What’s Tested on the MCAT: The Biology Section

The MCAT (Medical College Admission Test) is a standardized test that assesses a candidate’s readiness for medical school. One of its most important sections is the Biological and Biochemical Foundations of Living Systems. This section, often referred to as the “Biology” section or BB, is one of the three science sections on the MCAT. These sections are designed to test the examinee’s understanding of fundamental biological and biochemical concepts within a (usually human) biological context.

The MCAT places a considerable emphasis on critical thinking and scientific reasoning over rote memorization. This approach reflects the skills necessary for success in medical school and beyond. Here’s a breakdown of how the questions are distributed across different skill sets:

• Scientific reasoning and problem-solving: 45%
• Scientific knowledge of concepts and principles: 35%
• Reasoning about the design and execution of research: 10%
• Data-based and statistical reasoning: 10%

This means that approximately 65% of the questions are geared towards evaluating your problem-solving abilities and scientific reasoning skills rather than just your knowledge of scientific facts

Number of Questions / Time per Question

The Biology section comprises 59 questions that need to be completed in 95 minutes, giving you an average of approximately 97 seconds per question. Including the time it takes to read the passages, that drops to an average of 50-60 seconds per question. Efficient time management and the ability to quickly analyze and interpret information are crucial to performing well and getting a good MCAT score.

Types of Questions and Skills Tested

• Passage-Based Questions: 44 of the 59  questions are based on passages that describe experiments, studies, or scenarios. These require you to apply your scientific knowledge and reasoning skills to new information.
• Discrete Questions: 15 of the 59 questions are standalone, testing specific knowledge areas without the context of a passage.

Core Biology Subjects Tested

The content of the Biology section spans several core subjects, which typically align with the material covered in first-year university courses. As per the AAMC, the questions are expected to be distributed as follows:

• Biochemistry: 25% or ~15 questions
• Biology: 65% or ~ 38 questions
• General Chemistry: 5% or ~3 questions
• Organic Chemistry: 5% or ~ 3 questions

Scientific Inquiry and Reasoning Skills

This section evaluates your ability to use scientific inquiry and reasoning skills, including:

• Knowledge of Scientific Concepts and Principles (35% of questions)
  • Demonstrating a thorough understanding of scientific concepts and principles.
  • Identifying and explaining the relationships between closely related scientific concepts.
• Scientific Reasoning and Problem-Solving (45% of questions)
  • Applying reasoning skills to scientific principles, theories, and models.
  • Analyzing and evaluating scientific explanations and predictions critically.
• Reasoning About the Design and Execution of Research (10% of questions)
  • Understanding key components of scientific research.
  • Reasoning about and addressing ethical issues in research.
• Data-Based and Statistical Reasoning (10% of questions)
  • Interpreting patterns and trends in data presented in tables, figures, and graphs.
  • Drawing logical conclusions and making inferences from data.

Mathematical Concepts and Techniques

As outlined in the scientific inquiry and reasoning skills section above, some questions will require you to analyze and manipulate scientific data. While the MCAT focuses more on conceptual understanding, basic mathematical skills are necessary for interpreting data and solving problems. Certain MCAT questions will require you to demonstrate your ability to:

• Perform arithmetic calculations involving probability, proportion, ratio, percentage, and square-root estimations.
• Understand exponentials and logarithms (both natural and base 10), scientific notation, and solve simultaneous equations at an Algebra II level.
• Recognize and interpret different scales (linear, semilog, log-log) and calculate slopes from figures, graphs, and tables.
• Use and convert metric units within the metric system and between metric and English units (conversion factors provided when necessary), as well as perform dimensional analysis (balancing equations using units).
• Understand the significance of digits and use reasonable numerical estimates in measurements and calculations.
• Understand vector addition and subtraction and the right-hand rule (knowledge of dot and cross products is not required).
• Understand basic trigonometric concepts: definitions of sine, cosine, tangent, and their inverses; sin and cos values for 0°, 90°, and 180°; and the relationships between the sides of right triangles with angles of 30°, 45°, and 60°.

Will I Have Access to the Periodic Table of the Elements?

Yes, during the MCAT, you will have access to a periodic table to solve the general chemistry and biochemistry questions..

Breakdown of High-Yield, Medium-Yield, Low-Yield

High-yield MCAT topics are essential concepts and subject areas that frequently appear across multiple sections of the test. Mastering these topics is crucial for achieving a competitive score—they are termed “high-yield” because focusing on them can significantly improve your performance.

Luckily, you don’t have to guess which topics to prioritize. According to a March 2024 article by the American Medical Association, the following content areas are identified as potential high-yield categories.

As a quick overview, the high-yield biological science topics are: 

• Protein biochemistry
• General cell biology
• Enzymes
• Amino acids
• DNA
• Molecular biology.

Additional reading: Why is the MCAT challenging for science students?

Foundational Concepts

Foundational Concept 1 (55% of questions):

Biomolecules and Cellular Processes

• Structure and function of proteins and amino acids.
• Genetic information transmission from genes to proteins.
• Heritable information transmission and genetic diversity processes.
• Bioenergetics and metabolism of fuel molecules.

Foundational Concept 2 (20% of questions):

Molecular and Cellular Organization

• Assemblies of molecules, cells, and cell groups in single and multicellular organisms.
• Structure, growth, physiology, and genetics of prokaryotes and viruses.
• Processes of cell division, differentiation, and specialization.

Foundational Concept 3 (25% of questions):

Systems Integration and Homeostasis

• Structure and functions of the nervous and endocrine systems and their coordination of organ systems.
• Structure and integrative functions of main organ systems.

Yes, biology-related questions are not confined to the Biology section alone. For example:

• The Chemical and Physical Foundations of Biological Systems section includes about 5% of questions related to biology.
• Similarly, the Psychological, Social, and Biological Foundations of Behavior section also devotes around 5% of its questions to biology-related topics.

Understanding the content and structure of the MCAT Biology section is essential for your preparation and success on the exam. This section, a cornerstone of the MCAT, evaluates not just your knowledge of biological and biochemical concepts but also your ability to apply scientific reasoning and problem-solving skills. With a strong focus on high-yield topics and foundational concepts, mastering this section can significantly boost your overall score.

To perform well, prioritize high-yield topics such as protein biochemistry, cell biology, enzymes, amino acids, DNA, and molecular biology. Additionally, hone your skills in scientific inquiry, data analysis, and basic mathematical techniques. Remember, efficient time management and the ability to quickly interpret and analyze information are crucial.

By thoroughly understanding and preparing for these aspects, you can confidently tackle the Biology section and move closer to achieving your goal of medical school admission. For further guidance, explore our High-Yield MCAT Topics Guide and detailed articles on foundational MCAT concepts.

And remember, if you have and MCAT-related questions, we’re here to help! Book a free consultation with one of our MCAT experts.

Good luck!