Round Four of our Deep Dive into MCAT Discrete Questions

Session 49

This is our 4th week of diving into a grab bag of discrete MCAT questions from various topic areas. Follow along and have a listen! Don't forget to subscribe.

[01:33] Metabolism Question

Question: Which of the following molecules would be expected to have the lowest tissue concentrations in active skeletal muscle deprived of O2.

  • (A) Glyceraldehyde 3-Phosphate
  • (B) Lactate
  • (C) Citrate
  • (D) Pyruvate

Bryan's Insights:

What's given is an active skeletal muscle but in the absence of O2 so we're talking about anaerobic, the kind of quick, explosive muscle movement rather than a sustained, marathon kind of muscle movement. Then they're looking for that which is not there, having the lowest tissue concentration.

If you recognize answer choices A, B, and D, they all have something in common. They're all parts of glycolysis. Glyceraldehyde 3-Phosphate is in the middle of the chain, Pyruvate is in the final step, and then Pyruvate is fermented into Lactate. These are all anaerobic and all part of glycolysis. Hence, the right answer is (C) Citrate because it's part of aerobic respiration (the Krebs Cycle or the Citric Acid Cycle).

[03:09] General Chemistry

Question #29: Which of the following factors would be most likely to cause acetic acid to completely dissociate in aqueous solution?

  • (A) Higher temperatures which increase the PKA of the acid
  • (B) Enzymes that catalyze the forward reaction
  • (C) Continuous addition of acetic acid to the solution
  • (D) Continuous removal of protons from the solution

Bryan's Insights:

You want to walk into the MCAT recognizing some of your classic weak acids and weak bases. Acetic acid is a classic weak acid which is literally, vinegar, which we take on a regular basis. The question wanted to completely dissociate but it's a weak acid so it doesn't really dissociate very much. We need to drive the process of dissociation forward and rip those protons off the acetic acid.

Think about the fact that if you want to drive a reaction forward to completion, one way to do that is to remove the products. If acetic acid breaks apart into acetate and proton, remove the proton. By Le Chatelier's principle, that will cause the reaction to continue moving forward. So answer choice (D) could theoretically get you to complete dissociation.

[04:50] Amino Acid Question

Question #47: Assuming all other conditions are equal, which of the following amino acids is expected to have the most positive charge of physiological pH?

  • (A) ARG
  • (B) MET
  • (C) ASN
  • (D) ASP

Bryan's Insights:

You would be expected to walk in knowing that ARG, which is the three-letter abbreviation for arginine, is a positive charge at physiological pH. MET is Methionine and ASN is Asparagine, and they're both neutral amino acids. They have a sulfur-containing group and an amide group but they're neutral at physiological pH. ASP, Aspartic acid or Aspartate, is a negative charge at physiological pH.

[07:24] Sociology Question

Question #59: In which of the following societies would anomie most likely be observed?

  • (A) A high school with a science and technology focus in which students who graduate are far more likely than average high school students to believe that arts funding is a waste of public money.
  • (B) A college of campus on which students are required to make such extensive use of technology that the level of normal face-to-face interaction drops precipitously below the norm at other college campuses.
  • (C) A large corporate campus for a multinational food additive company in which upper management actively promotes certain political views and candidates.
  • (D) A committee of military generals with high group cohesiveness that over-estimates its own ability to make military planning decisions and is unwilling to consider descent.

Bryan's Insights:

It's a classic sociology concept and any one of these can represent anomie although one answer choice should definitely standout to the well-prepared MCAT student as representing a different concept.

Answer choice (D) where a group of people with high cohesiveness, unwilling to consider outside views is a classic example of groupthink. Even if you didn't know what anomie is but you know what groupthink is then you can cross this answer choice out.

Bryan explains there's this incorrect perception of you can always get it down to two and you get the wrong one, which is this dismissal process of elimination.

Anomie is a situation in which society begins to break down because the normal interactions and values of a society have started to fall apart. It is primarily characterized by alienation and isolation. When people are feeling isolated from each other, they're feeling alienated from their larger society. In this case, answer choice (B) are college students who are extensively using technology that normal face-to-face interaction drops precipitously. So by not having that direct contact with their peers, this is a society that could be expressing this idea of anomie.

I personally think this is where we are going as a society right now with all our phones. Bryan adds that everyday there's a study that says the use of social media and phones makes you unhappy and is bad for you. This reminds of an article I found online featuring a newspaper article from the late 1800s and they were saying how society was going to end and that things were changing and it wasn't good, all because of kaleidoscopes where everybody in town had their face glued into their kaleidoscopes so history is just repeating itself over and over again.

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