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All of the cells in a particular plant start out with the same
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Updated on: 25 Aug 2020, 06:13
Updated on: 25 Aug 2020, 06:13
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(00:45) wrong All of 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 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. 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 plant hormones are pleiotropic rather than specific; that is, each has more than one effect on the growth and development of plants. The five has so many simultaneous effects that they are not very useful in artificially controlling the growth of 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 produce ethylene.
The pleiotropy of the five well-studied plant hormones is somewhat analogous to that of certain hormones in animal. For example, hormones from the hypothalamus in the brain stimulate the anterior 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 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. Oligosaccharins are fragments of the cell wall released 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.
Unlike the oligosaccharins, the five well-known plant hormones are pleiotropic rather than specific; that is, each has more than one effect on the growth and development of plants. The five has so many simultaneous effects that they are not very useful in artificially controlling the growth of 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 produce ethylene.
The pleiotropy of the five well-studied plant hormones is somewhat analogous to that of certain hormones in animal. For example, hormones from the hypothalamus in the brain stimulate the anterior 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 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. Oligosaccharins are fragments of the cell wall released 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.
Supporting ideas
To answer this question, look for information that is provided in the passage. Lines 16–20 explain that each of the five plant hormones has more than one effect on the growth and development of plants; for this reason, they are not very useful in artificially controlling the growth of crops.
A Lines 20–25 describe in detail the multiple functions of the hormone auxin.
B Correct. The hormones have so many simultaneous effects on plants that they are not useful in controlling the growth of crops.
C The passage provides no evidence to support this reason.
D No information is given in the passage to support this reason.
E The hormones’ multiple effects on plant growth, not their specific effect at the cellular level, make them ineffective at artificially controlling crop growth.
The correct answer is B.
To answer this question, look for information that is provided in the passage. Lines 16–20 explain that each of the five plant hormones has more than one effect on the growth and development of plants; for this reason, they are not very useful in artificially controlling the growth of crops.
A Lines 20–25 describe in detail the multiple functions of the hormone auxin.
B Correct. The hormones have so many simultaneous effects on plants that they are not useful in controlling the growth of crops.
C The passage provides no evidence to support this reason.
D No information is given in the passage to support this reason.
E The hormones’ multiple effects on plant growth, not their specific effect at the cellular level, make them ineffective at artificially controlling crop growth.
The correct answer is B.
(A) it is not known exactly what functions the hormones perform
(B) each hormone has various effects on plants
(C) none of the hormones can function without the others
(D) each hormone has different effects on different kinds of plants
(E) each hormone works on only a small subset of a cell's genes at any particular time
2. The passage suggests that the place of hypothalamic hormones in the hormonal hierarchies of animals is similar to the place of which of the following in plants?
(A) plant cell walls
(B) the complement of genes in each plant cell
(C) a subset of a plant cell's gene complement
(D) the five major hormones
(E) the oligosaccharins
3. 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 particular plant cell
(E) to produce multiple effects on a particular subsystem of plant cells
4. The author mentions specific effects that auxin has on plant development in order to illustrate the
(A) point that some of the effects of plant hormones can be harmful
(B) way in which hormones are produced by plants
(C) hierarchical nature of the functioning of plant hormones
(D) differences among the best-known plant hormones
(E) concept of pleiotropy as it is exhibited by plant hormones
5. 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
6. The passage suggests that, unlike the pleiotropic hormones, oligosaccharins could be used effectively to
(A) trace the passage of chemicals through the walls of cells
(B) pinpoint functions of other plant hormones
(C) artificially control specific aspects of the development of crops
(D) alter the complement of genes in the cells of plants
(E) alter the effects of the five major hormones on plant development
7. The author discusses animal hormones primarily in order to
(A) introduce the idea of a hierarchy of hormones
(B) explain the effects that auxin has on plant cells
(C) contrast the functioning of plant hormones and animals hormones
(D) illustrate the way in which particular hormones affect animals
(E) explain the distinction between hormones and regulatory molecules
JOURNAL ARTICLE
Oligosaccharins
Peter Albersheim and Alan G. Darvill
Scientific American
Vol. 253, No. 3 (September 1985), pp. 58-65
Published by: Scientific American, a division of Nature America, Inc.
https://www.jstor.org/stable/24967788
Page Count: 8
Oligosaccharins
Peter Albersheim and Alan G. Darvill
Scientific American
Vol. 253, No. 3 (September 1985), pp. 58-65
Published by: Scientific American, a division of Nature America, Inc.
https://www.jstor.org/stable/24967788
Page Count: 8
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Re: All of the cells in a particular plant start out with the same
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13 Jul 2017, 20:47
13 Jul 2017, 20:47
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Expert Reply
anikacr7
Answer to question 3 and 5 please, with explanation.
Plus, for question 5, the last line says that there are indications hormones might work by activating enzymes that release oligosaccharins, so why is d not the answer for 5
Plus, for question 5, the last line says that there are indications hormones might work by activating enzymes that release oligosaccharins, so why is d not the answer for 5
Quote:
3. 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 particular plant cell
(e) to produce multiple effects on a particular subsystem of plant cells
The passage tells us that "a complex system of chemical messengers that in plants include hormones and other regulatory molecules" allows cells to "differentiate and form structures as different as roots, stems, leaves, and fruits." Furthermore, the passage tells us that the five well-known hormones, which are "pleiotropic" ("P's") because they have multiple effects, might function by activating certain enzymes that in turn release regulatory molecules called oligosaccharins ("O's"), which, because they are not "P's", have only one specific effect on the growth and development of plants.(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 particular plant cell
(e) to produce multiple effects on a particular subsystem of plant cells
In other words, the five "P's" activate enzymes which in turn release "O's", which have a single, specific effect on the growth and development of the plant (for example, forming roots, stems, leaves, or fruits). Thus, the passage suggests that the "O's" could be directly responsible for causing a plant cell to become part of a plant's root system. Thus, choice (A) is the best answer.
