BioChem Lecture 17

What is the equivalent energy stored in ATP required for nitrogen fixation?

• 31 high-energy phosphoryl bonds

• 15 high-energy phosphoryl bonds

• 50 high-energy phosphoryl bonds

• 10 high-energy phosphoryl bonds

What is the overall reaction carried out by the nitrogenase complex?

• N₂ + 8 e⁻ + 8 H⁺ → 2 NH₃ + H₂

• N₂ + 6 e⁻ + 6 H⁺ → NH₃ + H₂

• N₂ + 10 e⁻ + 10 H⁺ → 2 NH₃ + H₂

• N₂ + 4 e⁻ + 4 H⁺ → NH₃ + H₂

How many ATP molecules are required for each high-potential electron used in the nitrogenase reaction?

• 1 ATP

• 2 ATP

• 4 ATP

• 8 ATP

What happens to NH₃ in an aqueous environment at biological pH values?

• It remains as NH₃.

• It is converted to ammonium ion (NH₄⁺).

• It forms glutamate directly.

• It reacts with α-ketoglutarate.

What enzyme is responsible for the synthesis of glutamate from NH₄⁺ and α-ketoglutarate?

• Glutamine synthetase.

• Glutamate dehydrogenase.

• Carbamoyl phosphate synthetase.

• Aspartate transaminase.

What drives the amidation reaction during the synthesis of glutamine from glutamate?

• NADH oxidation

• ATP hydrolysis

• Pi release

• ADP phosphorylation

Which amino acid is derived from oxaloacetate in the citric acid cycle?

• Glutamate

• Aspartate

• Alanine

• Phenylalanine

Why is the strategy of relying on dietary intake for essential amino acids considered reasonable for humans?

• Humans are relatively low on the food chain.

• Humans are relatively high on the food chain.

• Humans can synthesize all amino acids without dietary intake.

• Humans absorb amino acids directly from the environment.

Which molecule provides the ammonium source in mammals for the formation of asparagine?

• Glutamine

• Aspartate

• Adenine

• ATP

How is the formation of asparagine from aspartate chemically analogous to the formation of glutamine?

• Both reactions involve the formation of an acyl-phosphate intermediate.

• Both reactions are amidations and require ATP hydrolysis.

• Both reactions involve the direct conversion of ATP to AMP.

• Both reactions use aspartate as the ammonium source.