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The complex life cycle of the Plasmodium protozoan, the causative agen

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The complex life cycle of the Plasmodium protozoan, the causative agen  [#permalink]

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New post Updated on: 18 May 2019, 21:21
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New Project RC Butler 2019 - Practice 2 RC Passages Everyday
Passage # 8 New, Date : 04-FEB-2019
This post is a part of New Project RC Butler 2019. Click here for Details


The complex life cycle of the Plasmodium protozoan, the causative agent of malaria, has contributed to the difficulty of devising effective public health measures to combat the disease. It took scientists centuries to deconstruct the basic relationship between protozoan, mosquito vector, and human host. Modern physiologists and epidemiologists are still working out the intricacies of malarial infection.

The disease is transmitted by the bite of a female Anopheles mosquito infected with the Plasmodium parasite. Only Anopheles mosquitoes are capable of transmitting the disease, and only females take blood meals from humans. To become infected with Plasmodium, the female mosquito takes a blood meal from a human carrying the parasite in his or her blood. Once ingested, the parasite matures in the mosquito’s gut for approximately a week, after which it migrates to the insect’s salivary glands. By mixing with the mosquito’s saliva, the parasite facilitates its transmission to a human host when the mosquito bites that human.

Once in a human’s bloodstream, the parasite travels to the human’s liver. At this initial stage, the Plasmodium parasite is called a sporozoite. Within the liver, the sporozoite can form 30,000 to 40,000 daughter cells, called merozoites, which are released into the host’s bloodstream at a later date, sometimes within a week of the initial infection and sometimes as much as several months later. The merozoites seek out and attach themselves to red blood cells, in which they incubate 8 to 24 daughter cells over the next two days. When the daughter cells are mature, the red blood cell ruptures and the new parasites are released into the bloodstream to seek out red blood cells of their own.

Some of the new merozoites become male and female gametocytes; if these gametocytes are ingested by a mosquito feeding on the host’s blood, they will fertilize in the mosquito’s gut to produce new sporozoites, and the cycle will continue. The symptoms that we associate with malaria—a high, recurring fever; joint pain; a swollen spleen are caused by toxins released from the red blood cells ruptured by merozoites. The human spleen can destroy these infected blood cells, but the Plasmodium parasite counters this effect by increasing the stickiness of proteins on the blood cells’ surfaces so that the cells stick to the walls of blood vessels. If the sticky surface proteins affect a particularly large number of cells, the malaria can transform into a hemorrhagic fever, the most deadly form of malaria.

A further complicating factor in the natural history of malaria is the many variants of the Plasmodium protozoan. Scientists now recognize that malaria is caused by at least six different species: P. falciparum, P. vivax, P. ovale, P. malariae, P. knowesli, and P. semiovale. Of these species, P. falciparum accounts for the majority of infections and approximately 90 percent of malarial deaths in the world.

1. The passage is primarily concerned with which of the following?

A. Describing the life cycle of the Plasmodium protozoan as it relates to the disease malaria
B. Comparing and contrasting the life cycles of the six variants of the Plasmodium protozoan known to cause malaria
C. Addressing the public health implications of the life cycle of the Plasmodium parasite
D. Providing information on how a person can avoid infection with malaria
E. Describing the life cycle of the Anopheles mosquito as it relates to the transmission of the Plasmodium protozoan to humans


2 . Which of the following most accurately states the role of the first paragraph in relation to the passage as a whole?

A. It summarizes two theories, the relative merits of which are debated in the passage.
B. It puts forth an argument that the rest of the passage is devoted to refuting.
C. It introduces a new concept that the rest of the passage expands upon.
D. It frames the background and relevance of the material to follow.
E. It outlines the major themes of each of the four paragraphs to follow.


3. If a mosquito were to bite a person, and that person were later to develop malaria and die of the disease, it is most likely that the person was infected with which of the following?

A. Anopheles gambiae
B. Anopheles semiovale
C. Plasmodium malariae
D. Plasmodium vivax
E. Plasmodium falciparum


4. The relationship of a merozoite to a sporozoite is most like which of the following?

A. A mother to a daughter
B. A brother to a sister
C. One of several subsidiaries spun off from a large corporation
D. A computer program to a computer
E. Orange juice to an orange tree


5. Based on the information given in the passage, which of the following would be most effective in preventing a person infected with malaria from developing a hemorrhagic fever?

