The lens and vitreous Discussion

The lens and vitreous Discussion
The lens and vitreous Discussion
1 The lens
A Is avascular
B Reaches full size at age 18
C Absorbs UV light
D Receives all its nutrition from the aqueous
E Is commonly dislocated in homocysteinuria
2 Regarding the lens
A The lens is 33% protein
B The lens contains more protein than muscle
C The proteins are 55% albumin
D Alpha crystallin is the commonest crystallin
E Gamma crystallin is the largest crystallin
3 The lens
A Will swell if placed in a hypertonic solution
B Has an osmolarity greater than aqueous
C Has an electronegative potential
D Contains a high level of Na
E Contains a low level of K
4 Regarding lens proteins
The lens and vitreous Discussion
A Lens proteins are normally immunologically isolated
B Exposure leads to type II sensitivity
C Antigenic membrane material alone is sufficient to initiate
sensitivity
D The second eye is always affected if proteins from the first are
exposed
E Chemically denatured lens protein can initiate sensitivity
5 Glutathione
A Is synthesized in the lens
B Is in increased levels in the lens nucleus
C Is a polypeptide of glycine, lysine and glutamic acid
D Requires NADPH, if it is to be maintained in a reduced state
(GSH)
E A decrease in the level of GSH precedes disruption of lens
fibre membranes
6 Regarding lipids in the lens
A The lens contains 10% lipids by dry weight
B The majority of lipids are glycosphingolipids
C Cholesterol is locally produced
D 50% of cholesterol is in the ester form
E The lipids are the major component of lens fibre membranes
7 Lens fibres
A Are hexagonal in cross-section
B Attach to the lens capsule
C Have small nuclei
D Interlock with each other
E Have small extracellular spaces
8 Lens metabolism
A Uses glucose from the aqueous and vitreous
B Is predominantly anaerobic
C Is 15% from the pentose shunt
D Has its rate regulated by hexokinase
E Is essential to maintain transparency
9 Cataract
A 90% of people over the age of 65 have some change in lens
transparency
B Includes vacuoles and water clefts
C When mature involves complete disruption of lens chemistry
D Is not produced by viruses
E Is associated with increased lens inositol
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