Lecture 22: Phototransduction Flashcards

1
Q

What opsin is found in rods?

A

Rhodopsin

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2
Q

Rods have ____ sensitivity and ____ spatial resolution.

A

Rods have high sensitivity and low spatial resolution.

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3
Q

What opsins are found in cones?

A

Three opsins: red, green, and blue

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4
Q

Cones have ____ sensitivity and ____ spatial resolution.

A

Cones have low sensitivity and high spatial resolution.

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5
Q

What portion of the photoreceptor is connected to the bipolar cell?

A

Inner Segment

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6
Q

What is included in the GPCR system of the outer segment of photoreceptor cells?

A

Opsins
Transducin
cGMP phosphodiesterase

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7
Q

What is included on the surface membrane of the outer segment of photoreceptor cells?

A

cGMP gated Sodium Channels
Sodium/Calcium exchanger
Guanylate cyclase

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8
Q

What happens to cGMP gated Sodium Channels in the dark?

A

They are open and cells are depolarized

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9
Q

What happens to cGMP gated Sodium Channels in the light?

A

They are closed and cells are hyperpolarized

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10
Q

What AA is found in the center of the 7TM receptor?

A

Lysine-296

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11
Q

What is the difference between the Schiff base and protonated Schiff base of Retinal bound rhodopsin?

A

Protonated Schiff base absorbs >440 nm

-active player for signal transduction

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12
Q

What happens when photon when light contacts 11-cis retinal?

A

11-trans-retinal, kicking off the entire signal transduction pathway

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13
Q

What is the inheritance pattern of colorblindness?

A

X-linked

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14
Q

Gt activation by light activates what?

A

cGMP Phosphodiesterase

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15
Q

What happens when there is low cGMP?

A

Hyperpolarization of visual cells –> visual signal transduction

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16
Q

What can cause signal termination?

A
  1. Rhodopsin Kinase
  2. Rapid hydrolysis of ATP to ADP
  3. Elevated levels of cGMP
17
Q

What are consequences of Vitamin A deficiency?

A
Night blindness
Xerophthalmia
Keratinization of epithelium
Dry, scaly skin
AMD
Blindness in children
Cornea issues
Increased likelihood of dying from infections
18
Q

What are bitot spots?

A

Build up of keratin in conjunctiva (looks foamy)

19
Q

What is xerophthalmia

A

Abnormal dryness of conjunctiva and cornea of the eye with inflammation and ridge formation

20
Q

What are the two cellular systems of the retinoid cycle?

A
Photoreceptors
Pigmented Epithelium (RPE)
21
Q

What are two important proteins in the retinoid cycle?

A

LRAT

RPE65

22
Q

What is macular degeneration?

A

Degeneration of RPE and retina that can result in vision loss