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Anatomy and Biochemisty > Exam 1 Koh- Cornea Biochem 1 > Flashcards

Exam 1 Koh- Cornea Biochem 1 Flashcards

1
Q

3 properties of the cornea?

A

Light transmission (transparency), protection and reparation, refractive surface

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2
Q

Cornea is composed of what 2 things?

A

Collagen and GAGs

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3
Q

Epithelium is ___% of total thickness

A

10

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4
Q

The epithelium absorbs ____ wavelength UV protection

A

Short

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5
Q

What are keratins?

A

A family of fibrous structural proteins, tough and insoluble.

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6
Q

What are some forms of keratins?

A

Hair, horns, nails, scales, shells

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7
Q

Glycocalyx

A

Filamentous material coast apical projections

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8
Q

Mucin glycoproteins

A

Promote tear spread and stability

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9
Q

What are sources of O2 for the open eye?

A

Atmosphere, tear film

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10
Q

What are sources of O2 for the closed eye?

A

Palpebral conj, tear film

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11
Q

What are sources of O2 with contact lenses?

A

Tear film, through the lens

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12
Q

What is the uptake of O2 from the epithelium?

A

Tear film, air

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13
Q

What is the uptake of O2 for the endothelium and posterior stroma?

A

From circulation via aqueous humor

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14
Q

What is the primary corneal metabolic substrate?

A

Glucose

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15
Q

What produces 10% of the glucose?

A

Preocular tear film and limbal

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16
Q

How is glucose used in the epithelium?

A

Passive diffusion to stroma

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17
Q

How is glucose used in the stroma?

A

Aqueous humor by carrier-mediated transport via endothelium

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18
Q

The endothelium makes greater use of ___ ___ than epithelium

A

TCA cycle

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19
Q

In the epithelium and endothelium the ___ _____ breaks down 35-65% of the glucose

A

HMP pathway

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20
Q

Keratocytes metabolize very little glucose via what pathway? And why?

A

PPP Pathway, lack 6-phosphogluconate dehydrogenase

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21
Q

How much PPP for the whole cornea?

A

15%

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22
Q

85% of glycolytic glucose converted to _____

A

Lactate

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23
Q

15% of glycolytic glucose converted to _____

A

Pyruvate

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24
Q

The endothelial ATP pump is ____ times as active as the epithelium

A

5

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25
Q

What is the most common type of ATP production between corneal epithelium and endothelium?

A

Anaerobic

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26
Q

Epithelium uses more ____ and endothelium uses more ____

A

PPP, Aerobic

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27
Q

What are the sources of glucose?

A

Tear film, limbal blood vessels, and aqueous

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28
Q

What percentage of glucose from the aqueous?

A

90

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29
Q

Where is Bowman’s layer?

A

Posterior to the epithelial basal lamina

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30
Q

What are the cellular components of Bowman’s layer?

A

Type I and V collagen and glycoproteins

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31
Q

What is Bowman’s layer secreted by?

A

Anterior stromal keratocytes and epithelium

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32
Q

What happens when there is damage to Bowman’s layer?

A

Scarring

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33
Q

What are the cellular components of the basal lamina?

A

Collagen types IV, VII, IX and XVI, fibronectin, heparan sulfate

34
Q

What types of proteoglycans are in the stroma?

A

Keratan sulfate, dermatan sulfate, chondroitan sulfate

35
Q

What types of collagen are in the stroma?

A

Types I and VI (major) and types III and V (minor)

36
Q

What are the cellular components of Descemet’s membrane?

A

Collagen- types IV and VIII, laminin fibronectin

37
Q

What is the most abundant protein in the body?

A

Collagen

38
Q

What is type I tissue in?

A

Skin, bone, tendon, BV, cornea

39
Q

What is type II tissue in?

A

Cartilage, intervertebral disk, vitreous body

40
Q

What is type III tissue in?

A

Blood vessels, fetal skin

41
Q

What is type IV tissue in?

