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Biochem > Connective Tissue > Flashcards

Connective Tissue Flashcards

1
Q

Proteoglycans

A

Core protein is covalently attached to multiple, long/linear chains of glycosaminoglycans

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2
Q

Where are proteoglycans found?

A

Synovial fluid, arterial walls, bone/cartilage, ocular virtuous humor, and is a major component of the extra cellular matrix

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3
Q

Functions of proteoglycans

A

Molecular sieves (due to largeness), give some flexibility to substances

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4
Q

Glycosaminoglycans

A

Repeating disaccharide units found on proteoglycans Usually contain a hexosamine and uronic acid

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5
Q

How do the types of glycosaminoglycans differ?

A

Monosaccharides in repeating units change

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6
Q

Which glycosaminoglycan does not link covalently?

A

Hyaluronic acid

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7
Q

What proteins to 5 of 7 glycosaminoglycans covalently link to?

A

Serine and Threonine

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8
Q

Which amino acid does keratan sulfate I attach to?

A

Asparagine

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9
Q

How does hyaluronic acid associate with proteins?

A

Noncovalent linkage

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10
Q

Synthesis of proteoglycans

A
  1. Sugar attaches to serine/threonine
  2. UPD-sugar glycosyltransferases transfer monosaccharides from nucleotide-linked sugar to receptor
  3. 2 glycosyltransferases alt adding monosac.
  4. Sulfate groups added after sugars by PAPS
  5. Secreted and forms into ECM
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11
Q

Proteoglycan aggregate

A

Formed by noncovalent interactions b/t the core protein and hyaluronic acid

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12
Q

Glycoproteins

A
  • Usually shorter carb chains than proteoglycans
  • Carb portion is usually branched and not made of repeating disaccharides
  • Make up most of the proteins circulating in the blood
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13
Q

Glycoprotein synthesis

A
  1. Carb monomers are added to protein (lumen of ER/Golgi)
  2. sugar added via O-linkage (ser, thr) or N-linkage (asn)
  3. Carb side chain extended by sequential addition of sugar residues to nonreducing end
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14
Q

O-Linked Glycosides

A
  • Begin w/ N-acetyl-galactosamine to specific ser or thr side chain on protein
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15
Q

N-linked Glycosides

A
  • Lipid-linked oligosaccharide is contracted (dolichaol molecules on the membrane)
  • sugars added to dolichol by membrane bound glycosyltransferases
  • Oligosaccharides transferred from dolichol to asn by protein-oligosaccharide transferase in ER
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16
Q

Degredation of proteoglycans and glycoproteins

A
  • Lysosomes endocytose the molecules
  • Glycosidases degrade carb portion of molecules
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17
Q

Endoglycosidase

A

Cleaves the carb chain to shorter oligosaccharides

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18
Q

Exoglycosidase

A

Removes sugar residue from the nonreducing end

19
Q

Collagen Structure

A
  • Triple helix made of 3 alpha chain, left handed helices (3 residues per turn)
  • Chains wound together (right handed) and H-bonds stabilize
  • Glycine-X-Y is repeated pattern
20
Q

Proline and hydroxyproline: role in collagen helices

A

Increases rigidity in collagen helices

21
Q

Synthesis of Collagen

A
  1. Preprocollagen synth. (has a signal sequence and polypeptide extension removed from N&C terminals)
  2. triple helix formed from C-terminal bc had the ability to form both inter- and intrachain disulfide bonds
22
Q

Propel hydoxylase

A
  • Hydroxylates the proline molecules, making necessary hydroxyproline
  • Vitamin C and α-ketoglutarate are cofactors
23
Q

Lysine/hydroxylysine

A
  • Formed via Lysyl hydroxylase
  • Either lysine or hydrated form can be in Y position
24
Q

Interruptions

A
  • Areas of globular structures interspersed in the triple helical structure
  • Lack Gly-X-Y form
  • Ex: Collagen IV
25
Q

Type I and V of collagen

A

Skin, bone, tendon, blood vessels, cornea

26
Q

Type II of Collagen

A

Cartilage, intervertebral disks, nitrous body

27
Q

Type III of Collagen

A

Blood vessels, fetal skin

28
Q

Type IV of Collagen

A

Basement membrane

29
Q

Ehlers-Dalos Syndrome

A
  • Inheritied genetic disorder affecting collagen
  • Signs: hyperflexibility of skin, abnormal tissue fragility, increased joint mobility
  • 10 types
30
Q

Type IV of Ehlers-Dalos Syndrome

A

Most serious type that can cause ruptures of the bowl arteries due to abnormalities in type III collagen

31
Q

Type VI of Ehlers-Dalos Syndrome

A

Hysyl hydroxylase deficiency results in joint hypermobility/ocular rupture

32
Q

Type VIIC of Ehlers-Dalos Syndrome

A

Procollagen N-proteinase deficiency results in joint hypermobility (from abnormally thin, irregular collagen fibrils)

33
Q

Alport Syndrome

A
  • x and autosomal linked
  • Affects Type IV collagen fibers
  • Signs: hematuria, can developed ESRD due t orenal basal abnormaility
34
Q

Scurvy

A
  • Vitamin C deficiency that affects collagen production (prolysyl and lysyl hydroxylase cofactor)
  • Signs: bleeding gums, subcutaneous hemorrhages, poor wound healing
35
Q

Elastin

A

Add elastic properties of extensibility and elastic recoil in tissue (stretching without tearing)

36
Q

Synthesis of Elastin

A
  • synthesized in a single tropoelastin molecule
  • No extention peptides in C/N terminals, Gly-X-Y, triple helices, or card portions
37
Q

Lysyl oxidase

A
  • involved with collagen processing
  • Also deanimates lysyl residues from the tropoelastin
38
Q

Desmosines

A
  • Major cross-link of elastin (CL is unique to elastin)
  • 3 lysine-derived aldehydes w/ an unmodified lysine
  • CL makes it highly insoluable and extremely stable
39
Q

Williams syndrome

A
  • Developmental disorder affecting CNS and connective tissue
  • 90% of subjects have elastin deletion – Probable cause of aortic stenosis found in condition
40
Q

Fibrillin

A
  • Large glycoprotein that is a structural component of microfibirls
  • Secreted into the ECM to be incorporated into insoluable microfibrils
  • Provides a scaffold for deposition of elastion
41
Q

Marfan Syndrome

A
  • Autosomal dominant – affects connective tissue
  • Signs: Tall, long digits, hyperflexibility of joints, cardiovascular problems
  • Fibrillin gene is deleted/missense mutations
42
Q

Fibronectin

A
  • Soluble glycoprotein found in large amounts in the ECM
  • Dimmer joined by disulfide bonds near C-terminal
  • Arg-Gly-Asp sequence (RGD) that binds to integrin
  • 7 binding sites doe heparin, fibrin, collagen, DNA, cell surface proteins
43
Q

Laminin

A
  • 3 distinct polypeptide chains linked together to form elongated cruciform shape
  • Binding site for Collagen IV, heparin, integrin
  • Primary component of basal lamina
44
Q

Basal lamina components

A

Laminin, enactin, type IV collagen

Biochem (24 decks)

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