Question

Cell Communities:

a. Differentiate between extracellular matrix and cell wall.

b. Identify fibers that lend strength to cell walls versus the extracellular matrix. Relate their structure to their function.

c. Describe collagen organization. What is the role of glycosylation in the extracellular matrix?

d. Explain how cells in epithelial sheets are polarized. What are the names for epithelial tissue based on cell shape and number of cell layers?

Answer 1

a)Extracellular matrices are composed of tough fibrous proteins embedded in a gel-like polysaccharide ground substance—a design basically similar to that of plant cell walls. ... The major structural protein of the extracellular matrix is collagen, which is the single most abundant protein in animal tissues.The extracellular matrix helps cells to bind together and regulates a number of cellular functions, such as adhesion, migration, proliferation, and differentiation. It is formed by macromolecules, locally secreted by resident cells.

  The cell wall is the protective, semi-permeable outer layer of a plant cell. A major function of the cell wall is to give the cell strength and structure, and to filter molecules that pass in and out of the cell. They are found in bacteria, archaea, fungi, plants, and algae. Animals and most other protists have cell membranes without surrounding cell walls.

b)A major component of the extracellular matrix is the protein collagen. Collagen proteins are modified with carbohydrates, and once they're released from the cell, they assemble into long fibers called collagen fibrils.

Collagen plays a key role in giving tissues strength and structural integrity.

  Cellulose. Cellulose is an essential structural component of the primary cell wall of green plants, many forms of algae, and the oomycetes. ... The cellulose chains (20–300) are grouped to form cellulose fibers, which are linked together by hydrogen and van der Waals bonds forming microfibrils.

c) Collagens are the most abundant protein in the ECM. Collagens are present in the ECM as fibrillar proteins and give structural support to resident cells. Collagen is exocytosed in precursor form (procollagen), which is then cleaved by procollagen proteases to allow extracellular assembly.

  Glycosylation of extracellular matrix (ECM) proteins. More than 90% of ECM proteins are glycosylated, which can affect protein identification with antibodies. ... Removal of glycosaminoglycans (GAGs) and small oligosaccharides or removal of GAGs alone affects protein migration by gel electrophoresis.

d)Epithelial cells become polarized along the apical-basal axis. ... These include regulating the vectorial transport of ions across cell sheets during their barrier function as well as ensuring directionality during their secretory and absorptive functions .