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COM - Neuro Test 2 > Biochemistry Of Vision - 4/7 Seidler > Flashcards

Biochemistry Of Vision - 4/7 Seidler Flashcards

1
Q

Rods have ____ sensitivity and ____ spatial resolution?

Cones?

A

High sensitivity, low spatial

Low sensitivity, high spatial

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2
Q

In the dark, Na channels on rods are what?

Describe the cell

What kind of nt release?

A

Na+ channels open

Depolarized

High rate of nt release

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3
Q

In the light what is the state of the Na+ channels on rods?

Describe the cell

Rate of nt release?

A

Closed

Hyperpolarized

Low rate of nt release

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4
Q

The disc membrane is what kind of system?

What is its photo receptor?
G-protein?
Effector protein?

A

GPCR

Rhodopsin
Transducin
Phosphodiesterase

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5
Q

At what wavelength is rhodopsin maximally absorbed?

What cofactor binds to its center?

A

500nm

Retinal

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6
Q

What is important for the absorption of retinal?

A

Proton attend schiff base interaction/linkage

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7
Q

Which Opsin proteins are located on the X chromosome?

What is their associated maximum absorption?

A

Red - 560

Green - 530

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8
Q

What is the absorption maxima for the blue Opsin? What chromosome is it located on?

Rod Opsin?

A

420nm - 7

500nm - 3

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9
Q

What is the molecular explanation for color blindness?

A

Non-homologous recombination

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10
Q

What causes “the perfect storm” for macular degeneration?

A

High O2 flux
High lipid content
UV rays

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11
Q

What are the macular carotenoids (xanthophylls)?

A

Lutein

Zeaxanthin

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12
Q

Beta-Caroten –> Retinol via what enzyme?

Where does this occur?

A

Dioxygenase

Intestinal mucosa

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13
Q

What is Retinol bound to in the body?

A

Retinol Binding Protein (RBP)

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14
Q

How does calcium ion affect guanylate cyclase?

A

Inhibits the activity of the enzyme

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15
Q

After illumination, how to the cone cells recover for activation?

A

Ca ion leaks out of the cell and this stimulates guanylate cyclase, thus restoring the [cGMP] to reopen the cGMP-gated channels

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16
Q

What enzyme deficiency has been shown to lead to retinitis pigmentsum?

A

LRAT and RPE65

17
Q

In the Retinoid cycle, what happens 1st in the rod cell upon exposure to light?

What enzymatic process happens next?

A

11-CIS to all-trans

Reduction of all-trans-retinal to all-trans-Retinol

18
Q

How does all-trans-Retinol leave the rod cell?

Where does it go?

A

iRBP

RPE and translocated to the ER

19
Q

In the RPE what happens to all-trans-Retinol? Via what?

Then converted to what? By what?

A

Esterified to all-trans-retinyl ester by LRAT

11-cis-retinol by RPE65

20
Q

Before it leaves the RPE, what does 11-cis-Retinol get converted to?

What exports it out of the RPE?

A

11-cis-retinal (oxidation)

iRBP

21
Q

What happens to 11-cis-retinal after it has left the RPE?

A

Up taken into the rod cell and covalent attachment (schiff base) to Opsin forming a functional rhodopsin

22
Q

Deficiencies in Vit A may manifest as what?

A

Night blindness
Visual impairment
Xerophthalmia (dry eyes)
Bitot’s spots (keratin in conjunctiva)

23
Q

What upper respiratory problems may occur due to insufficient Vit A?

A

Bronchitis

Pneumonia

24
Q

Excess Vit A causes what?

A

Liver toxicity

Joint pain

25
Q

Infants exposed to isoretinoin in the womb have what birth defects?

A

Cleft palate

Heart abnormalities

26
Q

Acute promyelocytic leukemia (APL) is what kind of cancer? Characterized by what?

What causes it?

What treats it?

A

Blood and bone marrow marked by buildup of immature WBCs

Fusion of PML Gene and RARalpha gene

All-trans-Retinoic acid via stopping the repression of transcription and cell differentiation can occur

27
Q

Describe the pathway of the processing of visual signals

Where does information from ganglion cells go?

A

Photoreceptors -> interneurons -> ganglion cells

Output to the retina

COM - Neuro Test 2 (11 decks)

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