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Biochemistry > Unit 2 - ECM and Connective Tissues > Flashcards

Unit 2 - ECM and Connective Tissues Flashcards

1
Q

desmoglein and desmocollin

A

desmosomal cadherins, which bind to each other across the extracellular space.

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2
Q

desmosomal proteins bind ot intermediate filaments via

A

plakophilin, plakoglobin, desmoplakin

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3
Q

link the intermediate filaments of adjacent cells into a continuous protein network that provides structural stability, allows the tissue as a whole to withstand tearing or shearing forces.

A

Desmosomes

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4
Q

claudin and occludin.

A

The major proteins present in tight junctions

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5
Q

Anchor epithelial cells (via their actin filaments) to the basal lamina.

A

Focal contacts (focal adhesions)

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6
Q

Anchor epithelial cells (via their intermediate filaments) to the basal lamina.

A

Hemidesmosomes

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7
Q

Integrins

A

the transmembrane protein component of both focal adhesions and hemidesmosomes that provide anchorage for epithelial cells by linking intracellular filament networks.

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8
Q

a large, flexible protein composed of three interwoven polypeptide chains that are held together by disulfide bonds. The head-groups of each polypeptide chain can bind to each other (or to collagen), forming a sheet-like network.

A

Laminin

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9
Q

consists of three protein strands that are loosely packed together. The N- and C-termini of Type IV Collagen molecules can bind to one another (or to laminin), forming a mesh of collagen.

A

Type IV Collagen (non-fibrillar)

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10
Q

a V-shaped molecule consisting of two polypeptides linked by disulfide bonds. Each arm of the V-shaped fibronectin has binding domains for integrins (cell binding), collagen fibers, and proteoglycans. Thus they can serve as adaptor molecules.

A

Fibronectin

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11
Q

Proteins located within the extracellular matrix (ECM):

A

Collagen, Elastin, Proteoglycans, Hyaluronan

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12
Q

provide much of the mechanical strength associated with the extracellular matrix through extensive hydroxylation and cross-linking.

A

collagen fibers

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13
Q

First Step in Fibrillar Collagen Formation

A

Each alpha-chain (monomer) is synthesized as a pro-α-chain polypeptide that is spooled into the lumen of the endoplasmic reticulum during translation.

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14
Q

Second step in Fibrillar Collagen Formation

A

Once fully synthesized in the ER, the immature polypeptide undergoes several types of post-translational modification, hydroxylation of amino acids proline and lysine to form hydroproline and hydroxylysine, as well as glycosylation of selected hydroxylysine residues.

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15
Q

procollagen triple helix

A

Three mature pro-alpha-chains self-assembled after post-translational modification.

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16
Q

tropocollagen

A

Formed by the cleavage of the “loose ends” of each polypeptide procollagen strand after secretion. Nceessary for fibril formation (does not occur in type IV collagen).

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17
Q

fibril

A

formed by the self-assembly of a regularly staggered array of tropocollagen.

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18
Q

driving force for self-assembly of tropocollagen into fibrils:

A

Tropocollagen is 1000x more hydrophobic than procollagen

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19
Q

9 steps of collagen fiber formation.

A
  1. synthesis of pro-a-chain. 2. hydroxylation of selected prolines and lysines. 3. glycosylation of selected hydroxylysines. 4. self-assembly of 3 pro-alpla-chains. 5. procollagen triple-helix formation. 6. secretion. 7. cleavage of propeptides. 8. self assembly into fibrils. 9. Aggregation of fibrils to form collagen fiber.
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20
Q

modifies the proline residues of collagen polypeptides to give rise to the amino acid hydroxyproline.

A

Prolyl hydroxylase

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21
Q

kinked structure of procollagen

A

formed by repeating sequences of glycines, prolines, and hydroxyproline resides. Enables interlocking, conferring stablity to triple helix structure.

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22
Q

Within th ER, catalyzes an oxidative deamination reaction between lysine or hydroxylysine, forming both inter-and intramolecular crosslinks within and between tropocollagen molecules. Vitamin C required.

A

lysyl hydroxylase

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23
Q

Scurvy

A

Diet-related Defect In Collagen Modifications. Prolonged vitamin C deficiency results in a decrease in proline and lysine hydroxylation on newly-made collagen fibers

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24
Q

hydrophobic monomers extensively crosslinked to each other that act like molecular springs, allowing the network to expand or recoil as tension is applied and released.

A

Elastin

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25
Q

glycosaminoglycans bound to core proteins

A

Proteoglycans

26
Q

The components of ground substance

A

Proteoglycans, hyaluronan, and glycoproteins

27
Q

long polysaccharide chains consisting of a series of disaccharide repeats (typically an amino sugar linked to an acidic sugar). Stingguised by their sugars and sulfate groups.

A

Glycosaminoglycans (GAGs)

28
Q

Hyaluronan

A

VERY long (25,000+ repeats), Not covalently bound to proteins (acts as a scaffold), Negatively charged, but not sulfated.

29
Q

one of the GAGs that attaches to hyaluronan, note the series of negative charges that attract Na+, which draws water to the molecule.

