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GMAT RC CHALLENGE – 36 Hardest Official GMAT RC Passages of all time (P29/36)

GMAT-RC-CHALLENGE-P29

Tiếp tục series 36 hardest GMAT RC passages, hôm nay chúng ta hãy thử sức với bài đọc số 29 nhé. 

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Passage 29/36: 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

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Bây giờ, chúng ta cùng giải Passage 29/36 nhé!

Đáp án Passage 29/36

Summary

Para 1: Antigen-antibody immunological reaction as typical of immunological responses and the way it works

Cụ thể:

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.
Para 2: Some difficulties with antigen-antibody immunological reaction and cell-mediated immunity as a immunological response

Cụ thể:

  • 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.
Para 3: The way the cell-mediated reaction works

Cụ thể:

. 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

Main point: Describe two types of immunological response.

Câu 1: The author is primarily concerned with

Prethink: Main point = Describe two types of immunological response

Vậy đáp án đúng là E. explaining two different kinds of immunological reactions

Extra notes:

  1. criticizing scientists who will not change their theories regarding immunology

. Mặc dù ở para 2, ta có thấy type 1 – antigen-antibody theory bị qualified (limited) nhưng không có nghĩa là tác giả chỉ trích thuyết này hay những nhà khoa học giữ lập trường ủng hộ thuyết này

–> Loại

Câu 2: The author argues that the antigen-antibody explanation of immunity “had to seriously qualified” because

Prethink: Ở para 2, ta có:

  • 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.

–> Như vậy, vì các nhà khoa học phân tử phát hiện ra rằng info không thể truyền từ protein sang protein nên thuyết antigen-antibody mới bị limited (bản thân thuyết này khó giải thích được “how an antigen is recognized and how a structure exactly complementary to it is then synthesized” – preceding sentence)

Vậy đáp án đúng là E. antigens have no apparent mechanism to direct the formation of an antibody

Câu 3: The author most probably believes that the antigen-antibody theory of immunological reaction.

Prethink: Như đã phân tích ở phần Extra notes của câu 1, ta cần hiểu rằng tác giả không hề chỉ trích hay không chấp nhận type 1 – antigen-antibody theory. Chỉ là tác giả nhận thấy type này chưa giải thích được toàn bộ vấn đề mà thôi.

Ta có thể cần dùng POE như sau:

A . is wrong –> Extreme –> Loại

B . was accepted without evidence –> Para 1 giải thích rất rõ về type 1 –> Loại

C . is unverifiable –> Extreme –> Loại

D . is a partial explanation –> Giữ lại

E . has been a divisive issue among scientists –> Không có thông tin trong bài –> Loại

Vậy đáp án đúng là D. is a partial explanation

Câu 4: The author mentions all of the following as being involved in antigen-antibody immunological reactions EXCEPT the

Prethink: Đối với câu này ta sẽ có 4 đáp án có được nhắc trong bài (Loại) và 1 đáp án không được nhắc trong bài (chọn)

Ta cần dùng POE và tìm thông tin trong các paragraphs như sau”

A . synthesis of a protein

Ở para 1, ta có: 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 –> Có nhắc trong bài –> Loại

B . activation of complement in the bloodstream

  • Ở para 1, ta có: 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 –> Có nhắc trong bài –> Loại

C . destruction of antibodies –> Không tìm thấy thông tin –> Giữ lại

D . entrapment of antigens by macrophages

  • Ở para 1, ta có: phagocytosis, a process in which antigenic particles are engulfed by and very often digested by macrophages and polymorphs –> Có nhắc trong bài –> Loại

E . formation of a substance with a structure complementary to that of an antigen

  • Ở para 2, ta có: 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 –> Có nhắc trong bài

–> Loại

Vậy đáp án đúng là C. destruction of antibodies

Câu 5: The passage contains information that would answer which of the following questions about cell-mediated immunological reactions?

Prethink: Đối với câu hỏi này, ta cũng cần đi tìm câu trả lời thử cho từng câu hỏi được đề xuất như sau:

I . Do lymphocytes form antibodies during cell-mediated immunological reactions?

  • Ở para 3, ta có: 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 –> Như vậy, câu trả lời là không –> Trả lời được nên giữ lại

 

II . Why are lymphocytes more hostile to antigens during cell-mediated immunological reactions than are other cell groups?

  • Không có thông tin so sánh về mức độ hostile của lymphocytes và other cell groups với antigens during cell-mediated immunological reactions –> Loại

III . Are cell-mediated reactions more pronounced after transplants than they are after parasites have invaded the organism?

  • Không có thông tin so sánh về mức độ pronounce của cell-mediated reactions trong 2 trường hợp transplants và parasite invasion –> Loại

Vậy đáp án đúng là A. I only

Câu 6: The passage suggests that scientists might not have developed the theory of cell-mediated immunological reactions if

Prethink: Ở para 2, ta có:

  • 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.

–> Ta cũng đã biết vì các nhà khoa học phân tử phát hiện ra rằng info không thể truyền từ protein sang protein nên thuyết antigen-antibody mới bị limited và từ đó cho ra đời type 2 – cell-mediated immunity. Câu này hỏi ngược lại rằng nếu chuyện gì xảy ra thì type 2 có thể sẽ không xuất hiện? –> Đáp án cần liên quan đến: “such information cannot/can flow from protein to protein”

Vậy đáp án đúng là B. proteins could have been shown to direct the synthesis of other proteins

Câu 7: According to the passage, antibody-antigen and cell-mediated immunological reactions both involve which of the following processes?

Prethink: Ta cần xét từng phát biểu và tìm thông tin trong passage như sau:

I . The destruction of antigens

  • Para 1: 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. (antigen-antibody type)
  • Para 3: 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 type)

–> Như vậy, cả 2 loại đều có –> Giữ lại

II . The creation of antibodies

  • Para 1: 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. (antigen-antibody type)
  • cell-mediated type: lymphocytes tự tiêu diệt antigen mà không tạo antibodies (para 3)

–> Loại (chỉ có type 1 có)

III . The destruction of intracellular parasites

  • Para 3: Cell-mediated immunity also accounts for the destruction of intracellular parasites (cell-mediated type)

–> Loại (Chỉ có type 2 có)

Vậy đáp án đúng là A. I only

Câu 8: The author supports the theory of cell-mediated reactions primarily by

Prethink: Ta đã biết cấu trúc của toàn bài là:

  • Para 1: Giới thiệu loại 1
  • Para 2: Khuyết điểm của loại 1 trong việc giải thích việc hình thành antibodies –> Giới thiệu loại 2 (loại 2 không cần hình thành antibodies vẫn tiêu diệt được antigen)
  • Para 3: Một số hiện tượng mà loại 2 giải thích được nhưng loại 1 thì không

Vậy đáp án đúng là B. explaining how cell mediation accounts for phenomena that the antigen-antibody theory cannot account for.

Hẹn gặp lại các bạn trong bài chia sẻ kì tới! Mọi thắc mắc liên quan đến các đáp án sai trong từng câu hỏi, các bạn có thể để lại comments bên dưới nhé.

P/s: Bài giải gợi ý trong series này chủ yếu tập trung cải thiện phần Pre-think, tức ta luôn cố gắng hết sức để tự nghĩ trước câu trả lời đúng rồi tìm đáp án gần nhất trong 5 answer choices.

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