Exam 2 Ch 19 Flashcards
What are the 2 main ways cells are bound together
Cell-Cell junctions and the extracellular matrix
What are the 2 types of Cell-Cell anchoring junctions
Adherens and Desmosomes
What do adherens junctions do
Anchor actin cytoskeleton in cell 1 to the actin cytoskeleton of cell 2
What do desmosomes do
Anchor the intermediate filaments in cell 1 to the intermediate filaments of cell 2
What are the 2 cell-matrix anchoring junctions
Actin-linked cell matrix and Hemidesmosomes
What do Actin-linked cell matrix junctions do
Anchor actin cytoskeleton to the extracellular matrix
What do Hemidesmosomes do
Anchor intermediate filaments the extracellular matrix
What do cell-matrix anchoring junctions do
Anchor the cytoskeleton of a cell to the extracellular matrix
What do Cell-cell anchoring junctions do
anchor the cytoskeleton of one cells to the cytoskeleton of another
What do tight junctions do
Seal cells together
What do gap junctions do
create channels between two cells that allow for the passage of small molecules and electrical signals
What do cadherins do
Link cells together at the cell-cell anchoring junctions
Where do cadherins link cells together.
Adherens junctions and desmsomes
What are cadherins dependent on for maintaining adhesion
Calcium
What kind of binding do cadherins exhibit
Homophilic
What is homophilic binding
Like binds to like
What side are epitheleial cells anchored to other tissue
Basal side
Which side of epithelial cells are free of attachments
Apical
What does it mean that tight junctions serve as a selectively permeable barrier
It separates fluid on one side of the cell from fluid on the other side but allow certain molecules through
What are the transmembrane proteins that form the tight junctions
Claudins and occludins
How do Gap junctions couple the cells
both electrically and metabolically
How do gap junctions work
They create a channel between the 2 cells that allows small water-soluble molecules to pass from one cell to the other but not allowing large molecules to passthrough
What protein forms the channels for the gap junctions
Connexins which come together to form connexons
What is the extracellular matrix made up of and oriented by
The cells within it
What do fibroblast do and where are they found
They create alot of extracellular matrix by secreting the macromolecules
Commonly found in connective tissue
What are the 3 major classes of extracellular matrix macromolecules
GAGs, Fibrous proteins, Glycoproteins
Describe GAGs
Resist compressive forces
Highly negatively charged
Unbranched polysaccharides (repeating disaccharide units)
How are GAGs linked to a protein
Via a link tetra-saccharide on a serine residue of the protein
What are the 2 types of Fibrous proteins
Collagen and elastin
Describe collagens
A major protein in the ECM
Form long, stiff triple alpha helical structures
Organize in bundles
What are collagen fibrils
bundles of collagen
What are collagen fibers
Bundles of collagen fibrils
What type of collagen do NOT aggregate togehter
Fibril-associated collagens
They bind to the surface of fibrils formed by fibrillar collagens instead
Describe elastin
Main component of elastic fibers
Secreted ito extracellular matrix and assembles into elastic fibers
What are the 2 main components of elastin
Hydrophobic segment and Alpha-helical segment
What is the hydrophobic segment of elastin used for
the elastic properties
What is the of elastin Alpha-helical segment used for
cross link to adjacent molecules
describe glycoproteins
Act as a large scaffold with multiple binding sites for other matrix macromolecules
Helps organize the ECM and helps cells attach to it
What is fibronectin
The best understood glycoprotein
Binds to collagen, other proteoglycans, and integrins on cell surface
A dimer with 2 very large subunits joined by a disulfide bond at C term
Describe the basal lamina
Specialized type of ECM
Lies underneath epithelium
HAs many roles
Primarily made up of 2 EMC macromolecules
Roles of Basal lamina
Structural; filtration; determine cell polarity; influence cell metabolism; organize the proteins on adjacent cellular plasma membranes; promote cell survival, proliferation, or differentiation; serve as highways for cell migration
What are the two ECM Macromolecules in the basal lamina
Laminin and Type 4 collagen
Describe Laminin
A glycoprotein composed of 3 long polypeptide chains held together by disulfide bonds
They can self assemble into a network through interactions between their heads
Describe Type 4 Collagen
network forming collagen
Several isoforms that can twist together to form a ropelike superhelix
What do integrins do
Anchor cells to the extracellular matrix
Where do integrins link cells
Hemidesmosomes and Actin-linked matrix junctions
What do hemidesmosomes do
Anchor intermediate filaments to he extracellular matrix
What do actin-linked matrix junctions do
Anchor the actin cytoskeleton of a cell to the extracellular matrix
Describe an inactive integrin
External segments are folded and cannot bind to ECM proteins
Internal segments cannot interact with cytoskeletal linker proteins
Describe active integrins
Conformational change and binding sites are exposed
