The Vertebrate Eye Flashcards
What are the two photoreceptor cells in the retina
Rods and Cones
What are rods responsible for
Rods function in dim light but don’t allow colour perception
What are Cones responsible for
Cones are responsible for colour vision and only function in bright light
What are cones responsible for
Cones are responsible for colour vision and only function in bright light
How is a photoreceptor protein formed
When retinal (a light sensitive molecule) combines with an opsin
What is the retinal-opsin complex called
Rhodopsin
How is a photoexcited rhodopsin formed
When retinal absorbs a photon of light —> rhodopsin changes conformation to photoexcited rhodopsin
How is a nerve impulse generated
A cascade of proteins is triggered by photoexcited rhodopsin which will amplify a photon signal —> generate a nerve impulse
What does photoexcited rhodopsin activate
Activates transducent , a G-protein, which then transducent activates the enzyme Phosphodiesterase (PDE)
What does Phosphodiesterase (PDE) do
PDE catalyses the hydrolysis of a molecule called cyclic GMP (cGMP)
What does the hydrolysis of cyclic GMP cause
Causes closure of ion channels in membrane of the rod cells —-> triggers nerve impulse in neutrons to retina
What does a very high degree of amplification result in
Results in rod cells being able to respond to low intensities of light
How are different photoreceptor proteins made in cone cells
When different forms of opsin combine with retinal
After different photoreceptor proteins in cone cells are made, what changes
The change of structure allows each new photoreceptor proteins a maximal sensitivity to specific wavelengths e.g red,blue,green or UV