A

Basement membrane

42
Q

What is type VII tissue in?

A

Beneath stratified squamous epithelia

43
Q

What is type IV tissue in?

A

Cartilage

44
Q

What are the fibril forming collagens?

A

I, II, III

45
Q

What are the network-forming collagens?

A

IV, VII

46
Q

What are the fibril-associated collagens?

A

IX

47
Q

Which collagens have a rope-like structure?

A

Fibrillar collagens

48
Q

Which collagens form a 3D mesh?

A

Network forming collagens

49
Q

Collagen is rich in ____ and ____ important in the formation of the triple-stranded helix

A

Proline and glycine

50
Q

What is hydroxylation?

A

Maximizes interchain H bonds and stabilizes the triple helix

51
Q

The polypeptide precursors of the collagen molecule are formed in ______ and are secreted into ____ ____

A

Fibroblasts, extracellular matrix

52
Q

What is the breakdown of collagen fibrils dependent on?

A

Proteolytic action of collagenases, which are a part of a large family of matrix metalloproteinases

53
Q

Normal collagens are highly ____ molecules

A

Stable

54
Q

Osteogenesis Imperfecta

A

Brittle bone syndrome, this disease is a consequence of decreased production of alpha 1 and alpha 2 chains

55
Q

The stroma is what percentage of the corneal thickness?

A

90

56
Q

How many layers of lamallae are in the stroma?

A

200

57
Q

Lamellae

A

Collagen fibrils enmeshed in a matrix (proteoglycans, proteins, and glycoproteins)

58
Q

What types of collagen are in the stroma?

A

I, V, VI, VII, XII, XIV, III

59
Q

What type of collagen is associated with stromal wound healing?

A

III

60
Q

What is the most abundant heteropolysaccarides in the body?

A

GAGs

61
Q

Where are GAGs located?

A

Primarily on the surface of cells or in the ECM

62
Q

What are the functions of GAGs?

A

High viscosity, low compressibility, rigidity provides structural integrity to cells (migration), negatively charged (hydration)

63
Q

Because of their large number of negative charges, these heteropolysaccharide chains tend to be _____ in solution

A

Extended

64
Q

What is the most abundant GAG in the body?

A

Chondroitin and 4 and 6 sulfates

65
Q

Where is chondroitin and 4 and 6 sulfates found?

A

Cartilage, tendons, ligaments, and aorta

66
Q

What do chondroitin and 4 and 6 sulfates form?

A

Proteoglycan aggregates often aggregating noncovalently with hyaluronic acid

67
Q

What does chondriotin and 4 and 6 sulfates do in cartilage?

A

Bind collagen and hold fibers in a tight, strong network

68
Q

What are the most heterogenous gylcosaminoglycans?

A

Keratan sulfates I and II

69
Q

Where is keratan sulfate II found?

A

In loose CT proteoglycan aggregates with chondroitan sulfate

70
Q

Where is Keratan sulfate I found?

A

In cornea

71
Q

What is the only GAG not limited to animal tissue but also found in bacteria?

A

Hyaluronic acid

72
Q

What is hyaluronic acid serve as?

A

Lubricant and shock absorber

73
Q

Where is hyaluronic acid found?

A

Synovial fluid of joints, vitreous humor of the eye, the umbilical cord, loose CT and cartilage

74
Q

Where is dermatan sulfate found?

A

Skin, blood vessels, and heart valves

75
Q

Alpha linkage joins what?

A

Sugars

76
Q

Unlike other GAGs that are ________ compounds, heparin is an ________ component of mast cells that line arteries especially in the liver, lungs and skin

A

Extracellular, Intracellular

77
Q

What serves as an anticoagulant?

A

Heparin

78
Q

Where are glycosaminoglycans degraded?

A

Lysosomes

79
Q

What are the second most abundant corneal constituents?

A

Proteoglycans

80
Q

What are the 3 major proteoglycans?

A

Lumican, keratocan, mimecan

Anatomy and Biochemisty (15 decks)

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