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2014 ‫מועד פברואר‬ - 41 - ‫ פרק ראשון‬- ‫ אנגלית‬

Text II (Questions 18-22)

(1) Antibiotics are a group of chemical substances produced by certain types of
micro-organisms. In low concentrations, they can kill or stop the growth of other

micro-organisms which cause disease in humans, animals and plants.

Antibiotic research began as a result of Sir Alexander Fleming's accidental
(5) discovery of the effects of Penicillium mould in 1928. He noticed that something was

contaminating a laboratory culture of staphylococci, the bacteria which cause blood
poisoning. A mould colony had gotten into the culture and had begun producing a
substance which had spread and killed the surrounding staphylococci. Tests showed
that this substance could also kill or inhibit the growth of a number of other kinds of
(10) disease-causing bacteria. This was a monumental discovery. For several years
researchers were unable to identify the active chemical agent in the mould responsible
for killing the bacteria. Eventually this substance, penicillin, was isolated in very small
quantities. Clinical trials demonstrated its potential medical value and opened up a new
field of medical research. However, before the substance could be made available for
(15) widespread use, methods for obtaining it in sufficient quantities had to be developed.

World War II provided the impetus for large-scale commercial development of
penicillin; by 1942 penicillin was being produced in large enough quantities to be used
to fight infection among wounded soldiers. British manufacturers had commenced
production using the only method available at that time: growing the Penicillium mould

(20) on the surface of a nutrient liquid. Once the mould colony had spread over the surface,
it was removed and penicillin was extracted from the liquid. Unfortunately, only a very
low yield was obtained in this way. Meanwhile, manufacturers in the United States
concentrated on improving production methods and eventually perfected the technique
of deep fermentation now used in the production of most antibiotics. This technique

(25) was based on the discovery that some species of Penicillium can be grown submerged in
liquid rather than on the liquid's surface; this method produces a higher yield of
penicillin.

Questions

18. Although Sir Alexander Fleming's discovery was made in 1928, -

(1) some time passed before researchers were able to identify exactly what killed
bacteria

(2) researchers were unable to isolate staphylococci for several years
(3) until recently, researchers were not sure how to grow a mould colony
(4) doctors refused to use penicillin until clinical trials had proved its effectiveness

)‫© כל הזכויות שמורות למרכז ארצי לבחינות ולהערכה (ע"ר‬

.‫ בלא אישור בכתב מהמרכז הארצי לבחינות ולהערכה‬- ‫ כולה או חלקים ממנה‬- ‫ או ללמדה‬,‫אין להעתיק או להפיץ בחינה זו או קטעים ממנה בכל צורה ובכל אמצעי‬