RC- Exercise 1
Caffeine, the stimulant in coffee, has been called “the most widely used psychoactive substance on Earth.”Synder, Daly and Bruns have recently proposed that caffeine affects behavior by countering the activity in the human brain of a naturally occurring chemical called adenosine. Adenosine normally depresses neuron firing in many areas of the brain. It apparently does this by inhibiting the release of neurotransmitters, chemicals that carry nerve impulses from one neuron to the next. Like many other agents that affect neuron firing, adenosine must first bind to specific receptors on neuronal membranes. There are at least two classes of these receptors, which have been designated A1 and A2.
Snyder et al propose that caffeine, which is structurally similar to adenosine, is able to bind to both types of receptors, which prevents adenosine from attaching there and allows the neurons to fire more readily than they otherwise would.
For many years, caffeine’s effects have been attributed to its inhibition of the production of phosphodiesterase, an enzyme that breaks down the chemical called cyclic AMP. A number of neurotransmitters exert their effects by first increasing cyclic AMP concentrations in target neurons. Therefore, prolonged periods at the elevated concentrations, as might be brought about by a phosphodiesterase inhibitor, could lead to a greater amount of neuron firing and, consequently, to behavioral stimulation. But Snyder et al point out that the caffeine concentrations needed to inhibit the production of phosphodiesterase in the brain are much higher than those that produce stimulation. Moreover, other compounds that block phosphodiesterase’s activity are not stimulants.
To buttress their case that caffeine acts instead by preventing adenosine binding, Snyder et al compared the stimulatory effects of a series of caffeine derivatives with their ability to dislodge adenosine from its receptors in the brains of mice. “In general,” they reported, “the ability of the compounds to compete at the receptors correlates with their ability to stimulate locomotion in the mouse; i.e., the higher their capacity to bind at the receptors, the higher their ability to stimulate locomotion.” Theophylline, a close structural relative of caffeine and the major stimulant in tea, was one of the most effective compounds in both regards. There were some apparent exceptions to the general correlation observed between adenosine-receptor binding and stimulation.One of these was a compound called 3-isobuty1-1-methylxanthine(IBMX), which bound very well but actually depressed mouse locomotion. Snyder et al suggest that this is not a major stumbling block to their hypothesis. The problem is that the compound has mixed effects in the brain, a not unusual occurrence with psychoactive drugs. Even caffeine, which is generally known only for its stimulatory effects, displays this property, depressing mouse locomotion at very low concentrations and stimulating it at higher ones.
Based on the Passage, answer the following questions:
1. The primary purpose of the passage is to
(A) discuss a plan for investigation of a phenomenon that is not yet fully understood
(B) present two explanations of a phenomenon and reconcile the differences between them
(C) summarize two theories and suggest a third theory that overcomes the problems encountered in the first two
(D) describe an alternative hypothesis and provide evidence and arguments that support it
(E) challenge the validity of a theory by exposing the inconsistencies and contradictions in it
2. According so Snyder et al, caffeine differs from adenosine in that caffeine
(A) stimulates behavior in the mouse and in humans, whereas adenosine stimulates behavior in humans only
(B) has mixed effects in the brain, whereas adenosine has only a stimulatory effect
(C) increases cyclic AMP concentrations in target neurons, whereas adenosine decreases such concentrations
(D) permits release of neurotransmitters when it is bound to adenosine receptors, whereas adenosine inhibits such release
(E) inhibits both neuron firing and the production of phosphodiesterase when there is a sufficient concentration in the brain, whereas adenosine inhibits only neuron firing
3. In response to experimental results concerning IBMX, Snyder et al contended that it is not uncommon for psychoactive drugs to have
(A) mixed effects in the brain
(B) inhibitory effects on enzymes in the brain
(C) close structural relationships with caffeine
(D) depressive effects on mouse locomotion
(E) the ability to dislodge caffeine from receptors in the brain
4. According to Snyder et al, all of the following compounds can bind to specific receptors in the brain EXCEPT
5. Snyder et al suggest that caffeine’s ability to bind to A1 and A2 receptors can be at least partially attributed to which of the following?
(A) The chemical relationship between caffeine and phosphodiesterase
(B) The structural relationship between caffeine and adenosine
(C) The structural similarity between caffeine and neurotransmitters
(D) The ability of caffeine to stimulate behavior
(E) The natural occurrence of caffeine and adenosine in the brain
Archaeology as a profession faces two major problems.