Quote:
5. 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
(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
As explained above, the "O's" have one specific effect on the growth and development of plants. How is this possible, when "all of the cells in a particular plant start out with the same complement of genes"? It's because "only a small subset of the genes in a particular kind of cell are expressed, or turned on, at a given time." Thus, it makes sense that the "O's" could function by "influencing the development of a plant's cells by controlling the expression of the cells' genes", as described in choice (E).
Quote:
(d) producing the hormones that cause plant cells to differentiate to perform different functions
(D) cannot be the answer because we are not told that the "O's" produce hormones. Rather, as described above, the "P" hormones activate enzymes that release "O" regulatory molecules, which in turn cause plant cells to differentiate and perform different functions.I hope that helps!
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Re: All of the cells in a particular plant start out with the same
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28 Aug 2014, 05:42
28 Aug 2014, 05:42
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10 mins.
1. according to the passage, the five well-known plant hormones are not useful in controlling the growth of crops because
(a) it is not known exactly what functions the hormones perform
(b) each hormone has various effects on plants
>> unlike the oligosaccharins, the five well-known plant hormones are pleiotropic rather than specific,
(c) none of the hormones can function without the others
(d) each hormone has different effects on different kinds of plants
(e) each hormone works on only a small subset of a cell's genes at any particular time
2. the passage suggests that the place of hypothalamic hormones in the hormonal hierarchies of animals is similar to the place of which of the following in plants?
(a) plant cell walls
(b) the complement of genes in each plant cell
(c) a subset of a plant cell's gene complement
(d) the five major hormones
>> Animal hormones example is presented to present the idea of hormone hierarchy in plants.
(e) the oligosaccharins
3. 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
>> unlike the oligosaccharins, the five well-known plant hormones are pleiotropic rather than specific,
(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 particular plant cell
(e) to produce multiple effects on a particular subsystem of plant cells
4. the author mentions specific effects that auxin has on plant development in order to illustrate the
(a) point that some of the effects of plant hormones can be harmful
(b) way in which hormones are produced by plants
(c) hierarchical nature of the functioning of plant hormones
(d) differences among the best-known plant hormones
(e) concept of pleiotropy as it is exhibited by plant hormones
>>the five well-known plant hormones are pleiotropic rather than specific.Since auxin has multiple effects.
5. 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
>> unlike the oligosaccharins, the five well-known plant hormones are pleiotropic rather than specific,
6. the passage suggests that, unlike the pleiotropic hormones, oligosaccharins could be used effectively to
(a) trace the passage of chemicals through the walls of cells
(b) pinpoint functions of other plant hormones
(c) artificially control specific aspects of the development of crops
>> Unlike P, O can influence specific property.
(d) alter the complement of genes in the cells of plants
(e) alter the effects of the five major hormones on plant development
7. the author discusses animal hormones primarily in order to
(a) introduce the idea of a hierarchy of hormones
>>the pleiotropy of the five well-studied plant <b>(25)</b> hormones is somewhat analogous to that of certain hormones in animal.
(b) explain the effects that auxin has on plant cells
(c) contrast the functioning of plant hormones and animals hormones
(d) illustrate the way in which particular hormones affect animals
(e) explain the distinction between hormones and regulatory molecules
1. according to the passage, the five well-known plant hormones are not useful in controlling the growth of crops because
(a) it is not known exactly what functions the hormones perform
(b) each hormone has various effects on plants
>> unlike the oligosaccharins, the five well-known plant hormones are pleiotropic rather than specific,
(c) none of the hormones can function without the others
(d) each hormone has different effects on different kinds of plants
(e) each hormone works on only a small subset of a cell's genes at any particular time
2. the passage suggests that the place of hypothalamic hormones in the hormonal hierarchies of animals is similar to the place of which of the following in plants?
(a) plant cell walls
(b) the complement of genes in each plant cell
(c) a subset of a plant cell's gene complement
(d) the five major hormones
>> Animal hormones example is presented to present the idea of hormone hierarchy in plants.
(e) the oligosaccharins
3. 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
>> unlike the oligosaccharins, the five well-known plant hormones are pleiotropic rather than specific,
(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 particular plant cell
(e) to produce multiple effects on a particular subsystem of plant cells
4. the author mentions specific effects that auxin has on plant development in order to illustrate the
(a) point that some of the effects of plant hormones can be harmful
(b) way in which hormones are produced by plants
(c) hierarchical nature of the functioning of plant hormones
(d) differences among the best-known plant hormones
(e) concept of pleiotropy as it is exhibited by plant hormones
>>the five well-known plant hormones are pleiotropic rather than specific.Since auxin has multiple effects.
5. 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
>> unlike the oligosaccharins, the five well-known plant hormones are pleiotropic rather than specific,
6. the passage suggests that, unlike the pleiotropic hormones, oligosaccharins could be used effectively to
(a) trace the passage of chemicals through the walls of cells
(b) pinpoint functions of other plant hormones
(c) artificially control specific aspects of the development of crops
>> Unlike P, O can influence specific property.
(d) alter the complement of genes in the cells of plants
(e) alter the effects of the five major hormones on plant development
7. the author discusses animal hormones primarily in order to
(a) introduce the idea of a hierarchy of hormones
>>the pleiotropy of the five well-studied plant <b>(25)</b> hormones is somewhat analogous to that of certain hormones in animal.
(b) explain the effects that auxin has on plant cells
(c) contrast the functioning of plant hormones and animals hormones
(d) illustrate the way in which particular hormones affect animals
(e) explain the distinction between hormones and regulatory molecules
