Lecture 22: Phototransduction Flashcards
What opsin is found in rods?
Rhodopsin
Rods have ____ sensitivity and ____ spatial resolution.
Rods have high sensitivity and low spatial resolution.
What opsins are found in cones?
Three opsins: red, green, and blue
Cones have ____ sensitivity and ____ spatial resolution.
Cones have low sensitivity and high spatial resolution.
What portion of the photoreceptor is connected to the bipolar cell?
Inner Segment
What is included in the GPCR system of the outer segment of photoreceptor cells?
Opsins
Transducin
cGMP phosphodiesterase
What is included on the surface membrane of the outer segment of photoreceptor cells?
cGMP gated Sodium Channels
Sodium/Calcium exchanger
Guanylate cyclase
What happens to cGMP gated Sodium Channels in the dark?
They are open and cells are depolarized
What happens to cGMP gated Sodium Channels in the light?
They are closed and cells are hyperpolarized
What AA is found in the center of the 7TM receptor?
Lysine-296
What is the difference between the Schiff base and protonated Schiff base of Retinal bound rhodopsin?
Protonated Schiff base absorbs >440 nm
-active player for signal transduction
What happens when photon when light contacts 11-cis retinal?
11-trans-retinal, kicking off the entire signal transduction pathway
What is the inheritance pattern of colorblindness?
X-linked
Gt activation by light activates what?
cGMP Phosphodiesterase
What happens when there is low cGMP?
Hyperpolarization of visual cells –> visual signal transduction
What can cause signal termination?
- Rhodopsin Kinase
- Rapid hydrolysis of ATP to ADP
- Elevated levels of cGMP
What are consequences of Vitamin A deficiency?
Night blindness Xerophthalmia Keratinization of epithelium Dry, scaly skin AMD Blindness in children Cornea issues Increased likelihood of dying from infections
What are bitot spots?
Build up of keratin in conjunctiva (looks foamy)
What is xerophthalmia
Abnormal dryness of conjunctiva and cornea of the eye with inflammation and ridge formation
What are the two cellular systems of the retinoid cycle?
Photoreceptors Pigmented Epithelium (RPE)
What are two important proteins in the retinoid cycle?
LRAT
RPE65
What is macular degeneration?
Degeneration of RPE and retina that can result in vision loss