First, it is the poorest of the poor. Only paltry sums are available for excavating and even less is available for publishing the results and preserving the sites once excavated. Yet archaeologists deal with priceless objects every day.
Second, there is the problem of illegal excavation, resulting in museum-quality pieces being sold to the highest bidder.
I would like to make an outrageous suggestion that would at one stroke provide funds for archaeology and reduce the amount of illegal digging. I would propose that scientific archeological expeditions and governmental authorities sell excavated artifacts on the open market. Such sales would provide substantial funds for the excavation and preservation of archaeological sites and the publication of results. At the same time, they would break the illegal excavator’s grip on the market, thereby decreasing the inducement to engage in illegal activities.
You might object that professionals excavate to acquire knowledge, not money. Moreover, ancient artifacts are part of our global cultural heritage, which should be available for all to appreciate, not sold to the highest bidder. I agree. Sell nothing that has unique artistic merit or scientific value. But, you might reply, everything that comes out of the ground has scientific value. Here we part company. Theoretically, you may be correct in claiming that every artifact has potential scientific value. Practically, you are wrong.
I refer to the thousands of pottery vessels and ancient lamps that are essentially duplicates of one another. In one small excavation in Cyprus, archaeologists recently uncovered 2,000 virtually indistinguishable small jugs in a single courtyard, even precious royal seal impressions known as melekh handles have been found in abundance — more than 4,000 examples so far.
The basement of museums is simply not large enough to store the artifacts that are likely to be discovered in the future. There is not enough money even to catalogue the finds; as a result, they cannot be found again and become as inaccessible as if they had never been discovered. Indeed, with the help of a computer, sold artifacts could be more accessible than are the pieces stored in bulging museum basements. Prior to sale, each could be photographed and the list of the purchasers could be maintained on the computer A purchaser could even be required to agree to return the piece if it should become needed for scientific purposes. It would be unrealistic to suggest that illegal digging would stop if artifacts were sold in the open market. But the demand for the clandestine product would be substantially reduced. Who would want an unmarked pot when another was available whose provenance was known, and that was dated stratigraphically by the professional archaeologist who excavated it?
Based on the Passage, answer the following questions:
6. The primary purpose of the passage is to propose
(A) an alternative to museum display of artifacts
(B) a way to curb illegal digging while benefiting the archaeological profession
(C) a way to distinguish artifacts with the scientific value from those that have no such value
(D) the governmental regulation of archaeological sites
(E) a new system for cataloging duplicate artifacts
7. The author implies that all of the following statements about duplicate artifacts are true EXCEPT:
(A) A market for such artifacts already exists.
(B) Such artifacts seldom have scientific value.
(C) There is likely to be a continuing supply of such artifacts.
(D) Museums are well supplied with examples of such artifacts.
(E) Such artifacts frequently exceed in quality in comparison to those already cataloged in museum collections
8. Which of the following is mentioned in the passage as a disadvantage of storing artifacts in museum basements?
(A) Museum officials rarely allow scholars access to such artifacts.
(B) Space that could be better used for display is taken up for storage.
(C) Artifacts discovered in one excavation often become separated from each other.
(D) Such artifacts are often damaged by variations in temperature and humidity.
(E) Such artifacts’ often remain uncatalogued and thus cannot be located once they are put in storage
9. The author’s argument concerning the effect of the official sale of duplicate artifacts on illegal excavation is based on which of the following assumptions? (A) Prospective purchasers would prefer to buy authenticated artifacts.
(B) The price of illegally excavated artifacts would rise.
(C) Computers could be used to trace sold artifacts.
(D) Illegal excavators would be forced to sell only duplicate artifacts.
(E) Money gained from selling authenticated artifacts could be used to investigate and prosecute illegal excavators
10. The author anticipates which of the following initial objections to the adoption of his proposal?
(A) Museum officials will become unwilling to store artifacts.
(B) An oversupply of salable artifacts will result and the demand for them will fall.
(C) Artifacts that would have been displayed in public places will be sold to private collectors.
(D) Illegal excavators will have an even larger supply of artifacts for resale.
