The dosage for any prescribed medicine is the result of compromise.

Question

The dosage for any prescribed medicine is the result of compromise. All drugs are potentially poisonous, suggesting that the least possible amount should be administered. On the other hand, drugs become diluted in the blood and large amounts are degraded, taken up by healthy tissue, or excreted without reaching the site of disease. Physicians must balance these opposing considerations in determining effective doses.

To reduce the risks and inefficiency associated with such determinations, ways are now being developed to deliver the needed dose of medicine to diseased tissues while bypassing healthy ones. One promising approach is the loading of medication into liposomes—microscopic sacs (vesicles) made of the same phospholipids that constitute cell membranes.

A British scientist, Alec D. Bangham, inadvertently produced the first liposomes in 1961 while experimenting with the effect of phospholipids on blood clotting. Because liposomes are made of the same substance as cell membranes, researchers assumed that the liposomes would be nontoxic and would escape recognition and removal by the body’s immune system; the vesicles might therefore have the opportunity to interact with targeted cells in ways that would cause the vesicles to release their cargoes.

If these assumptions were correct and if liposomes could, as expected, be readily loaded with drugs, all that would be needed to complete this ideal drug-delivery system would be the attachment of tissue-specific molecules to the outside of the drug-laden vesicles. The liposomes, which were also expected to protect their loads from dilution or degradation, would be attached to the target tissues by the tissue-specific molecules.

Research has shown that liposomes can be loaded with drugs, are nontoxic, protect their loads, and can deliver concentrated doses of medication. Unfortunately, liposomes are for the most part unable to leave the circulatory system and hence are unlikely to reach most cell types. Unencapsulated, or free, drugs typically diffuse through capillary walls into tissues, but liposomes are too large to pass through the walls of most capillaries. In addition, the body’s immune system does recognize the liposomes and attempts to remove them from circulation.

1. The second paragraph serves primarily to

A. explain the difficulties encountered in prescribing effective drug doses
B. introduce liposomes as a possible solution to a problem faced by physicians
C. discuss the reasons for the effectiveness of liposomes in delivering drugs
D. define the term "liposome"
E. summarize early researchers’ findings about liposomes

2. The passage suggests that liposomes could be made more useful as a drug-delivery system if a way were discovered to

A. make liposomes smaller
B. make liposome walls thicker
C. make liposomes of different shapes
D. enable each liposome to carry a greater amount of medication
E. enable liposomes to travel through the entire circulatory system

3. The passage states that there is a risk associated with administering drugs because

A. some patient reactions to drugs are unpredictable
B. some drugs are difficult to administer properly
C. drugs must sometimes be administered in concentrated doses
D. all drugs are potentially poisonous
E. all tissues are at times sensitive to certain drugs

4. According to the passage, researchers hypothesized that liposomes would release their cargoes during interactions with

A. capillary walls
B. blood clots
C. other liposomes
D. targeted cells
E. the body’s immune system

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Show Answer Question #1

Official Answer

B

Show Answer Question #2

Official Answer

A

Show Answer Question #3

Official Answer

D

Show Answer Question #4

Official Answer

D

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Riya1475828 · Answer

Why is 2 not E?

GMATNinja   MartyMurray   GMATNinja Two

Sajjad1994 · Answer

Explanation

2. The passage suggests that liposomes could be made more useful as a drug-delivery system if a way were discovered to

Explanation

A.   This option aligns with the challenges discussed in the passage regarding liposomes being too large to pass through the walls of most capillaries. If liposomes were made smaller, they might be able to traverse these barriers more effectively, allowing them to reach a wider range of cell types. Therefore, making liposomes smaller could potentially enhance their usefulness as a drug-delivery system, addressing the limitation mentioned in the passage.

B.  This option is not supported by the passage. Thicker liposome walls would likely not address the issue of liposomes being unable to leave the circulatory system or pass through capillary walls. Therefore, this option does not address the main challenge discussed in the passage.

C.  While changing the shape of liposomes could potentially have some effects on their behavior in the body, the passage does not suggest that altering their shape would specifically address the challenges discussed, such as their inability to leave the circulatory system or pass through capillary walls. Therefore, this option is not directly relevant to the main issue mentioned in the passage.

D.  This option could potentially enhance the drug-delivery capabilities of liposomes by increasing the amount of medication they can carry. However, it does not address the issue of liposomes being unable to leave the circulatory system or pass through capillary walls, which are the primary challenges discussed in the passage.

E.  This option is not directly relevant to the main challenge discussed in the passage. The issue with liposomes is not their inability to travel through the entire circulatory system but rather their inability to leave the circulatory system and reach most cell types. Therefore, this option does not address the primary challenge mentioned in the passage.

Answer: A

GMATNinja · Answer

Question 2 
 
Question 2 asks how liposomes could be made more useful. To answer this question, it's important to understand why liposomes AREN'T useful in their current state.

The author mentions two problems with liposomes at the end of the last paragraph. The first problem is that liposomes are stuck in the circulatory system and so  can't reach "most cell types" -- the cell types that exist  outside  of the circulatory system. Why are they stuck in the circulatory system? They can't "pass through the walls of most capillaries" like other drugs can because they are too big. The second issue with liposomes is that the body's immune system tries to remove them.

Which answer choice addresses one of these shortcomings? Starting with (E):

Liposomes can ALREADY travel throughout the entire circulatory system. It's just that they can't escape  beyond  the circulatory system to get to other organs. Because (E) is already true, it doesn't identify something that would make liposomes more effective than they already are. Eliminate (E).

Here's (A):

The first problem with liposomes is that they are too big to pass through the walls of most capillaries, which means that they are stuck in the ciculatory system. If liposomes were smaller, that would resolve this issue.

(A) identifies a way to make liposomes more useful, so (A) is the correct answer to question 2.

I hope that helps!

wasario · Answer

My personal explanations for the answers (note: all of these questions fall under the types of questions where you have to go looking in the passage for the exact answer):

1. The first paragraph sets the premise of how drug administration is tricky due to the difficulty in finding not too much but not too little of the drug to administer. The second paragraph builds on top of this by saying "One promising approach is the loading of medication into liposomes...", providing a potential solution to the problem stated in the first paragraph. Answer choice  B  matches this.

2. In the final paragraph, the passage states "Unencapsulated, or free, drugs typically diffuse through capillary walls into tissues, but liposomes are too large to pass through the walls of most capillaries". In other words, if the liposomes were smaller, they would be able to pass through the capillaries and diffuse the drugs into the tissues.  A  matches this best. (Note: it seems a lot of people picked E, which is a trap answer. E sounds right at first, but the problem with this answer choice is that it's too extreme by saying "the entire circulatory system". The passage does not mention anywhere that liposomes need access to the whole body's system to function)

3. In the first paragraph, it states "All drugs are potentially poisonous, suggesting that the least possible amount should be administered". Answer choice  D  is correct. Usually, answers with extreme words like "all" or "never" are not correct, but in this case this extreme declaration is mentioned explicitly in the passage, so it's an exception to this rule.

4. In the third paragraph, it states "the vesicles might therefore have the opportunity to interact with targeted cells in ways that would cause the vesicles to release their cargoes". Answer choice  D  is correct.

Jan17 · Answer

Its because of this part "  Unencapsulated, or free, drugs typically diffuse through capillary walls into tissues, but liposomes are too large to pass through the walls of most capillaries."

The dosage for any prescribed medicine is the result of compromise.

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The dosage for any prescribed medicine is the result of compromise.

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