MCAT Biology Questions: Practice Set and Expert Tips

MCAT Biology Questions: Practice Set

Start with these MCAT biology questions before reviewing the explanations. The passage-based questions test your ability to connect biology content with experimental design, data interpretation, and scientific reasoning. The discrete questions test high-yield biology and biochemistry concepts that often appear in the Biology and Biochemical Foundations of Living Systems section.

Before checking the answers, try to answer each question under timed conditions. For passage-based MCAT biology questions, focus on three things: what concept is being tested, what the experiment is measuring, and which answer is best supported by the passage or figure. Practicing practice passages will help you to improve your MCAT score.

MCAT Biology 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.

Sample MCAT Biology Questions and Answers

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.

Check your answers below!

Want more help turning MCAT content review into stronger practice performance? Watch this video:

What MCAT Biology Questions Test 

MCAT biology questions in the Biology and Biochemical Foundations of Living Systems section test your ability to apply introductory biology, general chemistry, organic chemistry, and first-semester biochemistry concepts to scientific passages and discrete questions. The hardest part is often not recognizing the topic; it is figuring out what the question is asking you to do with the information.

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.

“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

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: 

How to Approach MCAT Biology Questions

Tip #1: Turn Content Review into Question Review

For MCAT biology questions, content review is only useful if you can apply it to a passage, figure, or experimental setup. After each missed question, identify whether the mistake came from missing content knowledge, misreading the passage, misunderstanding the figure, or choosing an answer that was too broad or unsupported. This turns each practice question into a targeted review task instead of another round of passive memorization.

“Writing out any sort of process in steps, 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

Tip #2: Review the Concept Behind the Question

When you miss an MCAT biology question, do not only memorize the correct answer. Ask which concept the question was really testing: amino acids, enzymes, genetics, metabolism, cell biology, organ systems, membranes, or experimental reasoning. Your goal is to connect each missed question to a specific weakness so your MCAT prep is more focused.

For a broader review of which topics deserve the most attention, use our guide to high yield MCAT topics instead of trying to study every biology detail with equal weight.

“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

Tip #3: Practice Passage-Based Reasoning

Many MCAT biology questions are not asking whether you can repeat a definition. They ask whether you can use biology knowledge to interpret an experiment, graph, result, or unfamiliar scenario. When reading a passage, pause after each paragraph and ask: What is being tested? What changed in the experiment? What was measured? What conclusion is supported by the data?

If you need a full preparation plan, review our MCAT study schedule rather than trying to build your timeline from practice questions alone.

“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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