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单选题 The first important product of nitrogen fixation is _______, which can be used by all organisms either directly or after its conversion to other soluble compounds such as nitrites, nitrates, or amino acids
学科：Biochemistry 《生物化学》一 专业基础课（全英教学）
时间：2025-04-28 10:42:05
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题目1单选题
_________________ are derived from 3-phosphoglycerateA. Ser, Gly, and CysB. Ser, Gly, and GluC. Thr, Gly, and CysD. Ser, Glu, and Cys
题目2单选题
______________ are the nitrogen donors in a wide range of biosynthetic reactionsA. Glu and AsnB. Glu and GlyC. Glu and GlnD. Glu and Ala
题目3单选题
Certain amino acids or parts of amino acids are incorporated into the structure of purines and pyrimidines, and in one case, part of a purine ring is incorporated into an amino acid (____)A. AlaB. HisC. TyrD. Trp
题目4单选题
The nitrogen cycle is short-circuited by a group of bacteria that promote anaerobic ammonia oxidation, or anammox, a process that converts ammonia and nitrite to N2. As much as ___________ of the NH3-to-N2 conversion in the biosphere may occur through this pathway, which went undetected until the 1980sA. 30% to 50%B. 40% to 60%C. 50% to 70%D. 60% to 80%
题目5单选题
The availability of fixed nitrogen, an essential nutrient, may have limited the size of the primordial biosphere. As early cells acquired a capacity to fix atmospheric nitrogen, the biosphere expanded. Evidence for biological nitrogen fixation has been found in sedimentary rocks more than ___ billion years oldA. 2B. 2.5C. 3D. 3.5
题目6单选题
The first important product of nitrogen fixation is _______, which can be used by all organisms either directly or after its conversion to other soluble compounds such as nitrites, nitrates, or amino acidsA. NO2ˉB. ammoniaC. NO3ˉD. NH4+
题目7单选题
The N≡N triple bond in N2 is very stable, with a bond energy of _____ kJ/mol. Nitrogen fixation therefore has an extremely high activation energy, and atmospheric nitrogen is almost chemically inert under normal conditionsA. 730B. 830C. 930D. 1,030
题目8单选题
The reduction of nitrogen to ammonia is an exergonic reaction: N2 + 3H2 ® 2NH3 DG° = _____ kJ/molA. –23.5B. –33.5C. –43.5D. –50.5
题目9单选题
Ammonia is produced industrially by the Haber process (named for its inventor, Fritz Haber), which requires temperatures of _________ and nitrogen and hydrogen at pressures of tens of thousands of kilopascals (several hundred atmospheres) to provide the necessary activation energyA. 200 to 300°CB. 300 to 400°CC. 400 to 500°CD. 500 to 600°C
题目10单选题
The energy used to maintain living systems relies on the generation of proton gradients across membranes. Electrons derived from a reduced substrate are made available to electron carriers in membranes and pass through a series of electron transfers to a final electron acceptor. As a byproduct of this process, protons are released on one side of the membrane, generating the transmembrane proton gradient. The proton gradient is used to synthesize ATP or to drive other energy-requiring processes. For all eukaryotes, the reduced substrate is generally a carbohydrate (glucose or pyruvate) or a fatty acid and the electron acceptor is ________A. nitrogenB. oxygenC. carbonD. sulphur
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