As people age, their cells become less efficient and

　　less able to replace damaged components. At the same

　　time their tissues stiffen. For example, the lungs and the

　　heart muscle expand less successfully, the blood vessels

　　(5) become increasingly rigid, and the ligaments and tendons

　　tighten.

　　Few investigators would attribute such diverse effects

　　to a single cause. Nevertheless, researchers have discov-

　　ered that a process long known to discolor and toughen

　　(10)foods may also contribute to age- related impairment of

　　both cells and tissues. That process is nonenzymatic

　　glycosylation, whereby glucose becomes attached to pro-

　　teins without the aid of enzymes. When enzymes attach

　　glucose to proteins (enzymatic glycosylation), they do so

　　(15)at a specific site on a specific protein molecule for a

　　specific purpose. In contrast, the nonenzymatic process

　　adds glucose haphazardly to any of several sites along

　　any available peptide chain within a protein molecule.

　　This nonenzymatic glycosylation of certain proteins

　　(20)has been understood by food chemists for decades,

　　although few biologists recognized until recently that the

　　same steps could take place in the body. Nonenzymatic

　　glycosylation begins when an aldehyde group (CHO) of

　　glucose and an amino group (NH2) of a protein are

　　(25)attracted to each other. The molecules combine, forming

　　what is called a Schiff base within the protein. This com-

　　bination is unstable and quickly rearranges itself into a

　　stabler, but still reversible, substance known as an

　　Amadori product.

　　(30) If a given protein persists in the body for months or

　　years, some of its Amadori products slowly dehydrate and

　　rearrange themselves yet again, into new glucose-derived

　　structures. These can combine with various kinds of mol-

　　ecules to form irreversible structures named advanced

　　(35)glycosylation end products (AGE's). Most AGE's are

　　yellowish brown and fluorescent and have specific spec-

　　trographic properties. More important for the body, many

　　are also able to cross-link adjacent proteins, particularly

　　ones that give structure to tissues and organs. Although

　　(40)no one has yet satisfactorily described the origin of all

　　such bridges between proteins, many investigators agree

　　that extensive cross-linking of proteins probably contrib-

　　utes to the stiffening and loss of elasticity characteristic

　　of aging tissues.

　　(45) In an attempt to link this process with the develop-

　　ment of cataracts (the browning and clouding of the lens

　　of the eye as people age), researchers studied the effect

　　of glucose on solutions of purified crystallin, the major

　　protein in the lens of the eye. Glucose-free solutions

　　(50) remained clear, but solutions with glucose caused the

　　proteins to form clusters, suggesting that the molecules

　　had become cross-linked. The clusters diffracted light,

　　making the solution opaque. The researchers also

　　discovered that the pigmented cross-links in human

　　(55)cataracts have the brownish color and fluorescence

　　characteristic of AGE's. These data suggest that

　　nonenzymatic glycosylation of lens crystallins may

　　contribute to cataract formation.

　　17.With which of the following statements concerning

　　the stiffening of aging tissues would the author most

　　likely agree?

　　(A) It is caused to a large degree by an increased

　　rate of cell multiplication.

　　(B) It paradoxically both helps and hinders the

　　longevity of proteins in the human body.

　　(C) It can be counteracted in part by increased

　　ingestion of glucose-free foods.

　　(D) It is exacerbated by increased enzymatic

　　glycosylation.

　　(E) It probably involves the nonenzymatic glycosyla-

　　tion of proteins.

　　18. According to the passage, which of the following

　　statements is true of the process that discolors and

　　toughens foods?

　　(A) It takes place more slowly than glycosylation in

　　the human body.

　　(B) It requires a higher ratio of glucose to protein

　　than glycosylation requires in the human body.

　　(C) It does not require the aid of enzymes to attach glucose to protein.

　　(D) It proceeds more quickly when the food proteins have a molecular structure similar to that of crystallin proteins.

　　(E) Its effectiveness depends heavily on the amount of environmental moisture.

　　19. According to the passage, which of the following is characteristic of enzymatic glycosylation of proteins?

　　(A) AGE's are formed after a period of months or years.

　　(B) Proteins affected by the process are made unstable.

　　(C) Glucose attachment impairs and stiffens tissues.

　　(D) Glucose is attached to proteins for specific purposes.

　　(E) Amino groups combine with aldehyde groups to form Schiff bases.

　　20. According to the passage, which of the following statements is true of Amadori products in proteins?

　　(A) They are more plentiful in a dehydrated environment.

　　(B) They are created through enzymatic glycosylation.

　　(C) They are composed entirely of glucose molecules.

　　(D) They are derived from Schiff bases.

