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【单选题】
若 表示双曲线,则k的范围是()A.
-1
B.
k
C.
k>1
D.
k1
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举一反三
【多选题】The characteristics of biological oxidation are( )
A.
are carried out under conditions containing water. Near neutral pH, and mild
B.
is carried out under the catalysis of an enzyme
C.
Gradual release of energy during oxidation and a considerable portion of it is stored in the form of ATP
D.
The formation of water is the oxidative synthesis of hydrogen and air in the matter
【判断题】During ATP synthesis, protons move “down” their electrochemical gradient through the F0 complex of ATP synthase
A.
正确
B.
错误
【简答题】市场上常见的移动VR设备有哪些?
【单选题】During photophosphorylation, at least eight photons must be absorbed to drive ___ electrons from H 2 O to NADPH (one photon per electron at each reaction center). The energy in eight photons of visibl...
A.
2
B.
4
C.
6
D.
8
【简答题】搜索国内主要招聘网站,了解有关外贸电商或跨境电商的相关职位及从事这一行业应具备的素质与能力。
【单选题】An impending myocardial infarction was successfully averted by thrombolytic(clot-dissolving) therapy in a 55-year-old man. Which of the following biochemical events most likely occurred during the per...
A.
Decreased hydrogen ion concentration
B.
Increase in oxidative phosphorylation
C.
Loss of intracellular Na+ and water
D.
Stimulation of the ATP synthesis
E.
Stimulation of anaerobic glycolysis and glycogenolysis
【单选题】The cellular pools of nucleotides (other than ATP) are quite small, perhaps _____ or less of the amounts required to synthesize the cell’s DNA. Therefore, cells must continue to synthesize nucleotides...
A.
0.1%
B.
0.5%
C.
1%
D.
2.5%
【多选题】How do cells construct the purine ring of inosinate (IMP) during d e novo synthesis of purine nucleotides?
A.
In the first committed step of the pathway, an amino group donated by glutamine is attached at C-1 of PRPP. The resulting 5-phosphoribosylamine is highly unstable, with a half-life of 30 seconds at pH 7.5. The purine ring is subsequently built up on this structure.
B.
The second step is the addition of three atoms from glycine. An ATP is consumed to activate the glycine carboxyl group (in the form of an acyl phosphate) for this condensation reaction. The added glycine amino group is then formylated by N 10 -formyltetrahydrofolate, and a nitrogen is contributed by glutamine, before dehydration and ring closure yield the five-membered imidazole ring of the purine nucleus, as 5-aminoimidazole ribonucleotide.
C.
At this point, three of the six atoms needed for the second ring in the purine structure are in place. To complete the process, a carboxyl group is first added. This carboxylation is unusual in that it does not require biotin, but instead uses the bicarbonate generally present in aqueous solutions. A rearrangement transfers the carboxylate from the exocyclic amino group to position 4 of the imidazole ring. In higher eukaryotes, including humans, the 5-aminoimidazole ribonucleotide product of step 5 is carboxylated directly to carboxyaminoimidazole ribonucleotide in one step instead of two. The enzyme catalyzing this reaction is AIR carboxylase.
D.
Aspartate now donates its amino group in two steps: formation of an amide bond, followed by elimination of the carbon skeleton of aspartate (as fumarate). The final carbon is contributed by N 10 -formyltetrahydrofolate, and a second ring closure takes place to yield the second fused ring of the purine nucleus. The first intermediate with a complete purine ring is inosinate (IMP).
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