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Content Update: [MCAT | Test Prep] Biological and Biochemical Foundations of Living Systems (BBLS) Passages


Hi, everyone!

We are thrilled to announce content improvements we have made to the Khan Academy MCAT course! These improvements include passage, question, and explanation updates to over 80 Biological and Biochemical Foundations of Living Systems (BBLS) passages included in the course. The BBLS practice passages can be found in Unit 2 of the Khan Academy MCAT course, titled "Practice Passages: Biological and Biochemical Foundations of Living Systems."

What improvements were made to these passages?

1. Passage organization by foundation and topic: BBLS passages are now organized by foundation and topic, which makes them easier to navigate and aligns them with the video-based lessons in the Khan Academy MCAT course.

An overview of the new BBLS passage organization is shown below:

Foundation 1:
Biomolecules passages
Foundation 2:
Cells passages
Foundation 3:
Organ systems passages

Topics include:

  • Amino acids
  • Enzyme kinetics
  • DNA replication
  • DNA technology
  • Chromosomal abnormalities and gene mutations
  • Genetics (inheritance)
  • Metabolism

Topics include:

  • Organelles
  • Cell membranes
  • Viruses
  • Bacteria
  • Cell cycle and cancer
  • Embryonic development
  • Cell studies

Topics include:

  • Nervous system
  • Neuromuscular junction
  • Muscles
  • Skeletal system
  • Endocrinology
  • Metabolism
  • GI system
  • Cardiovascular system
  • Immune system
  • Renal
  • Skin

2. Passage and question improvements: Updates to the passages have increased the variety of research studies and graphical data included in Khan Academy passages and have better aligned the passage style with the MCAT exam. The updated passages also include more Skill 3 and Skill 4 questions, to offer extra practice with research and data analysis questions.

Examples of research-based figures covered in the new passages are shown below:

3. Explanation improvements: All BBLS MCAT questions now come with helpful hints and clear explanations. Many include helpful images to aid in content learning and graphical analysis. Examples of explanation graphics are shown below:

How should I use the new BBLS passages to study? 

Option 1: Study the BBLS passages, topic by topic, as you progress through the video-based lessons found in units 5-7 of the Khan Academy MCAT course, which cover Foundation 1 (Biomolecules), Foundation 2 (Cells), and Foundation 3 (Organ Systems). This will allow you to learn how to apply MCAT concepts to passages as you study the content.

Option 2: After you’ve completed your BBLS content review, go through the BBLS passages in order. This will provide a valuable review of the content and prepare you for the AAMC practice materials.

Option 3: If you’re limited on time, study only the new BBLS passages covering areas in which you need more support — e.g. if you struggle with nervous system-based questions or content, then find those passages. It will be easy to find specific passages now that BBLS passages are organized by foundation and topic.

Find the new Khan Academy passages at


Happy learning!