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10 Cards in this Set
- Front
- Back
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The cornea metabolizes 65% of its glucose through the hexose monophosphate shunt. How is the shunt beneficial to cells, and why is this particularly an issue for the cornea?
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The hexose monophosphate shunt in useful in producing NADPH
-The NADPH is used to reduced glutathione -Reduced glutathione is used to control oxidative damage ---> Oxidative damage is a serious issue in corneal tissue because the amount of oxygen that interacts with the cornea. ---> The cornea is very permeable to O2 |
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The retinal pigment epithelium is crucial for retinal function. Name three ways the RPE supports vision.
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1. Absorbs light to prevent reflections back on the photorecetors
2. Mediates transport of nutrients from the blood to the retina 3. Helps recycle all-trans-retinal to 11-cis-retinal |
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Understand the process by which light is detected and converted into a chemical signal at the synapse between the photoreceptor and the bipolar cell.
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Visible light converts rhodopsin through several short lived intermediates to metarhodopsin II which is the active conformation that can interact with the heterotrimeric G-protein transducin
-Mearhodopsin II dissociates into opsin and all trans retinal -All trans retinal is converted to all tran retinol in the photoreceptor and then transported to the RPE where it can be recycled |
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What is the role of Transudcin?
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Transducin exchanges GDP to GTP
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What does GTP causes?
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GTP causes the T-alpha subunit to dissociate from the T-beta/gamma subunit
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What does the T-alpha subunit do?
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T-alpha interacts with the two regulatory gamma subunits of phosphodiesterase--->causing the release of the catalyitically active alpha.beta dimer of PDE---> the active alpha/beta dimer of PDE converts cytoplasmic cGMP to 5-GMP
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How does hyperpolarization of the photoreceptor lead to a synaptic signal?
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Lowering the cytoplasmic concentration of cGMP closes the SODIUM channel
---> this leads to hyperpolarization of around -35 mV ---> Reduces glutamate release |
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What percentage of photoreceptors are cones?
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Approximately 6% of cones are photoreceptors within the retina
---> EXCEPT IN THE FOVEA CENTRALIS (ITS ALL CONE) |
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How do cones detect different colors?
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Cones detect different colors based on the absorption spectrum.
-Blue (420 nm) -Green (535 nm) -Red (565 nm) The protein components of each cone color receptor differs |
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Be able to name two other ways cones differ from rods.
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Cones have faster response time than Rods
Cones are better at detecting rapid events Rods have Greater Sensitivity to light |
