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28 Cards in this Set
- Front
- Back
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Components of lens fiber differentiation |
Withdrawal from the cell cycle, elongation, expression of large amounts of proteins (the crystallins), specialization of their plasma membranes and degradation of all membrane-bound organelles |
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Types of crystallins |
Alpha, beta-gamma |
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Function of alpha crystallins as heat shock proteins |
Stabilize proteins that are partially unfolded and prevent them from aggregating (termed “chaperone” activity) |
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Number of subunits in alpha crystallin complexes |
30 |
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Difference between beta and gamma crystallins |
Tendency for β-crystallins to form multimers, while the γ-crystallins exist as monomers |
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Components of lens fiber cytoskeleton |
Microtubules, microfilaments and intermediate filaments |
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Proteins contained in lens intermediate filaments |
Vimentin, filensin and phakinin |
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Binding partner of phakinin in lens beaded filaments |
Filensin |
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Components of lens cytoskeletal microtubules |
Vimentin, actin, tubucin |
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Protein that makes up the lens fiber microfilament network |
Actin |
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Interdigitations between adjacent lens fibers |
Ball and socket junctions |
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Most abundant protein in lens fiber cell membranes |
MIP (Major intrinsic polypeptide) |
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Proteins found in gap junctions between lens fibers |
Connexins |
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Lens vasculature during development |
Tunica vasculosa lentis and anterior pupillary membrane |
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Thickness of anterior lens capsule |
14 micrometers |
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Thickness of the lens capsule at the posterior pole |
2-4 micrometers |
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Thickness of anterior and posterior preequatorial lens capsule |
21 and 23 micrometers respectively |
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Thickness of equatorial lens capsule |
17 micrometers |
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Refractive index of the lens |
1.4 centrally, 1.36 peripherally |
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Composition of lens capsule |
Type IV collagen |
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Site of insertion of zonular fibers |
1.5 mm anterior and 1.25 mm posterior to the equator |
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Area of the anterior lens epithelium with greatest activity of premitotic DNA synthesis |
Germinative zone |
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Enzyme catalysing the phosphorylation of glucose to glucose-6-phosphate |
Hexokinase |
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Key enzyme of the sorbitol pathway |
Aldose reductase |
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Enzyme for the metabolism of sorbitol to fructose |
Polyol dehydrogenase |
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Protein content of the lens |
33% |
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Factors contributing to lens transparency |
Precise organization of the fiber cells, their high protein concentration and the absence of organelles from the fiber cells that lie in the optical axis |
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Cause of brunescent cataract |
High concentrations of chromophores |
