Animals detecting light

Question 1

For humans what is visible light spectrum?

Answer 1

390-700nm (peak of solar radiation spectrum)

Question 2

What is the opsin gene family?

Answer 2

Gene family which receptors in animal eyes are based on, has 7 transmembrane helices

Question 3

Why do photoreceptor cells have extensive membrane?

Answer 3

To accomodate as much rhodpsin as possible (the opsin in rods conserved from jellyfish to humans)

Question 4

What type of photoreceptors are vertebrate rods and cones?

Answer 4

ciliary photoreceptors

Question 5

What are the other type and where are they found?

Answer 5

microvillar photoreceptors, found in molluscs, stacks of microvilli form rhabdoms

Question 6

Draw both

Answer 6

see internet – better than notes

Question 7

Draw how retinaldehyde reacts to light

Answer 7

see notes

Question 8

How does rhodopsin achieve amplification of the signal?

Answer 8

see diagram in notes

Question 9

How does adaptation occur?

Answer 9

guanylate cyclase resynthesises cGMP

Question 10

How does invertebrate phototransduction work?

Answer 10

activated rhodopsin acts through different Gprotein, Phospholipase c activated, cation channel opens(called TRP channel), depolarisation

Question 11

What is exciting about opsin?

Answer 11

Can make opsins mechanically (requiring a retinal-based cofactor) which control an ion channel which can be opened or closed, controlled by photoabsorption, can be expressed in neurons where they control neural activity by shining a light on nerve cell –> optogenetics

Question 12

in plants what is difference in light response?

Answer 12

No GCPRs instead direct electron transfer