MCAT Biology Questions: The Ultimate Guide

Sample MCAT Biology and Biochemistry Questions

MCAT biology practice passages and questions are a great way to start testing your knowledge of MCAT subjects. Below you will find several Biological and Biochemical Foundations of Living Systems sample questions to test your skills for this section of the MCAT:

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.

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Sample Questions:

1. The researchers chose a concentration of 0.3 mM IAA as the working concentration for any additional studies instead of 1 mM or 2 mM. What is the likely reason for this?

A) The lower concentration of IAA gave the largest Na+ response.

B) Higher concentrations induced significant cytotoxicity.

C) The solubility of IAA was not high enough.

D) The researchers were trying to mimic control conditions as closely as possible.

2. The information in the passage suggests that glycolysis:

A) is important for maintaining normal Na+ and K+ levels in skeletal muscle.

B) facilitates membrane permeability in skeletal muscle.

C) impedes the function of the Na+ and K+ ATPase in skeletal muscle.

D) is regulated by the Na+ and K+ ATPase in skeletal muscle.

3. If the effects of IAA treatment in nerve cells are the same as those observed in myocytes, which feature of an action potential would be most affected by IAA treatment?

A) Initiation of depolarization

B) Rising phase of depolarization

C) Falling phase to undershoot

D) Return to resting potential

4. How is the basal layer of the epidermis and the innermost lining of the small intestine similar?

A) Both are non-dividing tissues.

B) Both are derived from ectoderm.

C) Both are composed of squamous cells.

D) The cells of both are connected by tight junctions.

5. Starting with the translation initiation codon, the following sequence encodes a polypeptide of how many amino acids?

5'-CUGCCAAUGUGCUAAUCGCGGGGG-3'

A) 2

B) 3

C) 6

D) 8

6. Sodium dodecyl sulfate (SDS) contains a 12-carbon tail attached to a sulfate group and is used in denaturing gel electrophoresis of proteins. Numerous SDS molecules will bind to the exposed hydrophobic regions of denatured proteins. The use of SDS in this experiment allows for the separation of proteins by:

A) charge

B) molecular weight

C) shape

D) solubility

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.

What conclusion can be drawn from these data about the oxygen binding of hemoglobin at different pH values?

A) Low pH favors the high affinity oxygen binding state.

B) Low pH favors the low affinity oxygen binding state.

C) Oxygen affinity is independent of pH.

D) Oxygen binding is non-cooperative at low pH.

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Answers to Sample Questions

1. The researchers chose a concentration of 0.3 mM IAA as the working concentration for any additional studies instead of 1 mM or 2 mM. What is the likely reason for this?

A) The lower concentration of IAA gave the largest Na+ response.

B) Higher concentrations induced significant cytotoxicity.

C) The solubility of IAA was not high enough.

D) The researchers were trying to mimic control conditions as closely as possible.

2. The information in the passage suggests that glycolysis:

A) is important for maintaining normal Na+ and K+ levels in skeletal muscle.

B) facilitates membrane permeability in skeletal muscle.

C) impedes the function of the Na+ and K+ ATPase in skeletal muscle.

D) is regulated by the Na+ and K+ ATPase in skeletal muscle.

3. If the effects of IAA treatment in nerve cells are the same as those observed in myocytes, which feature of an action potential would be most affected by IAA treatment?

A) Initiation of depolarization

B) Rising phase of depolarization

C) Falling phase to undershoot

D) Return to resting potential

4. How is the basal layer of the epidermis and the innermost lining of the small intestine similar?

A) Both are nondividing tissues.

B) Both are derived from ectoderm.

C) Both are composed of squamous cells.

D) The cells of both are connected by tight junctions.

5. Starting with the translation initiation codon, the following sequence encodes a polypeptide of how many amino acids?

5'-CUGCCAAUGUGCUAAUCGCGGGGG-3'

A) 2

B) 3

C) 6

D) 8

6. Sodium dodecyl sulfate (SDS) contains a 12-carbon tail attached to a sulfate group and is used in denaturing gel electrophoresis of proteins. Numerous SDS molecules will bind to the exposed hydrophobic regions of denatured proteins. The use of SDS in this experiment allows for the separation of proteins by:

A) charge

B) molecular weight

C) shape

D) solubility

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.

What conclusion can be drawn from these data about the oxygen binding of hemoglobin at different pH values?

A) Low pH favors the high affinity oxygen binding state.

B) Low pH favors the low affinity oxygen binding state.

C) Oxygen affinity is independent of pH.

D) Oxygen binding is non-cooperative at low pH.

How to Prepare for 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.

