MCAT Official Prep (AAMC
Biology Question Pack, Vol 2. Passage 4 Question 24
• Gated ion channels bind a ligand and open a channel through the membrane that allows specific ions to pass through.
• One common location to find gated ion channels is in electrically excitable cells like neurons, where they allow for a rapid change in the membrane potential of the cell.
• While ligand-gated ion channels rely on ligand binding to open, voltage-gated ion channels open in response to a change in membrane potential.
Membrane potential: the difference in electric potential between the inside and outside of a cell, defined by the concentration gradient of positively and negatively charged ions across the plasma membrane.
Allosteric site: a ligand-binding site on a protein that is located away from the active site (in the case of an enzyme) or the ion channel (in the case of a gated ion channel).
Ligand-gated ion channels form a pore through the plasma membrane
Neurotransmitters: chemicals that enable neurotransmission
Plasma membrane: separates the interior of the cell from the outside environment made of phospholipids
Hydrophobic: avoids water
Hydrophilic: likes water
Extracellular: outside the cell
Intracellular: inside the cell
Voltage–gated channels: a class of transmembrane proteins that form ion channels that are activated by changes in the electrical membrane potential