Extracellular Matrix Components and Glycoconjugates

Vocabulary flashcards covering the major components of the extracellular matrix and related glycoconjugates.

Extracellular matrix

Three-dimensional network outside cells that provides structural support, guides cell responses, and helps determine tissue architecture.

Fibroblasts

Cells inside the matrix that produce and organize fibrous proteins and glycoconjugates.

Connective tissue

Tissue rich in extracellular matrix that serves as scaffolding and contributes to tissue diversity.

Fibrous proteins

Structural proteins (e.g., α-keratin, collagen, elastin, fibronectin, laminin) produced by fibroblasts and binding to integrins.

Integrins

Transmembrane receptors that mediate cell–matrix and cell–cell interactions and modulate signaling.

Matrix metalloproteases (MMPs)

Enzymes that remodel the ECM by cleaving matrix proteins; activity is regulated by TIMPs.

TIMPs

Tissue inhibitors of matrix metalloproteases; regulate MMP activity to control ECM remodeling.

α-Keratins

Main components of skin, hair, nails; form a left-handed supertwisted coil from two right-handed helices; rich in hydrophobic residues.

Collagen

Most abundant ECM protein; provides tensile strength; triple helix formed by three left-handed helices; ~1000 aa per chain.

Gly-X-Y motif

Repeating collagen tri-peptide unit where X is often proline and Y is often 4-hydroxyproline; glycine occurs every third residue.

Hydroxyproline

Hydroxylated proline that stabilizes the collagen helix; requires vitamin C for formation.

Hydroxylysine

Hydroxylated lysine involved in glycosylation and covalent cross-links between collagen fibrils.

Allysine

Oxidized lysine residue that forms covalent cross-links in collagen fibrils.

Lysyl oxidase

Enzyme that generates allysine from lysine for cross-linking within collagen.

Procollagen

Soluble collagen precursor formed in the ER; loses signal peptide to become procollagen.

Tropocollagen

Triple-helix collagen segment formed after procollagen processing and secreted to form fibrils.

Type I collagen

Most abundant collagen type in the body; forms fibrils with high tensile strength.

Elastin

Major protein of elastic fibers; enables tissues to return to original shape after stretch.

Tropoelastin

Soluble precursor to elastin; secreted and crosslinked to form elastic fibers.

Fibronectin

Glycoprotein that positions cells and supports migration; secreted as a soluble form and assembles into a fibrous mesh.

Laminin

Heterotrimeric ECM protein (α, β, γ) forming sheet-like networks; main component of basement membranes.

Glycoconjugates

Main ECM components comprising proteoglycans, glycoproteins, and glycolipids; provide structure and signaling.

Proteoglycans

Core protein linked to glycosaminoglycans; high carbohydrate content; resist compression and interact with collagen/fibronectin.

Hyaluronan (hyaluronic acid)

Large glycosaminoglycan that forms proteoglycan aggregates with other proteoglycans.

Keratan sulfate

Glycosaminoglycan found in proteoglycans, especially in cartilage.

Chondroitin sulfate

Glycosaminoglycan commonly found in proteoglycans in cartilage.

Syndecan

Membrane-anchored proteoglycan with transmembrane domain and extracellular GAG chains.

Glypican

Glycosaminoglycan-bearing proteoglycan attached to the membrane via a GPI anchor.

Glycoproteins

Proteins covalently linked to carbohydrates; 1–70% carbohydrate by weight; involved in diverse functions.

O-glycosidic bond

Carbohydrate linkage where the sugar attaches to Ser/Thr via N-acetylgalactosamine.

N-glycosidic bond

Carbohydrate linkage where the sugar attaches to Asn via N-acetylglucosamine.

Glycosylation

Addition of carbohydrate chains to proteins; starts in the ER and continues in the Golgi.

Mucins

Glycoproteins with abundant O-linked oligosaccharides; secreted or membrane-bound; lubricate and protect mucosal surfaces.

Lectins

Proteins that bind carbohydrates with high specificity; involved in cell recognition and adhesion.

Secretins

Family of plasma membrane lectins that aid leukocyte movement through capillary walls.

Glycolipids

Lipids with carbohydrate moieties; include cerebrosides and gangliosides; involved in cell recognition.

Cerebrosides

Ganglioside type with ceramide and a single sugar residue.

Gangliosides

Ceramide attached to an oligosaccharide; diverse in composition and important for cell recognition.

ABO blood groups

Antigenic differences determined by ganglioside glycosylation; A and B have extra sugars; type O lacks them.

Lipopolysaccharides (LPS)

Glycolipid complexes from gram-negative bacteria; lipid A and oligosaccharide chains; potent endotoxins.

Mucopolysaccharidoses

Disorders caused by lysosomal glycosidase deficiencies leading to GAG accumulation and skeletal issues.

Lysosomal glycosidases

Enzymes that degrade glycosaminoglycans and other glycoconjugates in lysosomes.