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

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 pdf on the BBFLS section. Here’s an overview of the main subtopics included in this section of the MCAT: 

To excel in the BBFLS section, you’ll not only need a solid knowledge base in each of these content areas but also the ability to “activate” this foundational knowledge with scientific inquiry and reasoning skills. Understanding how to apply your knowledge of biology and biochemistry to solve complex problems is the key to a great score on this section. However, this complex problem-solving also plays a part in every section utilizing applications of biology, such as the MCAT psychology section. 

If you're wondering when to start studying for the MCAT, you should assess how much knowledge you have retained from your introductory university classes. Below is our guide to how to prepare for the MCAT biology and biochemistry section:

Phase 1: Initial Diagnosis

Before you start to design your MCAT study schedule, you'll need to establish your baseline grasp of the material. To do this, we recommend taking a full-length MCAT diagnostic test. Don’t worry about trying to ace your diagnostic exam though—the goal is just to understand your exact strengths and weaknesses before you embark on your MCAT preparation. For your diagnostic, we recommend using a full-length exam from the AAMC. Complete this practice exam in one sitting, ideally in an environment that mimics test-day conditions. Use the results of your diagnostic test results to guide your MCAT preparations by determining which areas of the biology and biochemistry section you’ll need to focus on the most. 

For example, for the foundational concept of "how highly-organized assemblies of molecules, cells, and organs interact to carry out the functions of living organisms," start by focusing one study session on a specific content category, such as the life cycle of viruses or the mechanisms governing cell differentiation and specialization. Investigate how each topic relates to cell growth and integration to form larger structures that carry out essential biochemical and physiological functions in the body. Use the AAMC’s list of subtopics as a guide and to ensure that there are no gaps in your preparation. 



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Phase 2: Specialized Active Study

After this initial phase of diagnosis and review, you'll want to begin the more active phases of your study. Active study strategies are simply those that have you doing more than passively reading and reviewing. Taking subject-specific practice exams to better target your weaknesses is a good option. You can either design these yourself or utilize premade practice materials from the AAMC. UWorld and other question bank services also have both multi-section and targeted practice exams as well, and these can be used both for periodic progress-checking and daily practice. You should also learn how to read MCAT graphs and practice with these visuals so you’re comfortable with them come test day. A great deal of the data and information on the biology section of MCAT will be presented visually or in some kind of graph.

The key is to use as many learning strategies and modules as possible. While some tactics may not work for your learning style, try to utilize as much variety as you can. Other forms of active study include flashcards, writing summaries of material you've reviewed in your own words, group study/quizzing sessions, and even explaining concepts to friends and family who aren't as familiar with biology or medicine. An often-overlooked tactic is to schedule non-MCAT reading throughout your months of preparation in order to strengthen your MCAT reading comprehension and analysis skills. The point is to create a kind of infrastructure so you can recall and use the knowledge you've learned and reviewed in the previous phase—think of it like building highways so these pieces of information can travel to where you need them to go on exam day. 

At the end of this phase, check your progress by taking your next full-length MCAT practice test. Put your MCAT score into perspective and look up MCAT test and release dates that align with where you stand in your preparation. After this second practice exam, it's time to move into to the third, active-practice phase of your MCAT prep: at least 70% of your study time in the final months of preparation should be spent completing MCAT practice questions. 

Phase 3: Time management and practice tests

The MCAT is a marathon exam and the biology and biochemistry section is right in the middle of this marathon. The total seated time for the MCAT is just over seven and a half hours for students that use the optional breaks between sections. By the time you get to the biology and biochemistry section of the MCAT, you will have been at the testing center for at least four hours. This is already longer than even the lengthiest exams or standardized tests you’ll have encountered thus far in your academic career. Your success on test day depends on your ability to stay focused and improve your MCAT timing.  

In this final phase use your study and practice-question time to build up your endurance so you can remain focused for over seven hours of testing. It’s difficult and quite a grind, but you must develop the ability to sit and study/answer questions for 95 minutes straight. Once you can manage a single unbroken 95-minute session, expand this to four 95-minute periods in a row with short breaks (20-30 minutes) in between—just like test day. Keep the metaphor of a marathon in mind: runners become proficient not by trying and failing to run 26 miles until success finally arrives, but by gradually increasing their stamina and work capacity in a logical and structured manner. Your brain isn’t technically a muscle, but intensive cognitive work like these functions much the same way.

Check out these study tips for the MCAT Biology section:

Tips For Answering Biology and Biochemistry Questions on the MCAT 

Now that we've discussed general and long-term strategies for studying and preparation, let's get into the nitty-gritty on just how to approach the BBFLS section as you begin grinding through your practice questions. 

Tip #1: Understand the Skills Being Tested 

When you read through MCAT prep questions—whether in practice or on test day—you should begin by identifying the question type by what skill it's testing. The AAMC lists four skills that are tested throughout the test: 

1. Knowledge of scientific concepts and principles.
2. Scientific reasoning and problem-solving.
3. Reasoning about the design and execution of research.
4. Data-based and statistical reasoning.

