Chemical and Physical Foundations of Biological Systems Section: Content Category 4C

Electrochemistry and electrical circuits and their elements
Charged particles can be set in motion by the action of an applied electrical field, and can be used to transmit energy or information over long distances. The energy released during certain chemical reactions can be converted to electrical energy, which can be harnessed to perform other reactions or work.

Physiologically, a concentration gradient of charged particles is set up across the cell membrane of neurons at considerable energetic expense. This allows for the rapid transmission of signals using electrical impulses — changes in the electrical voltage across the membrane — under the action of some external stimulus.
The content in this category covers electrical circuit elements, electrical circuits, and electrochemistry. The topics and subtopics are below.

Topic Level Key:

The abbreviations found in parentheses indicate the course(s) in which undergraduate students at many colleges and universities learn about the topics and associated subtopics. The course abbreviations are:
BIO = two-semester sequence of introductory biology
GC = two-semester sequence of general chemistry
PHY = two-semester sequence of introductory physics
Please note topics that appear on multiple content lists will be treated differently. Questions will focus on the topics as they are described in the narrative for the content category.

Electrostatics (PHY)

  • Charge, conductors, charge conservation
  • Insulators
  • Coulomb’s Law
  • Electric field E
    • Field lines
    • Field due to charge distribution
  • Electrostatic energy, electric potential at a point in space

Circuit Elements (PHY)

  • Current I = ΔQ/Δt, sign conventions, units
  • Electromotive force, voltage
  • Resistance
    • Ohm’s Law: I = V/R
    • Resistors in series
    • Resistors in parallel
    • Resistivity: ρ = R⋅A / L
  • Capacitance
    • Parallel plate capacitor
    • Energy of charged capacitor
    • Capacitors in series
    • Capacitors in parallel
    • Dielectrics
  • Conductivity
    • Metallic
    • Electrolytic
  • Meters

Magnetism (PHY)

  • Definition of magnetic field B
  • Motion of charged particles in magnetic fields; Lorentz force

Electrochemistry (GC)

  • Electrolytic cell
    • Electrolysis
    • Anode, cathode
    • Electrolyte
    • Faraday’s Law relating amount of elements deposited (or gas liberated) at an electrode to current
    • Electron flow; oxidation, and reduction at the electrodes
  • Galvanic or Voltaic cells
    • Half-reactions
    • Reduction potentials; cell potential
    • Direction of electron flow
  • Concentration cell
  • Batteries
    • Electromotive force, Voltage
    • Lead-storage batteries
    • Nickel-cadmium batteries

Specialized Cell - Nerve Cell (BIO)

  • Myelin sheath, Schwann cells, insulation of axon
  • Nodes of Ranvier: propagation of nerve impulse along axon

To support your studies, see the following video tutorials below from the Khan Academy MCAT Collection. The videos and associated questions were created by the Khan Academy in collaboration with the AAMC and the Robert Wood Johnson Foundation.