AP Biology Questions on the Blood-Brain Barrier: Exam Prep

🧠 Quick Study Guide

• 🧱 Structure: The BBB is formed by specialized endothelial cells in brain capillaries, connected by tight junctions.
• 🛡️ Function: It selectively restricts the passage of substances from the bloodstream into the brain, protecting it from toxins and pathogens.
• 🚚 Transport Mechanisms: Substances cross the BBB via:
  • Passive diffusion (small, lipophilic molecules)
  • Active transport (glucose, amino acids)
  • Receptor-mediated transcytosis (large molecules like insulin)
• 🚫 Excluded Substances: Large molecules, highly charged molecules, and most bacteria cannot cross the BBB.
• 🌟 Clinical Significance: BBB disruption is implicated in neurological disorders like multiple sclerosis, Alzheimer's disease, and stroke.

🧪 Practice Quiz

1. Which of the following cell types is primarily responsible for forming the blood-brain barrier?
   1. Astrocytes
   2. Ependymal cells
   3. Endothelial cells
   4. Microglia
2. What type of intercellular junction is most critical in establishing the tight barrier function of the BBB?
   1. Gap junctions
   2. Adherens junctions
   3. Desmosomes
   4. Tight junctions
3. Which of the following molecules can typically cross the blood-brain barrier via passive diffusion?
   1. Glucose
   2. Large proteins
   3. Small, lipophilic molecules
   4. Ions
4. Active transport mechanisms at the BBB are essential for the passage of which of the following?
   1. Antibodies
   2. Glucose
   3. Chemotherapeutic drugs
   4. All of the above
5. Receptor-mediated transcytosis is crucial for the transport of which of the following across the BBB?
   1. Small ions
   2. Large proteins like insulin
   3. Lipid-soluble drugs
   4. Water
6. Disruption of the blood-brain barrier is implicated in the pathogenesis of which neurological disorder?
   1. Parkinson's disease
   2. Alzheimer's disease
   3. Multiple sclerosis
   4. All of the above
7. Which of the following characteristics would LEAST favor a drug's ability to cross the blood-brain barrier?
   1. High lipophilicity
   2. Small molecular size
   3. High polarity
   4. Presence of specific transporters