Exam 1 Koh- Cornea Biochem 1 Flashcards Preview

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Flashcards in Exam 1 Koh- Cornea Biochem 1 Deck (80):
1

3 properties of the cornea?

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

2

Cornea is composed of what 2 things?

Collagen and GAGs

3

Epithelium is ___% of total thickness

10

4

The epithelium absorbs ____ wavelength UV protection

Short

5

What are keratins?

A family of fibrous structural proteins, tough and insoluble.

6

What are some forms of keratins?

Hair, horns, nails, scales, shells

7

Glycocalyx

Filamentous material coast apical projections

8

Mucin glycoproteins

Promote tear spread and stability

9

What are sources of O2 for the open eye?

Atmosphere, tear film

10

What are sources of O2 for the closed eye?

Palpebral conj, tear film

11

What are sources of O2 with contact lenses?

Tear film, through the lens

12

What is the uptake of O2 from the epithelium?

Tear film, air

13

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

From circulation via aqueous humor

14

What is the primary corneal metabolic substrate?

Glucose

15

What produces 10% of the glucose?

Preocular tear film and limbal

16

How is glucose used in the epithelium?

Passive diffusion to stroma

17

How is glucose used in the stroma?

Aqueous humor by carrier-mediated transport via endothelium

18

The endothelium makes greater use of ___ ___ than epithelium

TCA cycle

19

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

HMP pathway

20

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

PPP Pathway, lack 6-phosphogluconate dehydrogenase

21

How much PPP for the whole cornea?

15%

22

85% of glycolytic glucose converted to _____

Lactate

23

15% of glycolytic glucose converted to _____

Pyruvate

24

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

5

25

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

Anaerobic

26

Epithelium uses more ____ and endothelium uses more ____

PPP, Aerobic

27

What are the sources of glucose?

Tear film, limbal blood vessels, and aqueous

28

What percentage of glucose from the aqueous?

90

29

Where is Bowman's layer?

Posterior to the epithelial basal lamina

30

What are the cellular components of Bowman's layer?

Type I and V collagen and glycoproteins

31

What is Bowman's layer secreted by?

Anterior stromal keratocytes and epithelium

32

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

Scarring

33

What are the cellular components of the basal lamina?

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

34

What types of proteoglycans are in the stroma?

Keratan sulfate, dermatan sulfate, chondroitan sulfate

35

What types of collagen are in the stroma?

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

36

What are the cellular components of Descemet's membrane?

Collagen- types IV and VIII, laminin fibronectin

37

What is the most abundant protein in the body?

Collagen

38

What is type I tissue in?

Skin, bone, tendon, BV, cornea

39

What is type II tissue in?

Cartilage, intervertebral disk, vitreous body

40

What is type III tissue in?

Blood vessels, fetal skin

41

What is type IV tissue in?

Basement membrane

42

What is type VII tissue in?

Beneath stratified squamous epithelia

43

What is type IV tissue in?

Cartilage

44

What are the fibril forming collagens?

I, II, III

45

What are the network-forming collagens?

IV, VII

46

What are the fibril-associated collagens?

IX

47

Which collagens have a rope-like structure?

Fibrillar collagens

48

Which collagens form a 3D mesh?

Network forming collagens

49

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

Proline and glycine

50

What is hydroxylation?

Maximizes interchain H bonds and stabilizes the triple helix

51

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

Fibroblasts, extracellular matrix

52

What is the breakdown of collagen fibrils dependent on?

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

53

Normal collagens are highly ____ molecules

Stable

54

Osteogenesis Imperfecta

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

55

The stroma is what percentage of the corneal thickness?

90

56

How many layers of lamallae are in the stroma?

200

57

Lamellae

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

58

What types of collagen are in the stroma?

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

59

What type of collagen is associated with stromal wound healing?

III

60

What is the most abundant heteropolysaccarides in the body?

GAGs

61

Where are GAGs located?

Primarily on the surface of cells or in the ECM

62

What are the functions of GAGs?

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

63

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

Extended

64

What is the most abundant GAG in the body?

Chondroitin and 4 and 6 sulfates

65

Where is chondroitin and 4 and 6 sulfates found?

Cartilage, tendons, ligaments, and aorta

66

What do chondroitin and 4 and 6 sulfates form?

Proteoglycan aggregates often aggregating noncovalently with hyaluronic acid

67

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

Bind collagen and hold fibers in a tight, strong network

68

What are the most heterogenous gylcosaminoglycans?

Keratan sulfates I and II

69

Where is keratan sulfate II found?

In loose CT proteoglycan aggregates with chondroitan sulfate

70

Where is Keratan sulfate I found?

In cornea

71

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

Hyaluronic acid

72

What is hyaluronic acid serve as?

Lubricant and shock absorber

73

Where is hyaluronic acid found?

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

74

Where is dermatan sulfate found?

Skin, blood vessels, and heart valves

75

Alpha linkage joins what?

Sugars

76

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

Extracellular, Intracellular

77

What serves as an anticoagulant?

Heparin

78

Where are glycosaminoglycans degraded?

Lysosomes

79

What are the second most abundant corneal constituents?

Proteoglycans

80

What are the 3 major proteoglycans?

Lumican, keratocan, mimecan