20 Questions
Which molecule is responsible for stimulating the opening of sodium channels in photoreceptor cells?
cGMP
What enzyme produces cGMP in the photoreceptor?
Guanylyl cyclase
What happens to the membrane potential of photoreceptor cells when cGMP is reduced?
It becomes more negative
What is the pigment in rods called?
Rhodopsin
What is the receptor protein in rods called?
Opsin
What is the prebound agonist in rods called?
Retinal
What is the G-protein called that is stimulated by the bleaching of rhodopsin?
Transducin
What is the effector enzyme activated by transducin?
Phosphodiesterase (PDE)
What does PDE activity do to the cGMP level?
Reduces
What happens to the sodium channels when the cGMP level is reduced?
They close
Which of the following is true about phototransduction in rods?
Phototransduction in rods is a process by which the absorption of light energy is transduced into a change in the photoreceptor membrane potential.
What is the role of G-proteins in phototransduction?
G-proteins in the photoreceptor membrane activate an effector enzyme that changes the cytoplasmic concentration of a second messenger molecule.
What happens when the photopigment in a rod is activated by light?
The activated photopigment in a rod activates G-proteins, which in turn activate an effector enzyme that changes the cytoplasmic concentration of a second messenger molecule.
What is the depolarization of the rod outer segment in complete darkness caused by?
The steady influx of Na through special channels in the outer segment membrane.
What is the membrane potential of a typical neuron at rest?
About -65 mV
What is the membrane potential of the rod outer segment in complete darkness?
About -30 mV
What is the movement of positive charge across the membrane in the dark called?
The dark current
What is the equilibrium potential for K?
About -65 mV
What is the process by which chemical signals are transduced into electrical signals during synaptic transmission called?
Transduction
What is the process by which the absorption of light energy is transduced into a change in the photoreceptor membrane potential called?
Phototransduction
Test your knowledge on phototransduction in rods and understand how light energy is converted into changes in the membrane potential of photoreceptor neurons. Explore the mechanism behind this process and its similarities to chemical signal transduction.
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