A

Heparan sulfate glycosaminoglycan

30
Q

GAG linkage to core protein

A

The serine residues of core proteins are first attached to a tetrasaccharide linker that then attaches to the rest of the GAG chain

31
Q

Multiple proteoglycan molecules non-covalently assembled (with linker proteins) on hyaluronan scaffolds.

A

Proteoglycan aggregate. Due ot stiffness tend to adopt highly extended conformations that occupy a huge volume relative to their mass.

32
Q

Importance of GAGs

A

the gel-like nature of GAGs allows them to cushion tissues against compressive forces. This gel-like matrix is also of great importance in the exchange of nutrients and waste products in tissues which lack vasculature.

33
Q

Clear, gel-like substance of varying density depending on water content that occupies the space between the cells & fibers. Usually lost with histological processing, so appears empty. Composed of Glycosaminoglycans, Proteoglycans and their aggregates, and multiadhesive glycoproteins.

A

Ground substance

34
Q

Repeating, mostly sulfated, disaccharide units.

A

Glyscosaminoglycans (GAGs)

35
Q

Core protein (I) + GAGs (-). Sulfated GAGs give them a high negative charge that attracts Na+ and thus water, forming a hydration shell. Present in ALL CTs, purposeof hydrating ECM.

A

Proteoglycans (PGs)

36
Q

A core component of cartiledge ECM. Individual PG’s indirectly bound to hyaluronan (re-enforced by link protein) creating giant macromolecules that attract large volumes of water, giving ECM gel-like “shock- absorbers”.

A

Proteoglycan Aggregates

37
Q

Charge-based filtration barrier

A

Primary function of GAGs & PGs in BM

38
Q

Most abundant structural component (30% of dry weight of the body). Imparts tensile strength to tissues. Flexible but not elastic.

A

Collagen

39
Q

Fibrillar (I, II, III), Sheet-forming (IV), Anchoring (VII).

A

Collagen types

40
Q

All fibrillar collagens mature to fibril stage, but not all go on to form fibers or fiber bundles. Tropocollagen molecule to fibril to fiber to fiber bundle.

A

Fiber bundle assembly

41
Q

mature collagen molecule

A

Tropocollagen molecule

42
Q

orderly alignment of tropocollagen molecules

A

Fibril

43
Q

localized spot-like adhesions randomly arranged on the lateral sides of plasma membranes. help to resist shearing forces and are found in simple and stratified squamous epithelium. ‘velcro dots’

A

desmosome

44
Q

interact with desmosomes (cell-cell adhesion) and hemidesmosomes (cell-matrix adhesion) via adapter proteins.

A

Intermediate filaments

45
Q

integrin used as adhesive moleculelinking basal lamina to cytoskeleton.

A

Cell-Matrix Junctions

46
Q

small stud- or rivet-like structures on the inner basal surface of keratinocytes in the epidermis of skin that attach one cell to the extracellular matrix.

A

hemidesmosomes

47
Q

types of large macromolecular assemblies through which both mechanical force and regulatory signals are transmitted that serve as the mechanical linkages to the ECM, at sites of integrin binding and clustering.

A

focal adhesions

48
Q

a belt like intercellular junction located between adjacent lateral domains immediately “above” the adherens junction. No CAMs, connected by transmembrane proteins. Help define functional domains (apical-basolateral) - establishing polarity and limit paracellular transport.

A

tight junction

49
Q

Weave back and forth through each cell’s plasma membrane several times

A

transmembrane proteins

50
Q

No CAMs, have transmembrane connexons. Aid in cell-cell communication.

A

Gap junctions

51
Q

is an assembly of six proteins that can be a part of a gap junction channel between the cytoplasm of two adjacent cells. Two come together to complete intercellular gap junction channel.

A

connexon

52
Q

Exchange of small solutes, ions, and water to/from lumen and CT by pasing netween lateral domains. Passive provess.

A

Paracellular transport

53
Q

Transcellular transport

A

Transcellular transportExchange of substances to/from lumen and CT by passing through an epithelial cell. Active process.

54
Q

tight junction, barrier to paracellular transport.

A

Zonula Occuldens

55
Q

occludin and claudins that weave through each cell’s plasma membrane and extend into ICS.

A

Transmembrane proteins

56
Q

rows of transmembrane proteins from adjacent cells that appear as ridges or stitches that act as a barrier to paracellular transport pathway.

A

Junctional strands

57
Q

Hemidesmosomes, Focal Adhesions

A

Cell-to-Matrix Adherents

58
Q

Integrin proteins attached to Basal lamina outside cell and attachment plaque inside cell. Keratin intermediate filaments strengthen them by adhering to attachment plaque. Resists abrasion, sheering, and tearing forces between Epithelial Cells and Basal Lamina. Strong attachment between epithelial cell and basal lamina.

A

Hemidesmosomes

59
Q

Integrin proteins linked to basal lamina outside cell and Actin Filaments inside cell. Aids in adhesion and mechanosensitivity.

A

Focal Adhesion

60
Q

Exchange of small solutes, ions, and water between lumen and connective tissue between the lateral domains. Also allows movement of White blood cells into the Connective tissue

A

Paracellular Transport

61
Q

Claudins join in the intercellular space to form Junctional Strands

A

Occludin and Claudins

Biochemistry (12 decks)

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