Eye Flashcards
LEARN HOW TO LABEL DIAGRAM
What’s the retina
Area within the eye that detects light and contains two types of photoreceptor cells
What are the two types of photoreceptor cells in the retina
Rods and cones
What do rods and cones do
Rods-function I’m dim light but do not allow colour perception
Cones- responsible for colour vision and only function in bright light
How are the photoreceptors formed in the eye
The Light sensitive molecule retinal is combined with a membrane protein opsin to form the photoreceptos
In rod cells what is the retinal opsin complex called
Rhodopsin
What does retinal and rhodopsin do
Absorbs a photon of light and rhodopsin changed conformation to photoexcited rhodopsin
What amplifies a signal
A cascade of proteins
What does photoexcited rhodopsin do
Activates a G-proteins called transducin which activates the enzyme phosphodiesterase (PDE)
How many G-proteins does a single photoexcited rhodopsin activate
Hundreds
What does each activated G-protein activate
One molecule of PDE
What does PDE do
Catalyses the hydrolysis of a molecule called cyclic GMP (cGMP)
What does each active PDE molecule break down
Thousands of cGMP molecules per second
What effects the ion concentration in the membrane of rod cells
The reduction of cGMP concentration as a result of its hydrolysis
What happens when ion channels in the membrane of rod cells close
Triggers nerve impulses in neurons in the retina
