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Biochem 4 > Extracellular matrix > Flashcards

Extracellular matrix Flashcards

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1
Q

what are the four components of extracellular matrix? functions?

A
  1. Collagen fibers: give tissue tensile strength
  2. elastic fibers: elasticity
  3. Protoglycans and hyaluronic acid: ground substance
  4. Glycoproteins: glue that holds fibers together
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2
Q

what are the parts of the eye associated with the ECM?

A
  1. Cornea
  2. Sclera
  3. Lens
  4. Vitreous humor
  5. Bruch membrane
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3
Q

what is the most abundant protein in the human body?

A

collagen fibers

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4
Q

alpha chains of collagen are stabilized by what kind of bonds?

A

-interchain hydrogen bonds

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5
Q

what are the three groups collagen is organized into and what is is based on?

A
  • fibril forming
  • network forming
  • fibril associated
  • based on location and function
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6
Q

fibril forming collagen is found where?

A

type 1: skin, bone, cornea, blood vessels

type 2: cartillage, vitreous body

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7
Q

network forming collagen is found where?

A

type 8: corneal andd vascular endothelium

-basement membrane

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8
Q

fibril associated collagen is found where?

A
  • cartialge
  • tendon
  • ligaments
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9
Q

collagen fibers are rich in what? contain what?

A
  • rich in proline and glycine

- contain hydroxyproline and hydroxylysine(formed by post-translational hydroxylation of proline and lysine

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10
Q

what enzymes are needed for hydroxylation of proline and lysine? what reducing agents are needed?

A
  • prolyl hydroxylase and lysyl hydroxylase

- requires O2, Fe2+, and ascorbic acid (VITAMIN C) as reducing agents

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11
Q

hydroxylysine can be additionally altered how?

A

-can be glycisylated with glucose before the formation of the triple helix

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12
Q

Vitamin C is required as a cofactor for what?

A

-hydroxylation of proline and lysine residues in collagen

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13
Q

Vitamin C deficiency causes what problems with collagen?

A
  • lack of hydroxylaed proline and lysine
  • impairment of interchain hydrogen bond formation
  • prevents formation of a stable triple helix and effects proper cross-linking
  • decreases tensile strength
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14
Q

Scurvy

A
  • vitamin C deficiency
  • bruising
  • loose teeth and bleeding gums
  • poor bone development
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15
Q

what enzyme does cross linking?

A

lysyl oxidase

-copper dependent

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16
Q

what happens if you have copper deficiency? copper overload?

A

deficiency: X-linked Menkes disease
overload: Wilson disease

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17
Q

collagenopathies

A

defect in any of the synthetic steps

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18
Q

Menkes syndrome (MNK)

A
  • lack Cu2+ (effects lysyl oxidase)
  • X-linked recessive
  • brittle hair (kinky hair)
  • weak muscles and saggy face
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19
Q

Wilson’s disease

A
  • too much Cu2+ (effects lysyl oxidase)
  • autosomal recessive
  • brain tumors, muscle stiffness, vom
  • Kayser-fleischer rings(brown ring around iris)
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20
Q

Osteogenesis Imperfecta type 1? type 2? common characteristics?

A

-brittle bone
Type 1: less severe, mistaken for child abuse, decreased production of collagen
Type 2: fatal in fetus or childhood, mutation in collagen gene
-common symptoms: bone fractures, blue sclera

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21
Q

Ehlers danlos syndrome

A
  • deffective collagen genes or collagen processing enzymes
  • severity depends on mutation and what collagen type is affected
  • Characteristics: flexible skin, hypermobile joints, possibly blue sclera
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22
Q

elastic fiber composition

A
  • inner core of ELASTIN

- outside covered by FIBRILIN

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23
Q

Elastin stretching ability

A
  • protein

- can be stretched like crazy and recoil back to original shape when relaxed

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24
Q

what enzymes make elastin? how? what is it rich in?

