixation
  • The Nitrogen Problem
  • The Nitrogen Web (Not a Simple Cycle)
  • Nitrogenase: The Only Biological N₂ Reductase
  • Assimilation of Fixed Nitrogen
  • Sources of Fixed Nitrogen
  • Memory Hooks

Sample Practice Questions (Active Recall)

Showing 3 of 65+

Q1.Which of the following best explains why molecular nitrogen ($N_2$) cannot be directly utilized by most living organisms despite comprising approximately 80% of Earth's atmosphere?

AAtmospheric $N_2$ exists predominantly as atomic nitrogen rather than molecular nitrogen
B$N_2$ is too soluble in aqueous biological environments to be accessible for reduction
CThe $N \equiv N$ triple bond has insufficient bond energy to facilitate biological reduction
DThe $N \equiv N$ triple bond has an exceptionally high bond energy of 945 kJ mol⁻¹, making it kinetically inert

Q2.How does the metabolic availability of nitrogen compare to that of phosphorus in living systems?

ABoth nitrogen and phosphorus occur predominantly as stable, unreactive gases that require biological fixation
BBoth elements require nitrogenase-catalyzed reduction before assimilation into biomolecules
CPhosphorus occurs as inorganic phosphate ($P_i$), which is metabolically available, whereas nitrogen as $N_2$ is extremely stable and unreactive
DNitrogen as $N_2$ and phosphorus as $P_2$ both possess triple bonds with similar bond energies

Q3.Which of the following best describes the relative abundance ranking of nitrogen among elements contributing to the mass of living systems?

ANitrogen ranks fourth after oxygen, hydrogen, and carbon
BNitrogen ranks third after carbon and hydrogen
CNitrogen ranks second after carbon
DNitrogen ranks fifth after phosphorus

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