MCAT Chemistry Questions: Study Tips from MD Experts

What is Tested on the MCAT Chemistry and Physics section?

The MCAT Chemistry and Physics section of the test, like the MCAT Biology section, examines your knowledge and application of a broad range of scientific subjects, formulas and equations.

"The most challenging aspect for me was definitely the application of knowledge. While I was confident in my understanding of the topics, applying the knowledge to complex scenarios presented in the questions was challenging. The questions often require applying memorized facts and concepts to analyze novel scenarios and solve problems, not just rote recall." – Dr. Cathleen Kuo, MD, SUNY Buffalo

So, what academic disciplines are covered in the Chemical and Physical Foundations of Biological Systems section—sometimes referred to simply as the “chemistry and physics” section—of the MCAT? Questions included in this section breakdown as follows:

The concepts are combined with scientific inquiry and reasoning skills. The CPBS section incorporates concepts taught in your introductory level chemistry courses and relates these concepts back to biology and physiology. 

The chemistry and physics section covers the following foundational concepts:

1. Complex living organisms transport materials, sense their environment, process signals, and respond to changes using processes understood in terms of physical principles
2. The principles that govern chemical interactions and reactions form the basis for a broader understanding of the molecular dynamics of living systems

The AAMC’s overview of what’s on the MCAT offers a detailed list of the subtopics included within each foundational concept of the Chemical and Physical Foundations of Biological Systems section of the MCAT. The CPBS section’s main subtopics include:

Sample MCAT Chemistry and Physics Questions

Start your prep with some MCAT chemistry practice passages:

Passage

The heme enzyme indoleamine 2,3 dioxygenase (IDO) catalyzes Reaction 1, the first and rate-determining step of L-tryptophan (Compound 1) metabolism and is an important enzyme of the human immune system.

The IDO-catalyzed oxidation of Compound 1 by H2O2 does not occur. However, researchers have recently discovered that IDO-catalyzed oxidation of indole (Compound 3) by H2O2 (Reaction 2) does occur.

Under the conditions employed, the number of catalytic turnovers appeared to stop at roughly 100, on average. A plot of the concentration of Compound 3 that was oxidized versus the concentration of H2O2 employed, at two different initial concentrations of IDO, gave the results shown in Figure 1.

Aerobic oxidation of Compound 3 in the presence of 18O-labeled H218O2 resulted in the formation of 18O-labeled oxidation products (Table 1).

The formation of Compound 6 does not appear to be the result of a sequential oxidation process. Isotopically labeled Compound 4 does not exchange 18O for 16O in water over 3 hours, but Compound 6 completely loses its 18O label in unlabeled water over the same time period.

Adapted from: Kuo HH, Mauk AG. Indole peroxygenase activity of indoleamine 2,3-dioxygenase. Proceedings of the National Academy of Sciences of the United States of America. 2012;109(35):13966–71.

Sample Questions and Answers

Looking for more on what the chemistry and physics section looks like? Check this out:

6. The following kinetic parameters were obtained for the IDO-catalyzed oxidation of Compound 3 by H2O2 in the presence of L-Trp.

Based on this data, what effect does L-Trp have on the reaction?

A) L-Trp oxidizes Compound 3 directly.

B) L-Trp is oxidized instead of Compound 3.

C) L-Trp does not interact with the enzyme.

D) L-Trp inhibits the enzyme.

7. Four different solutions of a single amino acid were titrated, and the pK values of the solute were determined.

Which solution contains an amino acid that would be most likely to stabilize an anionic substrate in an enzyme pocket at physiological pH?

A) Solution 1

B) Solution 2

C) Solution 3

D) Solution 4

Tips for the Chemistry and Physics Section of the MCAT

Tip #1: Prep for Chemistry and Physics Data and Experiments

The AAMC typically tests students with chemistry and physics experiments in the form of passage-based questions. This means that you cannot just practice vocabulary and memorize equations. You must be able to apply your knowledge to a scenario in a passage. Regular practice with passage-based questions will help develop this skill.

“Brushing up on my content knowledge through undergraduate courses (Organic Chemistry I and II) helped. Doing passage-based questions to then apply this knowledge in MCAT-form further reinforced this … Watching relevant videos helped to keep organic chemistry 'fun' while working on my knowledge base.” – Dr. Neel Mistry, MD, University of Ottawa Faculty of Medicine.

"I made a conscious effort to relate biology and chemistry concepts to real-life applications and examples. This not only enhanced my understanding but also kept me motivated to learn. I also incorporated variety into my study sessions by alternating between learning materials and practicing questions. This approach helped me stay focused and made the study process more enjoyable." – Dr. Cathleen Kuo, MD.

Take some time to learn how to read MCAT graphs, as well, since this section of the MCAT will make liberal use of them and you want to be ready to tackle them quickly.

Tip #2: Mimic Test Day Conditions and Brush Up on Your Math Skills

You won’t have access to a calculator on exam day, so as you prepare for the MCAT it’s important that you complete practice questions in conditions that will mimic those of the test day. This means that since you will not have a calculator during the MCAT, don’t practice with a calculator! Brush up on math skills involving exponents, scientific notation, and multiplication and division of complex numbers. You will not have a calculator, but you will have access to the MCAT periodic table of elements, so be sure you know how to use it.

“Just think about it like you're an athlete – you have to prepare under realistic conditions if you want to get the best performance.” – Rishi, former BeMo student and current student at Carver College of Medicine.

 “Identify which topics you feel strongest and those you feel weakest. Then I would devote time to [reviewing] weaker topics while continually studying the stronger topics using flash cards or questions.” – Dr. Monica Taneja, MD, University of Maryland School of Medicine.

Tip #3: Know Your Units and Equations

Knowing your standard SI units and how to perform unit conversions seems basic, but they are foundational to understanding the context of MCAT questions. When feeling the exam approaching, you can easily start to panic if the answer you get is not among the answer choices. However, a simple unit conversion or a switch to scientific notation may reveal the correct answer. Similarly, you will need to know many foundational MCAT physics equations.

Using flashcards other active learning techniques can help you practice using and converting equations.

"Creating detailed diagrams for each topic and an equation sheet with key formulas helped me visualize and recall information quickly. Explaining concepts to myself out loud also solidified my understanding ... I incorporated short breaks with activities like going for walks or listening to science podcasts. I also found physics-related documentaries and engaging YouTube channels that helped me learn in a more interactive way." – Dr. Cathleen Kuo, MD.

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Source: AAMC Sample Question Guide 

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