Why the MCAT Bio / Biochem section is so critical and how to read a passage, Part II
Note: this post assumes familiarity with Part I, available here.
Welcome to the second installment of this series on reading MCAT passages more effectively. The whole point of the last entry was to arm you with the tools you need to completely understand the passage. Your passage map, which is a paragraph-by-paragraph breakdown of key relationships, hypotheses, and results, should completely replace the passage so you’ll theoretically never have to refer back to it again. In fact, that’s why I won’t include the passage in this post; our passage map is more than sufficient.
Here’s the thing, though: you’re going to be extremely slow at first, but isn’t that little bit of speed sacrifice worth it for the end game of complete mastery of any passage, no matter how abstruse or obscure? If you agree, read on.
Let’s start with a prototypical question and go through it gratuitously to the point of overkill. Remember this is slow.
This is an extremely common problem type: what conclusion can be drawn from the data? Let’s go back to our passage map (see previous post on how we did this) as a recap on what’s going on in the passage:
- Paragraph 1: Endometrial carcinomas (ECs) kill because they spread. Before we treat it, we need to understand it.
- Paragraph 2:
MSCs ↑ ⟼ Spreadability ↑ & Tumor growth ↑.
Cancer: MSCs ↑ ⟼ MSC marker = SUSD2 ↑ ⟼ Spreadability ↑ & Tumor growth ↑.
TGFß ↑ ⟼ SUSD2 ↓
- Paragraph 3:
- Paragraph 4:
Aging ↑ ⟼DNA damage↑ ⟼ Apoptosis ↑ OR Senescence ↑
Senescence ↑ ⟼ SMAD 2/3 ↑ ⟼ Proliferation / Apoptosis / Differentiation Regulation ↑
- Figure 1: SUSD ↓ ⟼ SMAD 2/3 ↓
- Paragraph 5 + Figure 2:
Expt. 1 — TGFß ↑ ⟼ apoptosis ↑
Expt. 2 — SUSD ↓ ⟼ apoptosis ↑
For clarity, I’ll include Figure 2,
Here we see that when we activate the TGFß pathway, apoptosis occurs. Our paragraph 3 illustration is also exactly what happened in the experimental group of Expt. 1 in the second set of experiments (paragraph 5): recall how the researchers incubated one Ishikawa strain in TGFß (light gray) and we saw a statistically significant rise in apoptosis (since the figure 2 caption notes that sub G0-G1 = apoptotic cells).
Aren’t you glad you took the time to understand each word? See the tips in the last post. Had you not taken the time, you could’ve easily missed the critical bit of information embedded in literally the last line of the entire passage. I can’t tell you how many practice problems I missed because I failed to read the last line of the passage. Read every word — if you want a 515+, you need to read and understand every word.
The idea behind taking copious but concise notes (meaning using many mathematical- and logic-like symbols and arrows to denote relationships) is so you can quickly recall the key relationships you’re tasked with keeping track of without having to re-read the passage text.
OK, where were we? The question. OK, when tackling questions, always remember:
Tip 5: restate the question stem by distilling it down to its essence
This tip may sound fruity, but the MCAT loves to throw a wall of text as a question with the express intent to intimidate. Like we did in Part I for each paragraph, we need to drill down to the creamy, delicious core of each question stem. Why? It makes the next tip so much easier.
Tip 6: Concatenate your restated question stem with each answer choice. If, as a whole, the statement is logical, that’s your answer
What do I mean? Let’s use our question to illustrate this:
Restated, we can say: “based on Figure 2, the following conclusion is unfounded.” That’s what Tip 5 asks us to do.
Next, per Tip 6, we join together our restated question stem with each answer choice and evaluate this “Frankenstein sentence” for veracity. Here are the choices again.
The first Frankenstein sentence we will make uses choice A, where the restated component is in bold whereas the substituted answer choice is italicized:
“A. Based on Figure 2, the following conclusion is unfounded: loss of SUSD2 results in increased expression of CASP2, a protease that promotes apoptosis.”
We should now convert this into a form that matches our passage map so we can quickly verify if we should accept our Frankenstein sentence as valid or not. So, we can say:
An invalid conclusion from Figure 2 is that SUSD ↓ ⟼ CASP2 ↑ ⟼ apoptosis ↑
This should look familiar. Take a look at the Paragraph 5 + Figure 2 passage map:
- Paragraph 5 + Figure 2:
Expt. 1 — TGFß ↑ ⟼ apoptosis ↑
Expt. 2 — SUSD ↓ ⟼ apoptosis ↑
The last line, about Expt. 2, is ultra key. Notice how it is actually a partially collapsed form of the relationship we noted for our first Frankenstein sentence:
An invalid conclusion from Figure 2 is that SUSD ↓ ⟼ CASP2 ↑ ⟼ apoptosis ↑
But we already said that Expt. 2 — SUSD ↓ ⟼ apoptosis ↑, so this is an obvious contradiction. Answer choice A is a legitimate conclusion that can be drawn from Figure 2. Notice how we didn’t have to return to the passage at all. Note how we didn’t care that CASP2 wasn’t mentioned in the passage once. You actually don’t need to know a single thing about CASP2 to answer this question correctly. All we needed was a relationship equation to compare our Frankenstein answer to (remember how we noticed that USD ↓ ⟼ CASP2 ↑ ⟼ apoptosis ↑ is just an expanded form of SUSD ↓ ⟼ apoptosis ↑).
