Unsorted Sorry
Eye: composed of living tissues that have energy/material needs met through metabolic pathways
Clarity: no obstructions
Purity: no color interference
Filtering: no visual artifacts:
Anatomy of Eye: Cornea, Lens, Vitreous Humor, Fovea Centralis, Retina, Anterior Chamber
Eye Fluids
Tears – exterior of cornea
Aqueous humor – interior of cornea
Salts, albumin, globulin, glucose, others…
Brings nutrients to lens and removes metabolic waste
Vitreous humor – gelatinous
1)Cornea – part of CNS High Glutathione Reductase
Primary fuel is GLC
.65 ATP PPP – interconversion to provide glycolysis intermediates
.3 ATP glycolysis
*Glutathione Reductase
Permeable to O2 - Generation of ROS
2)Lens – alive, metabolically active Growth (AV) - Crystallins: proteins that make the lens
Anaerobic glycolysis: peripheral cells
.85 Glycolysis
.1 PPP
.03 TCA
Aqueous humor supports - Nutrients and waste
*Grows continually from the periphery
0-80 lens: 3X INC size and 1.5X INC thickness
Epithelia surrounding lens makes enzymes, albuminoids and membrane proteins
Protection – proteins must remain clear and crystalline
NaK pumps, glutathione, protein synthesis, other metabolic events
Sensitive to – redox, osmolarity, high [metabolite], UV radiation
Diseases/Conditions:
1) Presbyopia: (normal) loss of near vision
Due to the normal increases of size and thickness of lens
2) Cataracts only known disease of lens
Light scattering properties develop in the lens
2a Senile cataracts - Age related
Rearrangement of proteins in the lens
Breakdown of protein molecules
Treatment: none
2b Diabetic cataracts INC osmolarity
Activity of aldose reductase & polyol (aldose) dehydrogenase from elevated GLC
INC sorbitol (unused and accumulates) d’s osmolarity
Treatment: none
3)Retina Rods/Cones (VS) – AnaGlycolysis = Lactate Dehydrogenase
Anaerobic glycolysis
Anatomy:
Macula – center of retina
Fovea centralis – center of the macula: spot of greatest visual actuity
Avascular
*Lactate dehydrogenase – uses NADH/NADPH
Rods and Cones: ?mitochondria?, photoreceptor cells
Not outer segments where visual pigments are located
Proteins contain the prosthetic group: 11-cis-retinal
NOT an ALL OR NOTHING event - Graded intensity from
Change in -30 mV steady state to -35 mV \
Number of RODS fired
CONES – Color & Rapid – RBG 11-cis-retinal
11-cis-retinal but different pigments (red, blue, green)
Differences btwn the three color pigments are very fine due to the slight variations of chemical environments
RODS – Low light & Sensitive – Rhodopsin
Detect a signal as low as 5 photons.
Concept #1 Biochemistry of Vision
Function:
Vision
PHASES
1)Light enters eye through lens
2)Light reaches the outer segment of rods and cones to begin SigTrns
3)Pigmented Epithelial Layer absorbs excess light and prevents reflection.
STAGES
a)Photochemical
b)Kinetic
c)Biochemical
d)Electrical
Details:
0) Photon strikes rod
1) 11-cis-retinal -(photon)- trans-retinal KINETIC/MECHANICAL EVENT (quick)
1a Creation of Metarhodopsin
Active molecule, 1/2L 60 s
1b Dissociation of Opsin and trans-retinal
1c Restoration of 11-cis-retinal
2) Metarhodopsin complexes with Transucin BIOCHEMICAL EVENT
Transducin: G-protein
Alpha (Talph) activates phosphodiesterase (PDE)
3) cGMP -(PDE)- 5’GMP ELECTRICAL EVENT
Closes Na channels, changes in MEMpot
4) Metarhodopsin acted by rhodopsin kinase TERMINATION/RESET
Product has high affinity of arrestin, NOT bind to transducin
Allows ONE cycle
5) Hydrolysis of Pi restores the arrestin ?soon the rhodopsin?
