Retinal Biochemistry

Question 1

What are the 4 major functions of the retina?

Answer 1

Phototransduction, Light and Dark Adaptation, Separation of Signals, Initial info processor

Question 2

This nuclei of the brain aids in visual perception

Answer 2

Lateral Geniculate Nucleus

Question 3

This nuclei of the brain aids in pupillary reflex

Answer 3

Pretectal Area of Midbrain

Question 4

This nuclei of the brain aids in eye movement

Answer 4

Superior colliculus

Question 5

This nuclei of the brain aids in control of diurnal rhythms and hormonal changes

Answer 5

Suprachiasmatic Nucleus of the Hypothalamus

Question 6

Mueller cells provide _____ and _____ support to the neurons of the sensory retina

Answer 6

Structural and Metabolic

Question 7

Mueller cells regulate the extracellular space by _______ off potassium into the vitreous, blood and subretinal space.

Answer 7

Siphoning

Question 8

Potassium is increased during _____ activity.

Answer 8

Neuronal

Question 9

What are the functions of the RPE?

Answer 9

• Synthesize Extracellular Materials
• Phagocytosis of OS discs
• Contain hydrolyzing enzymes to digest discs
• Absorption of scattered light

Question 10

What material is synthesized from the apical portion of RPE?

Answer 10

Proteoglycans

Question 11

What material is synthesized from the basal portion of the RPE?

Answer 11

Bruch’s Membrane

Question 12

What cell in the RPE absorbs scattered light not captured by the photoreceptors?

Answer 12

Melanosomes

Question 13

By absorbing scattered light, the RPE protects the eye from ___ _____ damage.

Answer 13

free radical damage

Question 14

The outer segment of photoreceptors are specialized for ____.

Answer 14

photoreception

Question 15

How does the outer segment detect light?

Answer 15

A photon is absorbed by visual pigment molecules on the outer segment discs

Question 16

How does the phototransduction cascade work?

Answer 16

Light is converted into an electrical signal, which changes the membrane potential

Question 17

What are the 2 main proteins found in OS discs?

Answer 17

Peripherin and Rom-1

Question 18

What is the function of Peripherin and Rom-1?

Answer 18

To regulate disc membrane fusion events in disc morphogenesis

Question 19

What is the main visual pigment protein found in OS discs to help detect light? this aids in what pathway?

Answer 19

Opsin, 80% of OS protein

Phototransduction

Question 20

What’s the significance of have polyunsaturated fatty acids in the rod OS?

Answer 20

• aids in the fluidity of the disc membrane

Question 21

What’s the major fatty acid found in retinal rod OS?

Answer 21

DHA

Question 22

What are the 3 characteristics of photoreceptors

Answer 22

Post-mitotic
Terminally Differentiated
Undergo membrane renewal

Question 23

Why do membranes go through membrane renewal?

Answer 23

allows the PR to replace old or damaged outer segment discs

Question 24

In disc morphogenesis, discs are formbed by _______ of the ______ outer segment plasma membrane

Answer 24

evagination, basal

Question 25

Disc shedding occurs as a ____ process.

Answer 25

daily process

Question 26

In rods, onset of light in the morning triggers phagocytosis for how many hours?

Answer 26

1-2 hrs

Question 27

Human OS discs are replaced in how many days?

Answer 27

10

Question 28

Outer Segments of PR are susceptible to oxidative damage due to what 3 things?

Answer 28

High oxygen content, High concentration of PUFAs, Light stimulation (photooxidation)

Question 29

What are the 2 actions of free radicals

Answer 29

Membrane damage and Lipid Peroxidation

Question 30

How does Lipid Peroxidation work?

Answer 30

Free radicals attach to PUFAs and induce a chain rxn that breaks down membranes

Question 31

Name the 5 defense mechanisms to free radical damage.

Answer 31

Absorption of Light, filtration of light, Antioxidants, Enzymes, RPE,

Question 32

what 3 antioxidants can be used as a defense mechanism?

Answer 32

Beta-Carotene, Vitamin C and E

Question 33

What enzymes can be used as a defense mechanism against free radicals?

Answer 33

Superoxide dismutase Glutathione peroxidase Catalase

Question 34

What are the 2 xanthophylls used to help filter light? How?

Answer 34

Lutein and Zeaxanthin Form an optical filter that helps filter damaging blue light

Question 35

Which xanthophyll filters the most blue light?

Answer 35

Lutein

Question 36

What cells help with the absorption of light?

Answer 36

melanosomes

Question 37

What 2 components make up the visual pigment?

Answer 37

Chromophore (11-cis-retinal) and Opsin

Question 38

What is the derivation and structure of Chromophore?

Answer 38

Vitamin A | Aldehyde

Question 39

The RPE acquires Vitamin A from what 3 areas?

Answer 39

Circulation Ingested Discs Any released during phototransduction

Question 40

What is the structure of Opsin?

Answer 40

Glycoprotein, an integral membrane protein

Question 41

How many alpha helices is found in opsin? Which one does chromophore attached to?

Answer 41

7 alpha helices, chromophore is attached to the 7th one

Question 42

Scotopsin is for which photoreceptor?

Answer 42

Rod

Question 43

Photopsin is for what photoreceptor?

Answer 43

Cone