Let’s try answer B:
“B. Based on Figure 2, the following conclusion is unfounded: downregulation of galectin-1, a SUSD2 interaction partner, inhibits the invasiveness of prostate carcinomas.”
Let’s proceed in the same manner:
An invalid conclusion from Figure 2 is that Galectin-1 ↓ ⟼ SUSD ↓ ⟼ invasiveness ↓
Notice how “downregulation” and “inhibits” both get a down arrow (since Galectin was downregulated and invasiveness was inhibited). This is illustrative of just how powerful these methods are in quickly zeroing in on the right answer like a laser-guided ICBM. With mathematical notation, we no longer have to deal with the vagaries and obfuscation of language to figure out what’s being asked and what’s going on. We literally have zero time for that. Had we not made this relationship explicit, you would’ve had to wade through dense text over and over again, wasting time you don’t have. You might be wondering why I was able to conclude that Galectin-1 downregulation necessarily implies that SUSD2 gets a down arrow, but it’s actually a straightforward logical conclusion that can be drawn since Galectin and SUSD2 are interaction partners. So now we ask: is it unfounded to conclude that SUSD and Galectin-1 play a role in invasiveness? Absolutely not. In fact, our passage map reiterates that relationship several times from paragraph 2:
MSCs ↑ ⟼ Spreadability ↑ & Tumor growth ↑.
Cancer: MSCs ↑ ⟼ MSC marker = SUSD2 ↑ ⟼ Spreadability ↑ & Tumor growth ↑.
So we can also eliminate B. Onto C:
“C. Based on Figure 2, the following conclusion is unfounded: Addition of the TGFβ receptor inhibitor A83–01 is shown to block apoptosis in actively proliferating Ishikawa cells.”
What’s C actually saying? When we block the entire TGFß pathway (see our paragraph 3 illustration), tumorigenic endometrial adenocarcinoma (Ishikawa) cells tend not to enter apoptosis.
Take a step back. Our Frankenstein sentence distilled to the very core is now:
“C. Based on Figure 2, the following conclusion is unfounded: TGFβ ↓ ⟼ apoptosis ↓.
We know from the question stem that our focus in on paragraph 5 + figure 2, so all we need to do is consult our relationships. We noted that:
Expt. 1 — TGFß ↑ ⟼ apoptosis ↑
The beauty of these relationships is that they can be inverted or negated like logical connectives and mathematical relationships. In other words, if TGFß is upregulated, so is apoptosis. If we block TGFß, instead, we block apoptosis. Notice how the change is preserved across the leftward pointing arrow. Symbolically:
TGFß ↑ ⟼ apoptosis ↑, then -(TGFß ↑ ⟼ apoptosis ↑) = TGFß ↓ ⟼ apoptosis ↓
[I am saying that ↑ = -(↓) and ↓ = -(-↓).]
Recall how our Frankenstein C is
“C. Based on Figure 2, the following conclusion is unfounded: TGFβ ↓ ⟼ apoptosis ↓”
but we literally just showed that we can conclude that TGFß ↓ ⟼ apoptosis ↓, so our Frankenstein sentence is invalid, because the conclusion is very much founded.
We eliminated A, B, and C. By process of elimination, that only leaves D. Let’s use our strategy anyway for edification. Our Frankenstein sentence is:
“D. Based on Figure 2, the following conclusion is unfounded: TGFβ ↑ and SMAD 4 ↓⟼ apoptosis ↑”
Where we distilled “after incubation with TGFβ, Ishikawa cells lacking functional SMAD 4 become apoptotic” into a mathematical relationship. The beauty of the MCAT is that often, you have more than one piece of evidence in the answer’s favor as a sort of insurance policy by the test writers to give people several opportunities to select the correct answer. Our first piece of evidence in favor of D was via process of elimination. Our next piece of evidence is from our illustration of paragraph 3. Let’s translate it into our mathematical form:
TGFß signal pathway: Ligand binding ↑ ⟼ SMAD 2/3 phosphorylation ↑ ⟼ SMAD 2/3 hooking up with SMAD 4 ↑ ⟼ Proliferation / Apoptosis / Differentiation Regulation ↑
Now, does this gel with our Frankenstein D? Nope! Our answer choice states that a nonfunctional SMAD 4 could somehow still regulate apoptosis. But without a SMAD 4 to link up with our phosphorylated intracellular signals SMADs 2 and 3, the transcription factor complex will not translocate to the nucleus. Recall that transcription factors are like aviation marshals who you see on the ground at airports waving torches to guide taxiing airplanes, but are actually proteins that gather at promoter regions near genes of interest beckoning an RNA polymerase to synthesize a transcript.
And that’s how you want to tackle each and every question you encounter on the MCAT. I love algorithms because they guarantee a solution eventually. Obviously not every word will be tested, and there will be passages where you barely need to read the passage to perfectly answer the questions. Cool. Use the strategy every time for the seven hours you’re in the exam. In order to get the most out of this strategy, you have to apply it methodically and deliberately each and every painful time. Once you do that, say goodbye to mediocrity forever, and welcome to the upper echelons of achievement.
Stay tuned for the next installment, where I will go over even more questions pertaining to this passage. I don’t think you’re quite convinced that my methods work every time, and I need to change that.
By the way, these tips are adapted from the experts at Altius Test Prep, North America’s fastest growing test prep company with industry-defying results. If you’d like to learn more, please don’t hesitate to reach out to me at: arjan (DOT) premed (AT) gmail (DOT) com, where the parentheticals denote which symbol to substitute in, e.g. (AT) = “@”.
Previous post: Part I
Next post: Part III
