要想在
PASSAGE 6
Fungi, of which there are over 100,000 species, including yeasts and other
single-celled organisms as well as the common molds and mushrooms, were
formerly classified as members of the plant kingdom. However, in reality they are
Line very different from plants and today they are placed in a separate group altogether.
(5) The principal reason for this is that none of them possesses chlorophyll, and since
they cannot synthesize their own carbohydrates, they obtain their supplies either
from the breakdown of dead organic matter or from other living organisms.
Furthermore the walls of fungal cells are not made of cellulose, as those of plants
are, but of another complex sugarlike polymer called chitin, the material from which
(10) the hard outer skeletons of shrimps, spiders, and insects are made. The difference
between the chemical composition of the cell walls of fungi and those of plants
is of enormous importance because it enables the tips of the growing hyphae, the
threadlike cells of the fungus, to secrete enzymes that break down the walls of plant
cells without having any effect on those of the fungus itself. It is these cellulose-
(15) destroying enzymes that enable fungi to attack anything made from wood, wood
pulp, cotton, flax, or other plant material.
The destructive power of fungi is impressive. They are a major cause of structural
damage to building timbers, a cause of disease in animals and humans, and one of
the greatest causes of agricultural losses. Entire crops can be wiped out by fungal
(20) attacks both before and after harvesting. Some fungi can grow at +50°C, while
others can grow at -5°C, so even food in cold storage may not be completely safe
from them. On the other hand, fungi bring about the decomposition of dead organic
matter, thus enriching the soil and returning carbon dioxide to the atmosphere. They
also enter into a number of mutually beneficial relationships with plants and other
(25) organisms. In addition, fungi are the source of many of the most potent antibiotics
used in clinical medicine, including penicillin.
11. What does paragraph 1 mainly discuss?
(A) Differences between simply and complex fungi
(B) Functions of chlorophyll in plants
(C) Functions of sugar in the walls of fungal cells
(D) Differences between fungi and plants
12. Which of the following is mentioned as a major change in how scientists approach the study of fungi?
(A) Fungi are no longer classified as plants.
(B) Some single-cell organisms are no longer classified as fungi.
(C) New methods of species identification have been introduced.
(D) Theories about the chemical composition of fungi have been revised.
13. The word "principal" in line 5 is closest in meaning to
(A) true
(B) main
(C) logical
(D) obvious
14. According to the passage, how do fungi obtain carbohydrates?
(A) They absorb carbohydrates from their own cell walls.
(B) They synthesize chlorophyll to produce carbohydrates.
(C) They produce carbohydrates by breaking down chitin.
(D) They acquire carbohydrates from other organic matter, both living and dead.
15. The passage mentions shrimps, spiders, and insects in line 10 because their skeletons
(A) can be destroyed by fungi
(B) have unusual chemical compositions
(C) contain a material found in the walls of fungal cells
(D) secrete the same enzymes as the walls of fungal cells do
16. Which of the following terms is defined in the passage?
(A) "chlorophyll" (line5)
(B) "polymer" (line9)
(C) "hyphae" (line12)
(D) "enzymes" (line13)
17. The word "those" in line 14 refers to
(A) tips
(B) hyphae
(C) enzymes
(D) walls
18. Fungi have all of the following characteristics EXCEPT:
(A) They grow hyphae.
(B) They secrete enzymes.
(C) They synthesize cellulose.
(D) They destroy crops.
19. The word "Entire" in line 19 is closest in meaning to
(A) certain
(B) whole
(C) mature
(D) diseased
20. The passage describes the negative effects of fungi on all of the following EXCEPT
(A) buildings
(B) animals
(C) food
(D) soil
21. The phrase "bring about" in line 22 is closest in meaning to
(A) cause
(B) join
(C) take
(D) include
22. The passage mentions "penicillin" in line 26 as an example of
(A) a medicine derived from plants
(B) a beneficial use of fungi
(C) a product of the relationship between plants and fungi
(D) a type of fungi that grows at extreme temperatures.