The Eye

Question 1

what is Retinal

Answer 1

LIGHT SENSITIVE molecule

Question 2

what is Opsin

Answer 2

MEMBRANE protein

Question 3

Retinal + opsin

Answer 3

RHODOPSIN

Question 4

how does Retinal work?

Answer 4

absorbs a photon of light causing rhodopsin to become photoexcited rhodopsin

Question 5

What does Rhodopsin Do?

Answer 5

activates G-Protein transducin. This activates the enzyme PDE (phosphodiesterase).

Question 6

ROD CELLS

Answer 6

more sensitive at low light intensities because of a high degree of amplification. = ONE PHOTON of light stimulates hundreds of G-protein which stimulates many enzymes!

Question 7

how does PDE (Phosphodiesterase) work?

Answer 7

catalyses the hydrolysis of cyclic GMP (cGMP). PDE breaks down thousands of cGMP. This reduction in concentration of cGMP causes the ion channel to close. This triggers a nerve impulse.

Question 8

Cone Cells

Answer 8

different forms of opsin, each has a specific wavelength of colour. Red, Green or blue. UV light in other animals (birds)