AAMC 10 Bio (ulcers)

[tmh]

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Hi guys,

In Passage VI of the Bio section of AAMC 7, item 130 asks "Which of the following statements explains most plausibly why host antibodies are ineffective against H. pylori?"

The answer is A) Antibody proteins may be denatured in the harsh environment of the stomach.
This was my gut reaction, but I thought about it again and it seemed to imply that the antibodies would enter via the digestive tract. I thought they would never have been exposed to the lumen of the stomach.

I put D) Antibodies are not secreted from host tissues into extracellular spaces. I know that antibodies can be found in extracellular spaces (eg. the blood), but thought maybe this could have been true.

Why was I wrong?

Thanks.

 

[MT Headed]

The answer is A) Antibody proteins may be denatured in the harsh environment of the stomach.
This was my gut reaction,

This must be from the paper version of the test (oh why?) because my CBT passage #s and problem #s are totally different. Anyway, this is one of those MCAT logic / reading comprehension problems masquerading as a biology problem.

Answer D says something that you yourself know is patently false. Antibodies are secreted from tissues (plasma cells of the blood connective tissue) into extracellular spaces. You fell into the logical trap of thinking that the stomach lumen is an extracellular space, and antibodies are not secreted into the stomach, therefore antibodies are not secreted into extracellular spaces. That is a logical error.

Sure if answer D) said something like "Antibodies are not secreted from host tissues into some extracellular spaces" you'd have a difficult time picking the best answer between A) and D).

 

[tmh]

Oh sorry, this is AAMC 7. I took the CBT version.

I see why D is definitely wrong now, but I still don't understand why the antibodies would ever come in contact with the gastric acid.

Thanks a lot.


...and I'm glad you caught my pun.