EK Biology Chapter 4: Rhodopsin is made of a protein bound to a prosthetic group called retinal. The photon isomerizes retinal causing the membrane of the rod cell to become less permeable to sodium ions and hyperpolarize. Hyperpolarization is transduced to an action potential and the signal is sent to the brain. Picture on p.97 Dark / rod cell depolarized: ·. .Na+ channels open, . .inactive rhodopsin,. .glutamate released ·. .bipolar cell either inhibited or excited, depending on glutamate receptors Light / rod cell hyperpolarized: ·. .Na+ channels close,. .active rhodopsin, ..bipolar cell either released from inhibition or suppressed, depending on glutamate receptors I do not fully understand. What I gather: If light is present, photons isomerize retinal. This makes the membrane of the rod cell less permeable to sodium ions. Na+ channels close. Hyperpolarization occurs. So how does rhodopsin get activated when Na+ channels close? Where are glutamate (and glutamate receptors) involved?