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