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Among the several hundred million cells that comprise the [#permalink]
12 May 2011, 04:22
This post received KUDOS
Among the several hundred million cells that comprise the wondrously complex human body, and thus to be theoretically detectable in lab tests and in electron photomicrographs, a tiny fraction, no more than a few hundred, belong to a curious subclass whose luminescence has a wavelength distribution so unique that 5 it long defied explanation. Such systems luminisce strongly in the visible region of the spectrum, but some of them do so even more strongly at both shorter and longer wavelengths: in the ultraviolet region and in the infrared regions. 10 This odd distribution of luminescence is best explained by the pairing of a giant red blood cell and an intensely small white blood cell that is virtually in contact with its larger companion as the two travel around a common center. Such objects have become known as Clinging cells. On photographic plates only the giant cell can be discerned, but evidence for the existence of the 15 tiny companion has now been supplied by magnifying instruments capable of detecting ultraviolet luminescence at wavelengths that are absorbed by the body's heat and therefore cannot be detected by typical analytical instruments. The spectra of Clinging cells indicate that the giant red blood cell is surrounded by 20 very thin lipid filaments. The existence of the lipid filaments marked such objects as being unique several decades before clinical observations finally identified the lipid as the luminescence from the tiny companion white blood cell. Clinging cells also flare up in outbursts indicating the ejection of material in the form of a shell or a ring, reminiscent of the recurrent circulation of hormonal cells. Clinging cells may 25 therefore represent a transitory phase in the evolution of certain types of hormonal systems in which there is a substantial transfer of matter from the larger partner to the smaller. The exact evolutionary course that turns a typical blood cell system into a clinging one is 30 a matter of conjecture. The comparatively small number of known Clinging cells in our bodies suggests that if all binaries of modest mass normally pass through a clinging phase in their evolution, the phase must be extremely brief, perhaps as short as a millisecond.
1. The author's primary purpose in the passage is to (A) demonstrate that most hormonal systems were at one time clinging (B) dismiss current knowledge of Clinging cells as overly speculative (C) describe Clinging cells as a distinct type of cell system (D) present evidence that hormonal systems are formed from tiny white blood cells (E) compare characteristics of giant red blood cells and tiny white blood cells
2. The passage implies that Clinging cell systems differ from other hormonal systems in that the former
(A) display luminescence patterns different from those of most hormonal systems (B) contain two cells that revolve around a common center (C) possess far greater mass than other hormonal systems (D) are more common in our bodies than other hormonal systems (E) are the only hormonal systems that can be detected by electron microscopes
3. Which of the following can be inferred from the passage about "the luminescence" mentioned in line 22?
(A) It causes certain large red blood cells to appear tiny to observers. (B) It was incorrectly associated with hormonal cells in our bodies. (C) It interferes with the clarity of photographs of most hormonal systems. (D) It corresponds to the visible region of the light spectrum. (E) It could not be positively identified from photomicrograph observations.
4. According to the passage, the exchange of matter within a Clinging cell system is believed to be a process in which
(A) cell grows in mass at the expense of the other (B) the mass of each cell remains fairly stable (C) the mass of both cells declines (D) both cells absorb matter emitted by other nearby cells (E) both cells gradually return to an earlier singular state
5. The assumption that the Clinging cell phase in the evolution of some hormonal systems "must be extremely brief " (line ) is most likely based on the fact that
(A) hormones are rapidly ejected from clinging systems (B) few Clinging cells have been detected in our bodies (C) the cells in a clinging pair are in close proximity to each other (D) Clinging cells vary considerably in size from one another (E) the outbursts of Clinging cells resemble those of hormonal cells