A. Surgical removal of the spleen
B. A medicine that prevents changes to the surface proteins of red blood cells
C. An effective vaccine against malaria
D. A potent pesticide that reliably kills the Anopheles mosquito without producing any negative consequences for the environment or for human health
E. A small infusion of a weaker variant of the Plasmodium protozoan that will then compete with the existing parasitic infection



Source: McGraw Hills GMAT
Difficulty Level: 600

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Originally posted by SajjadAhmad on 21 Feb 2017, 05:41.
Last edited by SajjadAhmad on 18 May 2019, 21:21, edited 4 times in total.
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Re: The complex life cycle of the Plasmodium protozoan, the causative agen  [#permalink]

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New post 07 Feb 2019, 06:29
2
Official Explanation


1. The passage is primarily concerned with which of the following?

Explanation

The first three paragraphs are all directly addressed to the life cycle of the Plasmodium protozoan, and the last two paragraphs discuss the implications of the parasite’s life cycle for malaria in humans. Answer C is partially accurate, but the passage is certainly more focused on describing the life cycle of Plasmodium than on describing its public health implications, so A is the better answer.

ANSWER: A


2. Which of the following most accurately states the role of the first paragraph in relation to the passage as a whole?

Explanation

The first paragraph mentions the background of the effort to understand the life cycle of the malaria parasite (“It took scientists centuries to deconstruct the basic relationship between protozoan, mosquito vector, and human host”), and it provides relevance to the following passage by linking the topic to human health (“has contributed to the difficulty of devising effective public health measures to combat the disease”).

ANSWER: D


3. If a mosquito were to bite a person, and that person were later to develop malaria and die of the disease, it is most likely that the person was infected with which of the following?

Explanation

The passage states, “Of these species, P. falciparum accounts for the majority of infections and approximately 90 percent of malarial deaths in the world.”

ANSWER: E


4. The relationship of a merozoite to a sporozoite is most like which of the following?

Explanation

The passage states, “Within the liver, the sporozoite can form 30,000 to 40,000 daughter cells, called merozoites, which are released into the host’s blood stream at a later date,” so the relationship should be that of descent from the latter to the former, and of many from one, which answer C captures. Answer A could be correct if the order were reversed.

ANSWER: C


5. Based on the information given in the passage, which of the following would be most effective in preventing a person infected with malaria from developing a hemorrhagic fever?

Explanation

The passage states, “If the sticky surface proteins affect a particularly large number of cells, the malaria can transform into a hemorrhagic fever, the most deadly form of malaria.” Answer C is incorrect because a vaccination would not help an already infected person.

ANSWER: B


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Re: The complex life cycle of the Plasmodium protozoan, the causative agen  [#permalink]

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New post 05 Feb 2019, 08:43
3
1. The passage is primarily concerned with which of the following?

A. Describing the life cycle of the Plasmodium protozoan as it relates to the disease malaria
Correct
B. Comparing and contrasting the life cycles of the six variants of the Plasmodium protozoan known to cause malaria
No compare and contrast
C. Addressing the public health implications of the life cycle of the Plasmodium parasite
Scope of passage is not about public health implications but about life cycle of PP
D. Providing information on how a person can avoid infection with malaria
Irrelevant
E. Describing the life cycle of the Anopheles mosquito as it relates to the transmission of the Plasmodium protozoan to humans
passage is not about AM but about PP

2 . Which of the following most accurately states the role of the first paragraph in relation to the passage as a whole?

A. It summarizes two theories, the relative merits of which are debated in the passage.
There are no 2 theories
B. It puts forth an argument that the rest of the passage is devoted to refuting.
NO refuting/contradiction happens in passage
C. It introduces a new concept that the rest of the passage expands upon.
NO new concept is introduced, malaria is a disease
D. It frames the background and relevance of the material to follow.
correct
E. It outlines the major themes of each of the four paragraphs to follow.
Mentions that the life cycle of PP is complex

3. If a mosquito were to bite a person, and that person were later to develop malaria and die of the disease, it is most likely that the person was infected with which of the following?

A. Anopheles gambiae
B. Anopheles semiovale
C. Plasmodium malariae
D. Plasmodium vivax
E. Plasmodium falciparum - Based on last para, PF causing 90% deaths

4. The relationship of a merozoite to a sporozoite is most like which of the following?

A. A mother to a daughter -actually inverse merozite is the daughter
B. A brother to a sister
C. One of several subsidiaries spun off from a large corporation - COrrect - Sporozite produces merozite
D. A computer program to a computer
E. Orange juice to an orange tree

5. Based on the information given in the passage, which of the following would be most effective in preventing a person infected with malaria from developing a hemorrhagic fever?

A. Surgical removal of the spleen
B. A medicine that prevents changes to the surface proteins of red blood cells - COrrect - Given in 4th para
C. An effective vaccine against malaria
D. A potent pesticide that reliably kills the Anopheles mosquito without producing any negative consequences for the environment or for human health
E. A small infusion of a weaker variant of the Plasmodium protozoan that will then compete with the existing parasitic infection
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Re: The complex life cycle of the Plasmodium protozoan, the causative agen   [#permalink] 05 Feb 2019, 08:43
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