By determining exactly which of these skills is being tested, you can better orient yourself as you retrieve relevant information. For instance, if a question seems to be asking you to explain or elaborate some aspect of research design, you can narrow down your focus and not bother considering answers about concrete knowledge of scientific concepts. You don’t need to waste ten minutes straining to recall every stage of the Krebs cycle in order to answer a question about measuring glucose levels in a fermentation experiment. Understand that while the MCAT is a broad and extensive test, it does have structures that repeat throughout, and being able to identify these can not only improve the quality of your response but also how quickly you’re able to commit to it and move on to the next question. 

Tip #2: Mimic the Resources Available on Test Day 

You will not have access to a calculator during the MCAT. However, you will have access to a periodic table of elements throughout the test. It is important that you complete practice questions under conditions that will mimic those of test day as you prepare. If you won’t have a calculator during the MCAT, don’t practice with a calculator! If you will be given a periodic table, be sure to understand how to use it to your full advantage. It will be most helpful to complete your practice with the identical version of the periodic table that you will have on test day, which provides the name, atomic mass, and atomic number of each element; this version of the periodic table can be found on the AAMC website. During the actual test, you’ll also be given a notebook of laminated graph paper and a non-permanent marker to use for writing notes and equations. If these tools are unfamiliar to you, we recommend obtaining similar materials during your preparation so it’s not such a stark shift on test day. Feeling frustrated by hitherto alien writing implements on such an important and grueling day of testing is totally avoidable. Give yourself time to acclimate to the known elements of your test-taking environment, and you’ll be much more able to adapt to any totally unforeseen circumstances like weird ambient sounds or lighting. 

Tip #3: Be Ready for Data & Experiments 

The AAMC incorporates biology and biochemistry experiments into the MCAT, which means that you can't just practice vocabulary: come test day, you must be able to apply your knowledge to experiment-style questions. Be sure to review key experimental techniques, such as gel electrophoresis and polymerase chain reaction. As you complete practice passages, get into the habit of determining the independent and dependent variable for the experiment, as well as necessary controls. When completing the biology and biochemistry section of the MCAT, you should not spend too much time on a graph or figure within a passage, unless a question specifically asks about it. However, as you practice, you'll want to sharpen your analysis skills in the event that you need them. How can you ensure that you get enough practice interpreting data and graphs? Once you finish a practice passage, take some time to return to any graphs or figures and review them to fully understand the information presented. This practice will ensure efficiency during the test day crunch time. 

Tip #4: Build Your Confidence 

Confidence is a key factor in both improving your score and performing well on test day. In addition to the Biological and Biochemical Foundations of Living Systems section, biology will also be assessed in the Chemical and Physical Foundations of Biological Systems section and the Psychological, Social, and Biological Foundations of Behavior section. In chemistry and physics, you will be asked how chemical and physical factors interact with biology. In psychology and sociology, you will need to understand how biological factors can impact behavior. Neither of these MCAT sections are focused on biology, but you'll find that biology is a major theme that runs through the entire exam. Don’t underestimate the power of confidence in your biology knowledge base and in your test taking strategies!  

Confidence promotes a consistent pace as you move through passages and helps to prevent second-guessing on answer choices. If there is a particular biology or biochemistry topic that has been challenging for you in the past, tackle it head-on during your MCAT prep. Delve deep into the topic repeatedly until you feel comfortable and confident with it. This will prevent negative past experiences from derailing your confidence on test day. As you approach your exam, remind yourself that you have worked extremely hard to prepare for the MCAT and that this will surely be reflected in your score.  

Another way to build confidence is to teach the concepts to a friend. You know you've mastered the material when you can successfully teach someone else. Try this whenever possible, especially with topics in biology and biochemistry that you found initially challenging. Did your temporary student understand it? If so, you probably have it down! There's also the tried-and-true method of creating flashcards with key questions on one side and answers on the other. These are easy to make and incredibly helpful to check your knowledge on any given topic. Keep in mind that lots of companies sell flashcards, but it’s far more effective to make them yourself as it allows for active learning during their construction as well as when you're studying with them. Additionally, you can tailor these to your specific strengths and weaknesses, making more for your blind spots and fewer for those areas you know inside and out.  

Conclusion

It is important to appreciate that the Biological and Biochemical Foundations of Living Systems section of the MCAT is an important piece of your medical school application. The BBFLS section spans a wide range of academic disciplines that form the framework for your medical school studies and for your success as a physician. The MCAT is viewed as a strong predictor of student success, so get ready to delve into studying and to demonstrate to admissions committees that you really know your stuff! 

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