Two Rcs from My side:
(From Some GMAT material
)
RC1:
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. 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. 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.
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. 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. 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.
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. 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. Cell-mediated immunity also accounts for the destruction of intracellular parasites.
1. The author is primarily concerned with
(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) 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
(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) 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.
(A) is wrong
(B) was accepted without evidence
(C) is unverifiable
(D) is a partial explanation
(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
(A) synthesis of a protein
(B) activation of complement in the bloodstream
(C) destruction of antibodies
(D) entrapment of antigens by macrophages
(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?
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
(E) I, II, and III
6. The passage suggests that scientists might not have developed the theory of cell-mediated immunological reactions if
(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
(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?
I. The destruction of antigens
II. The creation of antibodies
III. The destruction of intracellular parasites
(A) I only
(B) II only
(C) III only
(D) I and II only
(E) II and III only
8. The author supports the theory of cell-mediated reactions primarily by
(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
(E) demonstrating that cell mediation explains lysis and phagocytosis more fully than the antigen-antibody theory does
RC2:
The founders of the Republic viewed their revolution primarily in political rather than economic or social terms. And they talked about education as essential to the public good—a goal that took precedence over knowledge as occupational training or as a means to self-fulfillment or self-improvement.
Over and over again the Revolutionary generation, both liberal and conservative in outlook, asserted its conviction that the welfare of the Republic rested upon an educated citizenry and that schools, especially free public schools, would be the best means of educating the citizenry in civic values and the obligations required of everyone in a democratic republican society. All agreed that the principal ingredients of a
civic education were literacy and the inculcation of patriotic and moral virtues, some others adding the study of history and the study of principles of the republican government itself.
The founders, as was the case of almost all their successors, were long on exhortation and rhetoric regarding the value of civic education, but they left it to the textbook writers to distill the essence of those values for school children. Texts in American history and government appeared as early as the 1790s. The textbook writers turned out to be very largely of conservative persuasion, more likely Federalist in outlook than Jeffersonian, and almost universally agreed that political virtue must rest upon moral and religious precepts. Since most textbook writers were New Englander, this meant that the texts were infused with Protestant and, above all, Puritan outlooks.
In the first half of the Republic, civic education in the schools emphasized the inculcation of civic values and made little attempt to develop participatory political skills. That was a task left to incipient political parties, town meetings, churches and the coffee or ale houses where men gathered for conversation. Additionally as a reading of certain Federalist papers of the period would demonstrate, the press probably did more to disseminate realistic as well as partisan knowledge of government than the schools. The goal of education, however, was to achieve a higher form of
unum (one out of many used on the Great Sealof the U.S. and on several U.S. coins)for the new Republic. In the middle half of the nineteenth century, the political values taught in the public and private schools did not change substantially from those celebrated in the first fifty years of the Republic. In the textbooks of the day their rosy hues if anything became golden. To the resplendent values of liberty, equality, and a benevolent Christian morality were now added the middle-class virtues-especially of New England-of hard work, honesty and integrity, the rewards of individual effort, and obedience to parents and legitimate authority. But of all the political values taught in school, patriotism was preeminent; and whenever teachers explained to school children why they should love their country above all else, the idea of liberty assumed pride of place.
1. The passage deals primarily with the
(A) content of early textbooks on American history and government
(B) role of education in late eighteenth-and early to mid-nineteenth-century America
(C) influence of New England Puritanism on early American values
(D) origin and development of the Protestant work ethic in modern America
(E) establishment of universal free public education in America
2. According to the passage, the founders of the Republic regarded education primarily as
(A) a religious obligation
(B) a private matter
(C) an unnecessary luxury
(D) a matter of individual choice
(E) a political necessity
3. The author states that textbooks written in the middle part of the nineteenth century
(A) departed radically in tone and style from earlier textbooks
(B) mentioned for the first time the value of liberty
(C) treated traditional civic virtues with even greater reverence
(D) were commissioned by government agencies
(E) contained no reference to conservative ideas
4. Which of the following would LEAST likely have been the subject of an early American textbook?
(A) basic rules of English grammar
(B) the American Revolution
(C) patriotism and other civic virtues
(D) vocational education
(E) principles of American government
5. The author’s attitude toward the educational system she discusses can best be described as
(A) cynical and unpatriotic
(B) realistic and analytical
(C) pragmatic and frustrated
(D) disenchanted and bitter
(E) idealistic and naive
6. The passage provides information that would be helpful in answering which of the following questions?
(A) Why were a disproportionate share of early American textbooks written by New England authors?
(B) Was the Federalist party primarily a liberal or conservative force in early American politics?
(C) How many years of education did the founders believe were sufficient to instruct young citizens in civic virtue?
(D) What were that names of some of the Puritan authors who wrote early American textbooks?
(E) Did most citizens of the early Republic agree with the founders that public education was essential to the welfare of the Republic?
7. The author implies that an early American Puritan would likely insist that
(A) moral and religious values are the foundation of civic virtue
(B) textbooks should instruct students in political issues of vital concern to the community
(C) textbooks should give greater emphasis to the value of individual liberty than to the duties of patriotism
(D) private schools with a particular religious focus are preferable to public schools with no religious instruction
(E) government and religion are separate institutions and the church should not interfere in political affairs
8. According to the passage citizens of the early Republic learned about practical political matters in all of the following ways EXCEPT
(A) reading newspapers
(B) attending town meetings
(C) conversing about political matters
(D) reading textbooks
(E) attending church
Will post the answers tomorrow
Re: CAT 2007 - VA/RC : The last lap!! -
10-10-2007, 06:56 PM
