Lens Characteristics Flashcards
The lens is
- is transparent
- a passive structure that us relatively isolated
- absence of blood flow
Lens size throughout life
Grows in size and mass throughout life and does not shed cells
- accumulated post-synthesis modified components disrupt lens clarity
- several forms of accumulated materials give rise to a variety of cataract types
Lens composed of
2/3 water
1/3 protein
Types of metabolism in th Elena
- most simple sugars can be metabolized, but glucose is predominant
- lipids and AA are shown to be metabolized in lens culture
- it seems likely that ketone bodies could be utilized for energy production, but they are note a primary source
Cholesterol in the eye
Makes the lens capsule rigid
Anaerobic glycolysis in lens
Most active energy metabolism in the lens
HMP shunt in the lens 1A
Secondary producing NADPH and ~5-10% of lens energy
The rest of the energy associated with lens metabolism
Energy derived from the metabolism fo lactic acid and glucose in lens epithelium cells that utilize TCA cycle and ET
What factors contribute to the need for tightly regulated energy metabolism that predominantly involves glucose metabolism
- absence of blood flow
- grows in size and mass throughout life and does not shed
- composed of 2/3 water and 1/3 protein
Glucose is obtained from the _________ for the lens
Posterior or anterior lens surfaces that contacts other mediums such as the aqueous humor
How is glucose taken up in the lens
By facilitates transport, however it is not known if insulin plays regulatory role
Transport of glucose among cells in the lens
Accomplished via a network of low resistance gap junctions between cells
Gap junctions in the lens and glucose
Gap junction allows for efficient distribution of glucose, even to lens cells buried deep toward the center of the lens
How much glucose and oxygen gets to the lens from the aqueous
Not much
Why is the lens unaffected by low O2 in aqueous
Due to its reliance on anaerobic glycolysis for energy
