1.4.4.2 the vertebrate eye

Question 1

what is the retina

Answer 1

the area within the eye that detects light and contains two types of photoreceptor cells

Question 2

what are the two photoreceptor cells in the retina

Answer 2

rods and cones

Question 3

what are rods

Answer 3

these are cells that function in dim light but do not allow colour perception

Question 4

what are cones

Answer 4

these are responsible for colour vision and only function in bright light

Question 5

what are combined to form the photoreceptors of the cell

Answer 5

retinal and opsin

Question 6

what is retinal

Answer 6

light sensitive molecule

Question 7

what is opsin

Answer 7

membrane protein

Question 8

what is the retinal opsin complex called in rod cells

Answer 8

rhodopsin

Question 9

what does retinal absorb

Answer 9

a photon of light

Question 10

how does rhodopsin change conformation

Answer 10

when retinal absorbs a photon of light

Question 11

what is rhodopsin called after conformation

Answer 11

photoexcited rhodopsin

Question 12

what does photoexcited rhodopsin activate

Answer 12

a g protein called transducin

Question 13

what does transducin activate

Answer 13

the enzyme phosphodiesterase

Question 14

what is PDE

Answer 14

phosphodieterase

Question 15

how many molecules of g protein are activated by a single photoexcited rhodopsin

Answer 15

hundreds

Question 16

how is the signal amplified

Answer 16

cascade of proteins

Question 17

what does PDE catalyse

Answer 17

the hydrolysis cyclic GMP

Question 18

how many cGMP molecules are broken down per second by each PDE molecule

Answer 18

thousands

Question 19

what does the reduction of cGMP concentration affect

Answer 19

the function of the ion channels in the membrane of rod cells

Question 20

what does the impact on the function of ion channels in the rod cell membranes result in

Answer 20

the closure of ion channels in the rod cell membrane, which then results in nerve impulses in neurons in the retina

Question 21

what can a high degree of amplification lead to

Answer 21

rod cells being able to respond to low intensities of light

Question 22

is it true that in cone cells different forms of opsin combine with retinal to give different photoreceptor proteins, each with maximal sensitivity to specific wavelengths, red green or blue or UV

Answer 22

yes

Question 23

In cone cells, different forms of opsin combine with retinal to give

Answer 23

different photoreceptor proteins, each with a maximal sensitivity to specific wavelengths