　　(E) They are derived from AGE's

　　21. Which of the following best describes the function of the third paragraph of the passage (lines 19-29)?

　　(A) It offers evidence that contradicts the findings described in the first two paragraphs.

　　(B) It presents a specific example of the process discussed in the first two paragraphs.

　　(C) It explains a problem that the researchers mentioned in the second paragraph have yet to solve.

　　(D) It evaluates the research discoveries described in the previous paragraph.

　　(E) It begins a detailed description of the process introduced in the previous two paragraphs.

　　22. The passage suggests that which of the following would be LEAST important in determining whether nonenzymatic glycosylation is likely to have taken place in the proteins of a particular tissue?

　　(A) The likelihood that the tissue has been exposed to free glucose

　　(B) The color and spectrographic properties of structures within the tissue.

　　(C) The amount of time that the proteins in the tissue have persisted in the body

　　(D) The number of amino groups within the proteins in the tissue

　　(E) The degree of elasticity that the tissue exhibits

　　23. If the hypothesis stated in lines 56-58 is true, it can be inferred that the crystallin proteins in the lenses of people with cataracts

　　(A) have increased elasticity

　　(B) do not respond to enzymatic glycosylation

　　(C) are more susceptible to stiffening than are

　　other proteins

　　(D) are at least several months old

　　(E) respond more acutely than other proteins to changes in moisture levels

　　Writing of the Iroquois nation, Smith has argued that through the chiefs' council, tribal chiefs traditionally maintained complete control over the political affairs of both the Iroquois tribal league and the individual tribes

　　(5) belonging to the league, whereas the sole jurisdiction over religious affairs resided with the shamans.

　　According to Smith, this division was maintained until the late nineteenth century, when the dissolution of the chiefs' council and the consequent diminishment of the

　　(10) chiefs' political power fostered their increasing involvement in religious affairs.

　　However, Smith fails to recognize that this division of power between the tribal chiefs and shamans was not actually rooted in Iroquois tradition; rather, it resulted

　　(15) from the Iroquois' resettlement on reservations early in the nineteenth century. Prior to resettlement, the chiefs'council controlled only the broad policy of the tribal league; individual tribes had institutions― most important, the longhouse to govern their own affairs. In the

　　(20) longhouse, the tribe's chief influenced both political and religious affairs.

　　24.The primary purpose of the passage is to

　　(A) question the published conclusions of a scholar concerning the history of the Iroquois nation

　　(B) establish the relationship between an earlier scholar's work and new anthropological research

　　(C) summarize scholarly controversy concerning an incident from Iroquois history.

　　(D) trace two generations of scholarly opinion concerning Iroquois social institutions

　　(E) differentiate between Iroquois political practices and Iroquois religious practices

　　25. It can be inferred that the author of the passage regards Smith's argument as

　　(A) provocative and potentially useful, but flawed by poor organization

　　(B) eloquently presented, but needlessly inflammatory

　　(C) accurate in some of its particulars, but inaccurate with regard to an important point.

　　(D) historically sound, but overly detailed and redundant

　　(E) persuasive in its time, but now largely outdated

　　26. The author of the passage implies that which of the following occurred after the Iroquois were resettled on reservations early in the nineteenth century?

　　(A) Chiefs became more involved in their tribes'religious affairs.

　　(B) The authority of the chiefs' council over the affairs of individual tribes increased.

　　(C) The political influence of the Iroquois shamans was diminished.

　　(D) individual tribes coalesced into the Iroquois tribal league.

　　(E) The longhouse because a political rather than a religious institution.

　　27. Which of the following best expresses an opinion presented by the author of the passage?

　　(A) Smith has overstated the importance of the political role played by Iroquois tribal chiefs in the nineteenth century.

　　(B) Smith has overlooked the fact that the Iroquois rarely allowed their shamans to exercise political authority.

　　(C) Smith has failed to explain why the chiefs'council was dissolved late in the nineteenth century.

　　(D) Smith has failed to acknowledge the role prior to the nineteenth century of the Iroquois tribal chiefs in religious affairs.

　　(E) Smith has failed to recognize that the very structure of Iroquois social institutions reflects religious beliefs.

　　28. DRONE:

　　(A) behave bestially

　　(B) decide deliberately

　　(C) err intentionally

　　(D) speak animatedly

　　(E) plan inefficiently

　　29.CERTAINTY:

　　(A) obstinacy

　　(B) impetuosity

　　(C) recklessness

　　(D) indecision

　　(E) indifference

　　30. MORIBUND:

　　(A) fully extended

　　(B) automatically controlled

　　(C) loosely connected

　　(D) completely dispersed

　　(E) increasingly vital