Biochemistry of Vision

Question 1

processing of visual signals

Answer 1

photoreceptors to interneurons to ganglion cells

Question 2

ganglion cells

Answer 2

output cell of the retina
axons form optic n
project to the brain
information transmitted by action potentials

Question 3

rods

Answer 3

night vision
rhodopsin cannot detect color
high sensitivity and low spatial resolution

Question 4

cones

Answer 4

color detection
three opsins (red, green, blue)
low sensitivity and high spatial resolution

Question 5

dark

Answer 5

Na channels are open and cell is DEPOLARIZED

Question 6

light

Answer 6

Na channels are closed and the cell is HYPERPOLARIZED

Question 7

color blindness

Answer 7

rearrangements leads to loss of visual pigment genes or formation of hybrid pigment genes that encode photoreceptors w/ anomolous absorption

Question 8

macular degeneration

Answer 8

high RQ, high lipid content, UV rays

xanthophylls

Question 9

vitamin A metabolism deficiency

Answer 9

night blindness
xerophthalmia
keratinization of epithelium in GI, respiratory, and GU tract
skin becomes dry and scaly

Question 10

retinoid cycle

Answer 10

Rod cell - 11 cis changed to all tras
Retinal pigmented epithelium - uptake of all trans to 11 cis
Rod cell - uptake 11 cis and addition of schiff base to make functional rhodopsin

Question 11

energy transduction

Answer 11

light activated phodopsin
G protein is activated leading to production of cGMP
cGMP opens VG channel allowing Na in and depolarization

Question 12

activation

Answer 12

decrease in cGMP closing ion channels

Question 13

recovery

Answer 13

decrease in Ca
increase in guanylate cyclase activity
increase cGMP