RC - Identifying cause

[karthikpandian19]

Certain chemical messengers, such as neurotransmitters, are formed from dietary constituents, which serve as chemical precursors. Furthermore, studies have shown that one can change his or her consumption of these precursors in order to alter the release of their respective neurotransmitter products. Acetylcholine, the neurotransmitter that serves as a message carrier between nerves and muscle cells, is formed from choline, a common constituent in fish, liver, and eggs. It follows, therefore, that the consumption of these foods, or dietary supplements that carry the same components, will aid the body's production of this chemical messenger.

In 2007, Kingsley et al. published a study demonstrating that oral supplementation of choline increases plasma choline levels and therefore increases the efficiency by which the body creates acetylcholine. Kingsley concluded that, due to the increase in their bodies' production of acetylcholine, athletes who supplemented their diets with artificial sources of choline would exhibit enhanced performance in activities that require extensive muscle contraction. When acetylcholine binds to receptors on skeletal muscle fibers, it opens sodium channels in the cell membrane allowing sodium ions to enter the muscle cell and initiate a sequence of steps that produce muscle contraction. Kinglsey also suggested that, due to its involvement in the formation of acetylcholine, low choline levels would be a contributing factor to the development of muscle fatigue.

However, in 2009, further studies suggested that an increase in a person's consumption of choline has only a negligible impact on his or her exercise performance. The researchers in this more recent study point out that choline is not only a precursor of the production of acetylcholine, but also a critical component of many fat-containing compounds in the cell membrane. This membrane surrounds all body cells, and because its growth is inextricably linked to adequate choline supplies, membrane formation is an alternative to acetylcholine synthesis as a major function of choline. In these studies, increasing plasma choline levels exerted no effect on either brief, high-intensity cycling tests or more prolonged aerobic exercise tasks. This conclusion is supported by a study of marathon runners supplementing their diets with choline who saw no improvement in endurance or athletic performance when participating in strenuous exercise.

The passage does NOT suggest which of the following?


(A) The role dietary choline plays in athletic performance is still unclear.

(B) An increase in blood choline levels does not result in an increase in acetylcholine production.

(C) Chemical messengers, such as neurotransmitters, require dietary constituents that serve as chemical precursors.

(D) Dietary supplements serve as alternatives to fish, liver, and eggs as a source of choline.

(E) Muscle fatigue may be one result of low levels of choline consumption and acetylcholine production.

[Birottam Dutta]

B is the choice that is not supported by the passage.

Even through atheistic performance based on consumption of choline is still unclear, it is never doubted that increased consumption of choline results in increased acetylcholine production.

hence, B!

[karthikpandian19]

I thought the similar way as B was the answer. But the OA is C

This is a fairly general question that requires a good understanding of details throughout the entire passage. Each answer choice will be something the passage either directly states or indirectly suggests. The correct answer choice is the one that cannot be logically concluded from the information in the passage.

Choice C is correct. There are two key words to take note of here: "require" and "certain." The first sentence of the passage states: Certain chemical messengers, such as neurotransmitters, are formed from dietary constituents, which serve as chemical precursors. Just because certain chemical messengers are formed from dietary constituents does not mean that "chemical messengers, such as neurotransmitters, require dietary constituents." Many neurotransmitters may not require dietary constituents at all. Therefore, this answer choice is not actually suggested by the information in the passage.

Choice A is a summary of the arguments within the passage. One study concludes that consumption of dietary choline improves athletic performance; the other study concludes that consumption of dietary choline has a negligible impact on athletic performance. It is logical to conclude, therefore, that "the role dietary choline plays in athletic performance is still unclear."

Choice B is suggested by one of the studies referenced in the passage. The 2009 studies mentioned in the last paragraph state that membrane formation is an alternative to acetylcholine synthesis as a major function of choline. The conclusion here is that an increase in blood choline is used by the membrane, instead of for acetylcholine production.

Choice D is stated directly in the first paragraph. the consumption of these foods [fish liver and eggs], or dietary supplements that carry the same components, will aid the body's production of this chemical messenger. Therefore, choline can be consumed in the form of food or dietary supplements and have the same effect.

Choice E is a paraphrase of Kingsley's conclusion at the end of the second paragraph. He stated that low choline levels would be a contributing factor to the development of muscle fatigue. Therefore, the passage does suggest that "muscle fatigue may be one result of low levels of choline consumption" and choice E can be eliminated.

B is the choice that is not supported by the passage.

Even through atheistic performance based on consumption of choline is still unclear, it is never doubted that increased consumption of choline results in increased acetylcholine production.

hence, B!