暑期實戰(zhàn) 2017考研英語閱讀理解精練之肽激素

　　2017考研基礎(chǔ)階段復(fù)習(xí)基本告一段落，考生們感覺掌握的怎么樣?實踐是檢驗真理的唯一標(biāo)準(zhǔn)，動手做起來吧!下面是文都考研小編為大家準(zhǔn)備了考研英語閱讀理解：

　　考研英語閱讀理解之肽激素：

　　Until about five years ago, the very idea that peptide hormones might be made anywhere in the brain besides the hypothalamus was astounding. Peptide hormones, scientists thought, were made by endocrine glands and the hypothalamus was thought to be the brains’ only endocrine gland. What is more, because peptide hormones cannot cross the blood-brain barrier, researchers believed that they never got to any part of the brain other than the hypothalamus, where they were simply produced and then released into the bloodstream.

　　But these beliefs about peptide hormones were questioned as laboratory after laboratory found that antiserums to peptide hormones, when injected into the brain, bind in places other than the hypothalamus, indicating that either the hormones or substances that cross-react with the antiserums are present. The immunological method of detecting peptide hormones by means of antiserums, however, is imprecise. Cross-reactions are possible and this method cannot determine whether the substances detected by the antiserums really are the hormones, or merely close relatives. Furthermore, this method cannot be used to determine the location in the body where the detected substances are actually produced.

　　New techniques of molecular biology, however, provide a way to answer these questions. It is possible to make specific complementary DNA’s (c DNA’s) that can serve as molecular probes seek out the messenger RNA’s (mRNA’s) of the peptide hormones. If brain cells are making the hormones, the cells will contain these mRNA’s. If the products the brain cells make resemble the hormones but are not identical to them, then the c DNA’s should still bind to these mRNA’s, but should not bind as tightly as they would to m RNA’s for the true hormones. The cells containing these mRNA’s can then be isolated and their mRNA’s decoded to determine just what their protein products are and how closely the products resemble the true peptide hormones.

　　The molecular approach to detecting peptide hormones using cDNA probes should also be much faster than the immunological method because it can take years of tedious purifications to isolate peptide hormones and then develop antiserums to them. Roberts, expressing the sentiment of many researchers, states: “I was trained as an endocrinologist. But it became clear to me that the field of endocrinology needed molecular biology input. The process of grinding out protein purifications is just too slow.”

　　If, as the initial tests with cDNA probes suggest, peptide hormones really are made in brain in areas other than the hypothalamus, a theory must be developed that explains their function in the brain. Some have suggested that the hormones are all growth regulators, but Rosen’s work on rat brains indicates that this cannot be true. A number of other researchers propose that they might be used for intercellular communication in the brain.

　　1. Which of the following titles best summarizes the text?

　　[A] Is Molecular Biology the Key to Understanding Intercellular Communication in the Brain?

　　[B] Molecular Biology: Can Researchers Exploit Its Techniques to Synthesize Peptide Hormones?

　　[C] The Advantages and Disadvantages of the Immunological Approach to Detecting Peptide Hormones.

　　[D] Peptide Hormones: How Scientists Are Attempting to Solve Problems of Their Detection and to Understand Their Function?

　　2. The text suggests that a substance detected in the brain by use of antiserums to peptide hormones may

　　[A] have been stored in the brain for a long period of time.

　　[B] play no role in the functioning of the brain.

　　[C] have been produced in some part of the body other than the brain.

　　[D] have escaped detection by molecular methods.

　　3. According to the text, confirmation of the belief that peptide hormones are created in the brain in areas other than the hypothalamus would force scientists to

　　[A] reject the theory that peptide hormones are made by endocrine glands.

　　[B] revise their beliefs about the ability of antiserums to detect peptide hormones.

　　[C] invent techniques that would allow them to locate accurately brain cells that produce peptide hormones.

　　[D] develop a theory that account for the role played by peptide hormones in the brain.

　　4. Which of the following is mentioned in the text as a drawback of the immunological method of detecting peptide hormones?

　　[A] It cannot be used to detect the presence of growth regulators in the brain.

　　[B] It cannot distinguish between the peptide hormones and substances that are very similar to them.

　　[C] It uses antiserums that are unable to cross the blood-brain barrier.

　　[D] It involves a purification process that requires extensive training in endocrinology.

　　5. The idea that the field of endocrinology can gain from developments in molecular biology is regarded by Roberts with

　　[A] incredulity.

　　[B] derision.

　　[C] indifference.

　　[D] enthusiasm.

　　答案及解析：

　　1. 【答案】D

　　【考點解析】這是一道中心主旨題。全文從頭至尾討論的是“peptide hormones”在人體內(nèi)產(chǎn)生的部位，所以有關(guān)全文中心主旨內(nèi)容的答案應(yīng)該包含“peptide hormones”。從各段的主題句進(jìn)行分析，第一至四段主要講如何“detect”(探測)肽激素(peptide hormones)所產(chǎn)生的位置，第五段主要講有關(guān)肽激素的“function”�？梢姳绢}的正確選項應(yīng)該是D�？忌�在解題時一定要搞清楚原文所涉及的對象并且抓住每段的主題句以及它們之間的相互關(guān)系。

　　2. 【答案】C

　　【考點解析】這是一道審題定位題。根據(jù)題干中的“a substance detected”可把本題的正確選項迅速確定在第二段的尾句。該句所涉及的核心問題是“where”，所以本題的正確選項應(yīng)該是C。考生在解題時一定要迅速而準(zhǔn)確地進(jìn)行審題定位。

　　3. 【答案】D

　　【考點解析】本題是一道細(xì)節(jié)推導(dǎo)題。通過本題題干中的“peptide hormones are created in the brain in areas other than the hypothalamus”可將本題的答案信息來源迅速確定在尾段的第一句。尾段第一句主要就肽激素的“function”進(jìn)行論述，可見本題的正確選項應(yīng)該是D，選項D中的“role”就等于原文中的“function”�？忌�在解題時一定要善于抓住主句中的重要信息。

　　4. 【答案】B

　　【考點解析】這是一道句間關(guān)系題。根據(jù)本題題干中的“the immunological method”可將本題的答案信息來源迅速確定在第二段的第二句，而本題的確切答題點在第二段的第三句的后半部分。從第二段第三句的后半部分可以推導(dǎo)出本題的正確答案是B。考生在解題時一定要注意一般概括句和具體陳述句之間的相互關(guān)系。

　　5. 【答案】D

　　【考點解析】本題是一道細(xì)節(jié)推導(dǎo)題。根據(jù)本題題干中的人名“Roberts”可將本題的答案迅速確定在倒數(shù)第二段引號部分的第二句話，即“But”一詞引導(dǎo)的句子。從該句中的“needed”一詞可以看出本題的正確選項應(yīng)該是D�？忌�在解題時一定要學(xué)會深入理解原文的字面含義。

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