求解og404页130.132题

saintaa

看了几遍还是不能理清这篇文章最后一段的逻辑，所以130和132题不知道做。
LineAll the cells in a particular plant start out with
the same complement of genes. How then can
these cells differentiate and form structures as
different as roots, stems, leaves, and fruits? The
(5) answer is that only a small subset of the genes in a
particular kind of cell are expressed, or turned on,
at a given time. This is accomplished by a complex
system of chemical messengers that in plants
include hormones and other regulatory molecules.
(10) Five major hormones have been identified: auxin,
abscisic acid, cytokinin, ethylene, and gibberellin.
Studies of plants have now identified a new class of
regulatory molecules called oligosaccharins.
Unlike the oligosaccharins, the five well-known
(15) plant hormones are pleiotropic rather than specific;
that is, each has more than one effect on the
growth and development of plants. The five have
so many simultaneous effects that they are not
very useful in artificially controlling the growth of
(20) crops. Auxin, for instance, stimulates the rate of
cell elongation, causes shoots to grow up and roots
to grow down, and inhibits the growth of lateral
shoots. Auxin also causes the plant to develop a
vascular system, to form lateral roots, and to
(25) produce ethylene.
The pleiotropy of the five well-studied plant
hormones is somewhat analogous to that of certain
hormones in animals. For example, hormones from
the hypothalamus in the brain stimulate the anterior
(30) lobe of the pituitary gland to synthesize and release
many different hormones, one of which stimulates
the release of hormones from the adrenal cortex.
These hormones have specific effects on target
organs all over the body. One hormone stimulates
(35) the thyroid gland, for example, another the ovarian
follicle cells, and so forth. In other words, there is a
hierarchy of hormones.
Such a hierarchy may also exist in plants. Oligo-
saccharins are fragments of the cell wall released
(40) by enzymes: different enzymes release different
oligosaccharins. There are indications that pleiotropic
plant hormones may actually function by activating
the enzymes that release these other, more specific
chemical messengers from the cell wall.
130.The passage suggests that which of the following is a
function likely to be performed by an oligosaccharin?
(A)To stimulate a particular plant cell to become
part of a plant’s root system
(B)To stimulate the walls of a particular cell to
produce other oligosaccharins
(C)To activate enzymes that release specific
chemical messengers from plant cell walls
(D)To duplicate the gene complement in a particula
plant cell
(E)To produce multiple effects on a particular
subsystem of plant cells
132.According to the passage, which of the following best
describes a function performed by oligosaccharins?
(A)Regulating the daily functioning of a plant’s cells
(B)Interacting with one another to produce different
chemicals
(C)Releasing specific chemical messengers from a
plant’s cell walls
(D)Producing the hormones that cause plant cells
to differentiate to perform different functions
(E)Influencing the development of a plant’s cells by
controlling the expression of the cells’ genes

honoluluhono

130.A 132.E   OG不在手边，是这个答案吗？选项确实有点似是而非。

saintaa

是的呢 可以麻烦楼上的解释一下嘛 谢谢

honoluluhono

高中理科有生物印象的话应该不难理解这个背景，但没有也完全没关系，文章大概思路如下：
植物所有细胞都包含相同的基因，为什么细胞会分化成不同的部分？因为只有特定细胞里的特定一部分基因在特定的时间里能够表达出来，怎么表达的？拜这两种东西所赐：hormones and other regulatory molecules. (不懂专业术语可以忽略，知道是这两个单词就行了) 发现了5种主要的hormones：1.2.3.4.5和一组新的叫oligosaccharins的regulatory molecules。5种hormones作用是复合的，举例省略。而oligosaccharins作用比较单一，即一种oligosaccharins一个作用。
还发现，这5种hormones的复合作用性质在植物中和在动物中是一样的。举了个例说动物里的一种hormones可以刺激产生另一种hormones,再通过后者hormones产生某具体的效用。(这个举例比较关键，所以不省略)，换句话说，hormones是有层次的。
hormones的这种层次性在植物中也是存在的。开始举例。Oligo-saccharins由enzymes产生，不同的enzymes产生不同的Oligo-saccharins。有证据显示呢，有些植物是通过激活enzymes，再由enzymes刺激细胞壁释放类似Oligo-saccharins这样的specific chemical messenger作用的。

130. oligosaccharin是有特定作用的，而hormones是复合作用，选A对，虽然文章没有明确提到有这种刺激root system的oligosaccharin，但根据oligo-saccharin的性质或定义是可以推断出来的。B错，因为这是enzymes的作用，没有一种oligo-saccharin产生另一种oligo-saccharin的，hormones才有这种层次性。C错，activate enzymes的是某hormones不是oligosaccharin。D错，没提到。E错，说的是hormones。

132. A错没提到，B错，这个我犹豫了一下，oligo-saccharin受到enzymes的刺激而产生，算不算interact，后来想想不算，interact应该是两样东西都存在再interact，而oligo-saccharin和enzymes的产生由先后，且是一个产生了另一个，不是两个interact产生了第三样东西。C错，chemical messengers包括oligosaccharin。D错，oligo-saccharin与hormones的谁产生谁的关系原文中没提到，只说了他俩有复合作用和单一作用的区别。E对，oligo-saccharin有单一作用，所以能影响到植物细胞的基因表达，从而影响到植物生长。

saintaa

哇。楼主的逻辑很严实，太感谢咯 。懂了

elsachialee

132 的B 選項的意思應該是不同種類之間的oligosaccharins interact 吧，文章沒有提到