MCAT® Biological and Biochemical Foundations of Living Systems (BBLS)

MCAT® Biological Sciences Overview

Subject Breakdown

The Biological and Biochemical Foundations of Living Systems (BBLS) section is the first section to appear on the MCAT exam is worth 25% of your total score. This section tests your knowledge of fundamental concepts that govern processes unique to living organisms (growing, reproducing, responding, metabolizing, and adapting). Therefore, students need a good understanding of various biological and biochemical concepts to show their proficiency for medical school. 

  • Introductory  Biology - 65%
  • First- Semester Biochemistry - 25%
  • Organic Chemistry - 5% 
  • General Chemistry - 5%

Question Structure

This section contains 10 passages that often include survey details followed by the presentation of the resulting data in the form of tables, graphs, or figures. You will need to interpret the results of the experiment, apply equations, and perform calculations to connect the results to broader scientific concepts.

  • 59 multiple-choice questions.
  • 10 passages each with 4 to 6 associated questions.
  • 15 independent or "discrete" questions.

Timing & Pro Tips

Students have only 95 minutes to complete this challenging MCAT section, and many find this time constraints to be very challenging.

  • Spend less than 3 minutes reading each passage.
  • Don’t get bogged down by small details.
  • Focus on any equations, graphs or tables of results provided.
  • Calculators are NOT permitted, so use rounding and estimation to simplify calculations.
  • Don't forget you have access to the Periodic Table.

Ace The Biological Sciences With Private MCAT Tutoring

There is so much material to learn in the Biological and Biochemical Sciences section that, without proper guidance, you could end up wasting a lot of time memorizing irrelevant facts that are unlikely to ever appear on the test. Knowing the right strategies for each section of the MCAT® is the key to significantly improving your score.

Dr. Stuart Donnelly’s academic credentials and teaching experience are second to none. Stuart has a Ph.D. from Oxford University, 20 years of MCAT® tutoring experience, and is the author of several critically acclaimed test prep books. Many leading educators consider Dr. Donnelly “One of the most qualified and experienced MCAT tutors in the country.”

Over the past two decades, Stuart has developed several unique techniques that help his students deal with the passage-based structure of this section and master each of the background topics in Biology and Biochemistry.

Private MCAT ® Biological Sciences tutoring with Dr. Donnelly is available in person at his San Diego-based office or online via Zoom, so contact Stuart today to schedule your FREE consultation and take your Biological Sciences score to the next level.

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MCAT® Biological Sciences: Concepts Tested

Foundational Concept 1:

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

  • 1A: Structure and Function of Proteins and Their Constituent Amino Acids
  • 1B: Transmission of Genetic Information from the Gene to the Protein
  • 1C: Transmission of Heritable Information from Generation to Generation and the Processes That Increase Genetic Diversity
  • 1D: Principles of Bioenergetics and Fuel Molecule Metabolism

Foundational Concept 2:

Highly organized assemblies of molecules, cells, and organs interact to carry out the functions of living organisms.

  • 2A: Assemblies of Molecules, Cells, and Groups of Cells within Single Cellular and Multicellular Organisms
  • 2B: The Structure, Growth, Physiology, and Genetics of Prokaryotes and Viruses
  • 2C: Processes of Cell Division, Differentiation, and Specialization

Foundational Concept 3:

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.

  • 3A: Structure and Functions of the Nervous and Endocrine Systems and Ways in Which These Systems Coordinate the Organ Systems
  • 3B: Structure and Integrative Functions of the Main Organ Systems