This collection is being developed for the revised MCAT® exam that will first be administered in spring 2015. Videos will be added to the collection through fall 2014. All content in this collection has been created under the direction of the Khan Academy and has been reviewed under the direction of the Association of American Medical Colleges (AAMC). All materials are categorized according to the pre-health competencies tested by the MCAT²⁰¹⁵ exam; however, the content in this collection is not intended to prescribe a program of study for the MCAT²⁰¹⁵ exam. The content is also included in the Pre-health Collection within MedEdPORTAL’s iCollaborative sponsored by the AAMC: www.mededportal.org/pre-health
*MCAT® is a program of the AAMC and related trademarks owned by the Association include Medical College Admission Test, MCAT, and MCAT²⁰¹⁵. For more information about the MCAT exam visit : www.aamc.org/mcat2015
2A: Not all shall pass! Yards have fences, and cells have membranes. You don’t want just anybody waltzing into your backyard. Similarly, a healthy cell doesn’t just let in any random molecule - this is the concept of selective permeability. Some molecules (e.g. steroids) more easily cross the barrier whereas others (e.g. charged ions) have a more difficult time getting inside the cell without a little help from transporters in the membrane.
2A: The human body is composed of about 100 trillion cells (this is not counting your bacterial buddies, who actually outnumber your cells 10 to 1!) Your cells must speak to each other to coordinate this massive symphony of life. In this tutorial, you will learn about the molecular basis of cellular signaling that makes this vast network speedy and efficient.
2A: Each cell in your body has a “membrane potential.” Think of it like rolling a ball to the top of a hill - once the ball is at the top, it is smooth sailing down. Similarly, this electric membrane potential allows ions to flow down a gradient of electrical energy (the inside of the cell is negative relative to the outside). We will discuss this concept as well as other mechanisms for movement of ions, water, and other molecules across cellular membranes.