(E) Counterfeiting of artifacts will become more commonplace
Federal efforts to aid minority businesses began in the 1960’s when the Small Business Administration (SBA) began making federally guaranteed loans and government-sponsored management and technical assistance available to minority business enterprises. While this program enabled many minority entrepreneurs to form new businesses, the results were disappointing, since managerial inexperience, unfavorable locations, and capital shortages led to high failure rates. Even 15 years after the program was implemented, minority business receipts were not quite two percent of the national economy’s total receipts. Recently federal policymakers have adopted an approach intended to accelerate development of the minority business sector by moving away from directly aiding small minority enterprises and toward supporting larger, growth-oriented minority firms through intermediary companies. In this approach, large corporations participate in the development of successful and stable minority businesses by making use of government-sponsored venture capital. The capital is used by a participating company to establish a Minority Enterprise Small Business Investment Company or MESBIC. The MESBIC then provides capital and guidance to minority businesses that have potential to become future suppliers or customers of the sponsoring company.
MESBIC’s are the result of the belief that providing established firms with easier access to relevant management techniques and more job-specific experience, as well as substantial amounts of capital, gives those firms a greater opportunity to develop sound business foundations than does simply making general management experience and small amounts of capital available. Further, since potential markets for the minority businesses already exist through the sponsoring companies, the minority businesses face considerably less risk in terms of location and market fluctuation. Following early financial and operating problems, sponsoring corporations began to capitalize MESBIC’s far above the legal minimum of $500,000 in order to generate sufficient income and to sustain the quality of management needed. MESBIC’s are now emerging as increasingly important financing sources for minority enterprises.
Ironically, MESBIC staffs, which usually consist of Hispanic and Black professionals, tend to approach investments in minority firms more pragmatically than do many MESBIC directors, who are usually senior managers from sponsoring corporations. The latter often still think mainly in terms of the “social responsibility approach” and thus seem to prefer deals that are riskier and less attractive than normal investment criteria would warrant. Such differences in viewpoint have produced uneasiness among many minority staff members, who feel that minority entrepreneurs and businesses should be judged by established business considerations. These staff members believe their point of view is closer to the original philosophy of MESBIC’s and they are concerned that, unless a more prudent course is followed, MESBIC directors may revert to policies likely to re-create the disappointing results of the original SBA approach.
Based on the Passage, answer the following questions:
11. Which of the following best states the central idea of the passage?
(A) The use of MESBIC’s for aiding minority entrepreneurs seems to have greater potential for success than does the original SBA approach.
(B) There is a crucial difference in point of view between the staff and directors of some MESBIC’s.
(C) After initial problems with management and marketing, minority businesses have begun to expand at a steady rate.
(D) Minority entrepreneurs wishing to form new businesses now have several equally successful federal programs on which to rely.
(E) For the first time since 1960, large corporations are making significant contributions to the development of minority businesses
12. According to the passage, the MESBIC approach differs from the SBA approach in that MESBIC’s
(A) seek federal contracts to provide markets for minority businesses
(B) encourage minority businesses to provide markets for other minority businesses
(C) attempt to maintain a specified rate of growth in the minority business sector
(D) rely on the participation of large corporations to finance minority businesses
(E) select minority businesses on the basis of their location
13. Which of the following does the author cite to support the conclusion that the results of the SBA program were disappointing?
(A) The small number of new minority enterprises formed as a result of the program
(B) The small number of minority enterprises that took advantage of the management and technical assistance offered under the program
(C) The small percentage of the nation’s business receipts earned by minority enterprises following the programs, implementation.
(D) The small percentage of recipient minority enterprises that were able to repay federally guaranteed loans made under the program
(E) The small number of minority enterprises that chose to participate in the program
14. Which of the following statements about the SBA program can be inferred from the passage?
(A) The maximum term for loans made to recipient businesses was 15 years.
(B) Business loans were considered to be more useful to recipient businesses than was management and technical assistance.
(C) The anticipated failure rate for recipient businesses was significantly lower than the rate that actually resulted.
(D) Recipient businesses were encouraged to relocate to areas more favorable for business development.
(E) The capitalization needs of recipient businesses were assessed and then provided for adequately
15. The author’s primary objective in the passage is to
(A) disprove the view that federal efforts to aid minority businesses have been ineffective
(B) explain how federal efforts to aid minority businesses have changed since the 1960’s
(C) establish a direct link between the federal efforts to aid minority businesses made before the 1960’s and those made in the 1980’s
(D) analyze the basis for the belief that job-specific experience is more useful to minority businesses than is general management experience
(E) argue that the “social responsibility approach” to aiding minority businesses is superior to any other approach