单选题胆汁酸生成过程的限速步骤是

单选题下列哪种物质脱下的氢不进入NADH呼吸链

单选题关于变构调节的叙述哪一项是错误的

单选题糖蛋白糖链合成场所为

单选题下列对蛋白质变性后主要表现的叙述中不正确的是

单选题通过鸟氨酸循环生成尿素时，其分子中的两个氮原子一个直接来自游离的氨，另一个直接来源于( )(1998年)

单选题A．尿素B．尿酸C．肌酐D．氨基酸E．胆红素

单选题Scientists have for the first time used cloning to create human embryos that live long enough in a laboratory dish to have their stem cells harvested. The feat could set the stage for physicians to produce cells and tissues, tailored to a patient's genetic identity that can treat a wide variety of human illnesses. The accomplishment also provides a road map for how to clone a person, an even more divisive undertaking. The new work, performed in South Korea, represents "a major advance in stem cell research. It could help spur a medical revolution as important as antibiotics and vaccines", says Robert Lanza of Advanced Cell Technology (ACT), a company in Worcester, Mass., that's also investigating the promising stem cell strategy called therapeutic cloning. "However, now that the methodology is publicly available", Lanza adds, "I think it is absolutely imperative that we pass laws worldwide to prevent the technology from being abused for reproductive-cloning purposes." While some fertility doctors and a religious cult have claimed success at creating a pregnancy via cloning, they've offered no convincing proof. In contrast, the South Korean research is being reported at the meeting of the American Association for the Advancement of Science in Seattle and will appear in an upcoming Science. "This is reality," says stem cell researcher John Gearhart of Johns Hopkins University. "He4'e is a bona fide, refereed journal saying that a human embryo has been cloned and a cell line derived from it." Although ACT has not yet published a report of a cloned human blastocyst, Lanza says that the South Korean success is "consistent with our own results." Therapeutic cloning appeals to Lanza and physicians because cells made this way could have the same DNA as a patient's cells do and thus avoid rejection after they're transplanted. Seeking a compromise that would permit this strategy to be pursued, many scientists have called for legislation that would ban cloning to produce a baby but allow the creation of cloned embryos to generate stem cells for research or therapies. "The debate has been very polarized," notes bio-ethicist Laurie Zoloth of Northwestern University in Evanston.

单选题酶化学修饰调节最常见的方式是

单选题有机磷化合物中毒时抑制胆碱酯酶，此抑制属于

单选题血氨升高最主要的原因是

单选题目前基因治疗中最常用的基因载体是

单选题符合DNA结构的正确描述是

单选题肌肉中氨基酸脱氨基作用的主要方式

单选题A．丙酮酸B．谷氨酸C．仅一酮戊二酸D．草酰乙酸E．甘氨酸

单选题复制的校读功能

单选题A．丙酮酸激酶B．乳酸脱氢酶C．琥珀酸脱氢酶D．异柠檬酸脱氢酶 (2012年)

单选题脂肪酸氧化的限速酶是

单选题血糖浓度低时，脑仍能摄取葡萄糖而肝不能是因为( )(2005年)

单选题如果食物中长期缺乏植物油，将导致人体内减少的物质