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Passage64
头一次碰到考分子生物过程的，好在考的不是很细的内容．
总结：
１．个人认为这篇生物文章考过程太多，但是题目除4题外，考的还都是大面内容,不象ETS的作风．
２． 本文作不好，用杨鹏的话：＂不好伤心，痛苦和绝望＂，撕了算了ffice ffice" />
３．从GRE到GMAT是本人碰到考生物过程而非数量的第一篇．当然科学的GRE有厄尔尼诺现象．
The antigen-antibody immunological reaction used to be regarded as typical of immunological responses. Antibodies are proteins synthesized by specialized cells called plasma cells, which are formed by lymphocytes (cells from the lymph system) when an antigen, a substance foreign to the organism’s body, comes in contact with lymphocytes (这里作个总结L+AgàP合成àAb). Two important manifestations of antigen-antibody immunity are lysis, the rapid physical rupture of antigenic cells and the liberation of their contents into the surrounding medium, and phagocytosis, a process in which antigenic particles are engulfed by and very often digested by macrophages and polymorphs(Ag-Ab的两个表现：(1)L过程Ag的分裂和扩散 (2)P过程Ag被M和P消化). The process of lysis is executed by a complex and unstable blood constituent known as complement, which will not work unless it is activated by a specific antibody; the process of phagocytosis is greatly facilitated when the particles to be engulfed are coated by a specific antibody directed against them (L过程要Ab被激活，P过程要Ab被附着).
现场读完后一段的总结：L+AgàPàAb; Ag-Ab有两个过程L和P都和Ag和Ab有关
The reluctance to—abandon this hypothesis, however well it explains specific processes, impeded new research, and for many years antigens and antibodies dominated the thoughts of immunologists so completely that those immunologists overlooked certain difficulties（很重要，说明Ag-Ab有缺陷，不是完全好）. Perhaps the primary difficulty with the antigen-antibody explanation is the informational problem of how an antigen is recognized and how a structure exactly complementary to it is then synthesized. When molecular biologists discovered, moreover, that such information cannot flow from protein to protein, but only from nucleic acid to protein, the theory that an antigen itself provided the mold that directed the synthesis of an antibody had to be seriously qualified (缺陷是P到P的信息传递不对，是从NA到P. Ag本身不能使Ab合成). The attempts at qualification and the information provided by research in molecular biology led scientists to realize that a second immunological reaction is mediated through the lymphocytes that are hostile to and bring about the destruction of the antigen. This type of immunological response is called cell-mediated immunity (C-M过程).
Recent research in cell-mediated immunity has been concerned not only with the development of new and better vaccines, but also with the problem of transplanting tissues and organs from one organism to another, for although circulating antibodies play a part in the rejection of transplanted tissues, the primary role is played by cell-mediated reactions (C-M的应用和作用). During cell-mediated responses, receptor sites on specific lymphocytes and surface antigens on the foreign tissue cells form a complex that binds the lymphocytes to the tissue. Such lymphocytes do not give rise to antibody-producing plasma cells but themselves bring about the death of the foreign-tissue cells, probably by secreting a variety of substances, some of which are toxic to the tissue cells and some of which stimulate increased phagocytic activity by white blood cells of the macrophage type (C-M过程：L和Ag作用，L不产生Ab, 直接杀死Ag). Cell-mediated immunity also accounts for the destruction of intracellular parasites.
1. The author is primarily concerned with (Ag-Ab 和C-M,过程，E)
(A) proving that immunological reactions do not involve antibodies
(B) establishing that most immunological reactions involve antigens
(C) criticizing scientists who will not change their theories regarding immunology
(D) analyzing the importance of cells in fighting disease（E）
(E) explaining two different kinds of immunological reactions
2. The author argues that the antigen-antibody explanation of immunity “had to seriously qualified” (line 37) because (Ab-Ag不能解释的现象是因为P-P信息传递不成立，这时Ag不合成Ab(也就是Ag+LàPàAb不成立) E)
(A) antibodies were found to activate unstable components in the blood
(B) antigens are not exactly complementary to antibodies
(C) lymphocytes have the ability to bind to the surface of antigens
(D) antibodies are synthesized from protein whereas antigens are made from nucleic acid（E）
(E) antigens have no apparent mechanism to direct the formation of an antibody
3. The author most probably believes that the antigen-antibody theory of immunological reaction (明显部分正确，D).
(A) is wrong
(B) was accepted without evidence
(C) is unverifiable
(D) is a partial explanation（D）
(E) has been a divisive issue among scientists
4. The author mentions all of the following as being involved in antigen-antibody immunological reactions EXCEPT the (Ab形成过程：L+AgàP合(4A, 4E)àAb．
Ag-Ab过程：L过程要Ab被激活(4B)，P过程要Ab被附着(4D)）答案C 此题较难，考的太细了
(A) synthesis of a protein
(B) activation of complement in the bloodstream
(C) destruction of antibodies
(D) entrapment of antigens by macrophages（C）
(E) formation of a substance with a structure complementary to that of an antigen
5. The passage contains information that would answer which of the following questions about cell-mediated immunological reactions?
I. Do lymphocytes form antibodies during cell-mediated immunological reactions?
Such lymphocytes do not give rise to antibody-producing plasma cells(C-M过程：L和Ag作用，L不产生Ab, 直接杀死Ag)
II. Why are lymphocytes more hostile to antigens during cell-mediated immunological reactions than are other cell groups?
III. Are cell-mediated reactions more pronounced after transplants than they are after parasites have invaded the organism?
(A) I only
(B) I and II only
(C) I and III only
(D) II and III only（A）
(E) I, II, and III
6. The passage suggests that scientists might not have developed the theory of cell-mediated immunological reactions if (C-M不成立，就是Ag-Ab成立如果成立，即Ag-Ab的缺陷成立：P-P的信息传递成立，答案B)
(A) proteins existed in specific group types
(B) proteins could have been shown to direct the synthesis of other proteins
(C) antigens were always destroyed by proteins
(D) antibodies were composed only of protein（B）
(E) antibodies were the body’s primary means of resisting disease
7. According to the passage, antibody-antigen and cell-mediated immunological reactions both involve which of the following processes? 答案A
I. The destruction of antigens(都有)
II. The creation of antibodies (C-M没有)
III. The destruction of intracellular parasites(都没有)
(A) I only
(B) II only
(C) III only
(D) I and II only（A）
(E) II and III only
8. The author supports the theory of cell-mediated reactions primarily by 明显B
(A) pointing out a contradiction in the assumption leading to the antigen-antibody theory
(B) explaining how cell mediation accounts for phenomena that the antigen-antibody theory cannot account for
(C) revealing new data that scientists arguing for the antigen-antibody theory have continued to ignore
(D) showing that the antigen-antibody theory fails to account for the breakup of antigens（B）
(E) demonstrating that cell mediation explains lysis and phagocytosis more fully than the antigen-antibody theory does
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发表于 2004-4-6 09:15:00
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