A
  • Lysyl oxidase
  • modifies TROPOELASTIN to form a cross linking and produce elastin
  • rich in proline and lysine, BUT DOES NOT HAVE HYDROYPROLINE AND HYDROXYLYSINE
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25
Marfan syndrome
- mutation: mutation of Fibrillin 1 protein (elastin disorder) - rare dominantly inherited condition - tall, long fingers, LENS DISLOCATION, - weak aorta structure, so patients die in midlife after rupture of dilated aorta
26
what is a postive sign of marfans?
-thumb and pinkie overlap when going about wrist
27
proteoglycans or glycoproteins, which one has more protein and which has more carbs?
- protoglycans has more carbs | - glycoprotein has more protein
28
function of proteoglycans
- produce gel-like matrix - basis of ground substance - flexible support for ECM - help movement of materials through ECM - lubricating properties of mucous
29
what are the three components of proteoglycans?
1. proteogycan monomers(GAGs and a core protein) 2. Hyaluronic acid 3. Link protein
30
glycosaminoglycans (GAGs): type of sugar? type of linkage? location?
- long, unbranched chains with repeating disaccharide unit (acidic sugar-amino sugar)******** - glycosidic linkage - found external to the cytosol (inside organelle or exterior of the cell) - NEGATIVELY CHARGED
31
core protein
- linked by SERINE residue - tons of monomer chains extending off of it - divides into 4 families
32
amino sugars of GAGs
- D glucosamine, D galactosamine - amino group is ACETLYATED to eliminate positive charge - can be SULFATED at carbon 4 and 6 to increase negative charge
33
acidic sugar of GAGs
- D glucuronic acid | - have a carboxyl group that has a negative charge at physiological pH
34
GAGs have a strong negative charge due to what?
-carboxyl groups and sulfate groups
35
what is the cool property GAGs have because of the negative charge?
- they repel eachother and develop hydration spheres - they can slip past each other when compressed and release water - reestablish hydration sphere with decompressed
36
what does the water property of the GAGs contribute to ?
- hydraulic absorption and resilience of synovial fluid and VITREOUS HUMOR OF THE EYE - lubricating effects or mucous and synovial fluid
37
GAGs are divided into 6 classes according to what?
- monomeric composition - type of glycosidic linkage - degree and location of sulfate units
38
Chondroitin 4 and 6 sulfates
- class of GAG - most abundant GAG in the body - found in cartilage, tendons, ligaments, aorta
39
Keratan sulfates I and II
- class of GAG - most heterogeneous GAG because they have additional monosaccharides - I: found in cornea - II: found in loose connective tissue
40
Hyaluronic acid (as a class of GAG)
- NOT COVALENTLY ATTACHED TO PROTEIN - ONLY GAG NOT LIMITED TO ANIMAL TISSUE, ALSO FOUND IN BACTERIA - found in synovial fluid
41
Dermatan sulfate
-found in skin, blood vessels and heart valves
42
Heparin*****
- class of GAG - alpha linkage joins the sugars - ONLY ONE THAT IS INTRACELLULAR - component of mast cells - serve as anticoagulant
43
Heparan sulfate****
- class of GAG - same as heparin, but some glucosamines are acetylated and there are fewer sulfate groups - found in basement membrane (extracellular)
44
what are the three steps of synthesis of a proteoglycan?
1. synthesus of the core protein 2. synthesis of the carbohydrate chain 3. addition of sulfate group
45
synthesis of the core protein
- translated into ER lumen by ribosomes - goes to golgi - glycosylated by glycosyltransferases to make short carbohydrate linkage region
46
synthesis of carbohydrate chain
- sequential addition of alternating acidic and amino sugars - glycosyltransferases
47
addition of sulfate group
-sulfotransfurases transfer sulfate groups to sites on the carbohydrate chain
48
Chondrodystrophy
- defect in sulfation of growing glycosaminoglycan chains - disorders that effect development of skeletal system - autosomal recessive - dwarfism
49
degradation of glycosaminoglycans
- in lysosomes, hydrolytic enzymes degrade them | - requires large number of acid hydrolases for complete digestion
50
deficiency of lysosomal hydrolases results in
mucopolysaccharidoses
51
mucopolysaccharidoses: defect, diagnosis, symptoms
- accumulation of glycosaminoglycans in the lysosomes to result in oligosaccharides in the urine - diagnose by the structure of the oligosaccharides and the levl=el of lysosomal hydrolases - look normal at birth
52
Hurler Syndrome: deficiency, symptoms, treatment
deficiency: alpha-L-iduronidase deficiency -most severe type of MPS -corneal clouding and mental retardation -depostion in coronary artery leads to early death Treatment: bone marrow or cord blood transplant, enzyme replacement
53
Hunter syndrome
- iduranante sulfatase deficiency - X LINKED!!!! - NO CORNEAL CLOUDING - enzyme replacement treatment
54
Sanfilippo syndrome
- four enzymes | - nervous system disorders
55
sly syndrome
- beta glucuronidase deficiency - really rare - CORNEAL CLOUDING - unique abnormal hair growth - no approved treatments
56
Membrane bound glycoprotein function
1. cell surface recognition 2. cell surface antigenicity 3. formation of ECM and mucins
57
non membrane bound glycoproteins
- globular proteins secreted in the plasma | - lysosomal proteins
58
carbohydrate chains of glycoproteins
- really short - no serial repeats - branched - may or may not be negatively charged - variable in amount of composition
59
what are the two kinds of linkage glycoproteins can have between carb and protein?
- N or O-linked glycosidic bond | - can have one or both!
60
N-glycosidic link for glycoproteins
-sugar chain is attached to the amide group of an ASPARAGINE side chain
61
O-glycosidic link for glycoproteins
-sugar chain is attached to the hydroxyl group of SERINE OR THREONINE R group
62
O-linked oligosaccharides
- diverse in sugars and arrangements - linear or branched - found on extracellular glycoproteins or membrane glycoproteins - ones on the surface of RBC help provide ABO blood group determinants
63
what are the two broad classes of N-linked oligosaccharides
1. complex oligosaccharides 2. high-mannose oligosaccharides - both classes have the same core pentasaccharide but complex ones have additional sugars and mannose have mostly mannose
64
N-linkage synthesis
- occurs in the ER | - additional sugars added in golgi
65
O-linked synthesis
-occurs only in the golgi
66
soluble glycoproteins
- glycoproteins are secreted from golgi - packed into vesicles that fuse with the cell membrane - they release their content
67
membrane glycoproteins
- glycoproteins integrated into the ER membrane - pass through the golgi - packaged into vesicles then delivered to the cell membrane
68
how do N linked glycoproteins get recognized?
- they are phosphorylated at specific mannose residues - mannose 6 phosphate receptors in golgi recognize them and bind - then put them into vesicles and lead them to the lysosome
69
I-cell disease
- deficieny in the ability to phosphorylate mannose - cannot be recognized in golgi, so they do not go to lysosomes and just go to the plasma outside the cell - accumulation of lysosomal inclusion bodies - LYSOSOMAL STORAGE DISEASE - early early early death
70
degradation of glycoproteins
- in lysosomes - acid hydrolases (exoenzymes)- remove the specific group in the reverse order of assmebly - break bonds from non reducing end to inside - deficiencies in this lead to accummulation of partialy degraded structures in the lysosomes

Biochem 4 (4 decks)

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