MCAT Biology Questions: Advice From MD Experts

What’s Tested on the MCAT Biology and Biochemistry Section 

Most students are intimidated by the expansive volume of information involved in reviewing for the MCAT, and the BBFLS section most of all. This part of the test incorporates concepts taught at university during introductory-level biology and chemistry courses, as well as first-semester biochemistry courses.

“Although biology is my favorite subject, the hardest part I found was making sense of the passages/experimental studies and their findings within the given time limit. I found the passages to be extremely dense at times but breaking it down into simple terms and focusing on the key results helped.” – Dr. Neel Mistry, MD, University of Ottawa Faculty of Medicine.

The MCAT biology and biochemistry section covers the following foundational concepts: 

Foundational Concept 1

• 55% of questions
• Biomolecules have unique properties that determine how they contribute to the structure and function of cells and how they participate in the processes necessary to maintain life.

Foundational Concept 2

• 20% of questions
• Highly-organized assemblies of molecules, cells, and organs interact to carry out the functions of living organisms

Foundational Concept 3

• 25% of questions
• Complex systems of tissues and organs sense the internal and external environments of multicellular organisms, and through integrated functioning, maintain a stable internal environment within an ever-changing external environment.

For a detailed MCAT biology guide and list of subtopics included within these three foundational concepts, check out the AAMC’s guide to what’s on the MCAT exam, and specifically the BBFLS section. Here’s an overview of the main subtopics included in this section of the MCAT: 

Sample MCAT Biology and Biochemistry Questions

MCAT biology practice passages and questions are a great way to start testing your knowledge of MCAT subjects:

Passage:

The myocellular transmembrane Na+ gradient is important for proper cellular function. During septic shock, disruption of Na+ homeostasis often occurs and leads to decreased membrane potential and increased intracellular Na+. It has been found that failure of cellular energy metabolism is a common symptom in septic patients who do not respond to therapeutics. Because normal intracellular levels of Na+ are maintained by the Na+K+ ATPase, it is important to understand how metabolic energy production is linked to cation transport.

Researchers are interested in whether the energy used for ion transport is derived from glycolysis or oxidative phosphorylation. This information would provide a better understanding of myocellular damage that occurs during critical illness. Experiments were conducted to evaluate the effects of glycolytic inhibition on cellular Na+ and K+ concentrations and lactate production in rat skeletal myocytes.

Rat skeletal muscle fibers were extracted and incubated in normal media (control), glucose-free media (G(–)), and glucose-free media with various concentrations of the glycolytic inhibitor iodoacetate (IAA). IAA directly prevents the formation of 1,3-bisphosphoglycerate. After one hour in the media, the muscle tissues were assayed for intracellular Na+ and K+ content and lactate production. Cellular viability was determined by measuring the amount of lactate dehydrogenase (LDH) released, as LDH release is an indicator of cell death.

The results are displayed in Figure 1:

Figure 1: Effects of glycolytic inhibition on intracellular Na+ and K+ content and lactate production with cellular viability measured by LDH release. (Note: The * indicates p < 0.05 versus control.)

The researchers also examined the effect disruption of oxidative phosphorylation had on Na+ and K+ content. Inhibition of oxidative phosphorylation was caused by carbonyl-cyanide m-chlorophenylhydrazone (CCCP), an ionophore that allows protons to move freely through membranes. No correlation between Na+ and K+ content and oxidative phosphorylation was found.

Adapted from: Okamoto K, Wang W, Rounds J, Chambers EA, Jacobs DO. ATP from glycolysis is required for normal sodium homeostasis in resting fast-twitch rodent skeletal muscle. The American Journal of Physiology-Endocrinology and Metabolism. 2001 Sept;281(3):E479-88.

Want help with the biology section of the MCAT? Check out our tips:

Sample Questions and Answers

7. In the figure, the three curves represent hemoglobin oxygen binding at three different pH values, pH 7.2, pH 7.4, and pH 7.6.

Want more MCAT study tips? Watch this video:

Tips for the MCAT Biology Section

Tip #1: Use active learning techniques

Active learning techniques will allow you to absorb, learn and retain the huge amount of information covered in this section more effectively. Use the study methods that work best for you, whether this is using flashcards, mnemonics or other visual learning techniques. Visual learning also helps you with your information recall.

“Writing out any sort of process insteps, anything kinesthetic helped more with [MCAT Biology] … Utilize active learning in content review, draw things out, create mnemonics, and adjust your study tools to match the material so you can learn it more effectively and efficiently. If you are studying glycolysis–a flowchart helps more than putting this entire concept on a flashcard. If looking at differences between insulin and glucagon–a Venn diagram works better than a flowchart. Amino acids can be grouped by properties using mnemonics, but could also be drawn and put in a table.” – Dr. Noah Heichel, DO, WVSOM

Tip #2: Review course content

The MCAT biology section covers a large number of topics and concepts you’ll learn in your introductory biology courses during undergrad. Hold onto those course notes, textbooks and any study materials. You can use them during your MCAT prep. Many students also take the MCAT in their junior year of undergraduate so the concepts covered on the exam are fresh in their minds.

“I had just taken biochemistry in the spring semester preceding my MCAT and had also concurrently taken general biology in the fall, so these were my strongest science sections … I focused on refining my strongest points, reviewing topics I had grasped previously, and focusing on high yield for the items I didn’t know.” – Dr. Monica Taneja, MD, University of Maryland School of Medicine.

Tip #3: Practice applying your knowledge

Textbook and course notes review is only half the strategy you need to ace this section. Apply your learning with regular practice tests. This will help you understand whether your content review is working and you’re truly learning the concepts tested on the MCAT.

“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

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