32 Questions
What percentage of total proteins in the human body does collagen account for?
30%
What is the typical structure of collagen proteins?
Trimer
What is the repeated sequence of amino acids found in collagen?
Glycine-X-Y
What is the result of collagen cross-linking and deposition during tumorigenesis?
Stiffer ECM, disrupted tissue morphogenesis, and promoted signaling
What is the function of matrix metalloproteinases in wound healing?
Degrading collagen
Which cell types produce matrix metalloproteinases during wound healing?
Fibroblasts, inflammatory cells, chondrocytes, osteoblasts, and osteoclasts
What is the consequence of mutations in collagen genes?
Chondrodysplasia, osteogenesis imperfecta, Alport syndrome, Ehlers-Danlos syndrome, and dystrophic EB
What is the role of proteoglycans in the extracellular matrix?
Cushioning cells and binding extracellular molecules
What are the two main components of all tissues?
Cellular and extracellular components
What is the matrisome?
The ensemble of proteins that compose the ECM and associated proteins that covalently modify the ECM
What is the function of the ECM in tissues?
To fill the spaces between cells and bind cells and tissues together
What is an example of a type of extracellular matrix?
Basal lamina
What is the composition of the ECM in tendons?
High proportion of fibrous proteins
What is the function of glycocalyx?
To act as a polysaccharide rich coat on the plasma membrane
What is the composition of the ECM in bone?
High concentration of calcium phosphate crystals
What is the purpose of proteases secreted by cancer cells?
To digest proteins of the ECM
What is the structure of basal laminae?
Sheetlike and firm
What is the main function of the dermis?
To provide great strength and elasticity
What is the primary function of the basement membrane?
To provide cell attachment
What is a characteristic of ECM in adult organisms?
It exhibits slow turnover
What is the role of the ECM in angiogenesis?
To modulate the formation of new blood vessels
What is the role of the ECM in cell signaling?
It acts as a reservoir for growth factors
What type of matrix needs to form rapidly and in the correct location in response to injury?
Blood clot
Why is the ECM important in the healing of fractures or wounds?
It retains the capacity to respond to changes
What is the single most abundant protein in animal tissues?
Collagen
What is the main function of glycosaminoglycans in the ECM?
To absorb water and resist compression
What is the characteristic of glycosaminoglycans that allows them to attract large amounts of water?
Their negative charge
What is the main function of hyaluronic acid in joints?
To act as a lubricant
What is the characteristic of proteoglycans?
They are composed of sulphated GAGs covalently linked to a polypeptide chain
What is the molecular weight of aggrecan, a major constituent of cartilage?
3 million Da
What is the characteristic of decorin?
It has a molecular weight of 40 kDa
What is the space occupied by a single hyaluronic acid molecule, swollen with water?
10^7 nm^3
Study Notes
Extracellular Matrix (ECM)
- All tissues consist of two components: cellular component and extracellular component
- ECM comprises specialized structures that constitute the ECM
- Molecular components of ECM are secreted and assembled by cells of the tissue
Composition of ECM
- ECM consists of a variety of secreted proteins and polysaccharides
- Proteins and polysaccharides in ECM are associated with the plasma membrane
- Glycocalyx is a polysaccharide-rich coat on the plasma membrane of endothelial cells or the apical membrane of intestinal epithelial cells
Matrix Structural Proteins
- Matrix structural proteins include tough fibrous proteins, adhesion proteins, and proteoglycans
- Tendons contain a high proportion of fibrous proteins, while cartilage contains a high concentration of polysaccharides that form a firm compression-resistant gel
- Bone ECM is hardened by deposition of calcium phosphate crystals
- Sheetlike structure of basal laminae results from a matrix composition that differs from that found in connective tissues
Collagen
- Collagen is the most abundant protein in the extracellular matrix
- Secreted mainly by fibroblasts, it accounts for up to 30% of the total proteins in human bodies
- Collagen comprises a family of 28 genetically distinct proteins
- Principal structural elements of all connective tissues are characterized by the presence of a repeated sequence of three amino acids: a tripeptide (glycine-X-Y)
- All collagens are trimers in which at least some and often most of the protein chains are involved in forming a triple helix
Functions of ECM
- ECM fills the spaces between cells and binds cells and tissues together
- ECM provides structural integrity, mechanical strength, and resilience
- ECM is involved in cell signaling, providing the basis for signals transmitted to cells by adhesion receptors that bind to its components
- ECM acts as a reservoir for growth factors that also bind reversibly to its constituents
Glycosaminoglycans (GAGs) and Proteoglycans
- Glycosaminoglycans (GAGs) are carbohydrate chains that are usually linked to proteins to form proteoglycans
- GAGs are strongly negatively charged and attract cations, which are osmotically active and thus attract large amounts of water
- GAGs absorb water and resist compression, filling large volumes of space and resisting compressive forces
- Hyaluronic acid (HA) is a nonsulphated GAG that is widely distributed in tissues and facilitates cell migration in embryonic development and wound healing
This quiz covers the extracellular matrix (ECM) component of tissues, including its molecular components and functions.
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