Test 3 - Mokrzan Flashcards
Define extracellular matrix
A complex network of macromolecules in the extracellular space
What is the extracellular matrix secreted by?
The cells which inhabit it
What is the role of the extracellular matrix?
Gives structural and organizational support to tissues
T/F: The extracellular matrix makes up a substantial part of tissue volume
True
Collagen makes up ___% of the total body protein?
30%
___% of collagen is type __
90% of collagen is type I
Collagen has what type of structure? How is this structure strengthened?
Collagen has a triple-helical structure, strengthened and stabilized by crosslinks
There are both ____ and ____ collagens
Fibrillar and nonfibrillar
T/F: The same types and combinations of collagen molecules predominate in different tissues
False. Different types and combinations of collagen molecules predominate in different tissues
Collagen is frequently _____, and synthesis is affected by physiological conditions such as ___ or ___ ____
Remodeled
Diet
Mechanical Stress
Osteogenesis/Dentogenesis imperfecta is the result of a genetic mutation that causes:
The glycine in Type I collagen to be replaced by another amino acid
What is the role of elastin?
It provides flexibility and resilience to the ECM
What is the predominant ECM molecule in blood vessels?
Elastin
Where is elastin found?
In tissues that require elasticity
How is elastin stabilized?
By two-way crosslinks
When do you stop synthesizing elastin?
After adolescence
What is the role of fibronectin?
Facilitates communication between intracellular and extracellular compartments
T/F: Fibronectin binds to other ECM molesules
True
T/F: Fibronectin binds to integrin molecules on cells
True
What is fibronectin important for?
Cell adhesion, growth, migration, and wound healing
What 2 forms does fibronectin have in order to interact with oral pathogens?
Soluble and insoluble forms
Where is laminin found in?
Primarily in the basal lamina
What is the role of laminin?
Gives structural support to the ECM
Laminin is the major component of:
Basement membranes in epithelial and muscle tissues
Laminin binds to cells, often through what?
The integrin family of proteins
T/F: You can acquire diseases from abnormal laminin
True
What is the function of proteoglycans?
They are the gel-formers of the ECM. They also function in the structure of molecules and diversity.
Proteoglycans have many ____
Negative charges
The negative charges in proteoglycans attract:
Cations and water
The result of proteoglycans attracting cations and water is:
Hydration of the ECM, which provides rigidity and durability
Proteoglycans are < ____% of ECM protein
< 10%
Because of their hydrophilicity, ____ ____ fill most of the extracellular space
GAG chains
Proteoglycans combine to form
Aggrecan
Proteoglycans can also:
- Bind growth factors
2. Regulate enzyme activity 3. Act as co-receptors
What type of diseases are related to proteoglycans?
Lysosomal storage diseases
Define cell junctions
Specialized regions where cells are attached to each other and the ECM
What type of tissues are particularly rich in cellular junctions?
Epithelial tissues
What are tight junctions?
Cell-cell junctions found in all epithelia
What is the role of a tight junction?
To severely limit intercellular permeability and maintain cell membrane polarity (different protein components of apical and basolateral membranes)
How are tight junctions formed?
By sealing strands anchored in the membrane
What are tight junctions required for?
For active transport of solutes across the epithelial barrier
All tight junctions are impermeable to:
Macromolecules
T/F: Permeability to small molecules in tight junctions can vary
True
Permeability of small molecules in tight junctions varies depending on:
The number of sealing strands and the different transmembrane proteins (occludin and claudin families) that comprise them
What is the role of an anchoring junction?
To bind cells to each other and to the ECM
Where are anchoring junctions found?
In all tissues, especially those subject to mechanical stress
What are adherens junctions?
Cell-cell junction found primarily in epithelia
Adherens junctions form:
A continuous adhesion belt just below the tight junction
Transmembrane proteins in adherens junctions are
Cadherins
Adherens Junctions connect:
Bundles of actin filaments (contractile)
Adherens junctions are necessary for:
Tight junction formation and epithelial tube formation in morphogenesis
Desmosomes are:
Cell-cell junctions that “rivet” cells together
Where are desmosomes found?
Primarily in epithelia and muscle cells
What do desmosomes contribute to?
Tissue strength and durability
Transmembrane proteins in desmosomes are:
Cadherins
What do hemidesmosomes resemble?
Half-desmosomes
What is the difference in hemidesmosomes and half-desmosomes?
Hemidesmosomes bind cells to the ECM
Transmembrane adhestion proteins in hemidesmosomes are:
Integrins
Hemidesmosomes attach the junctional epithelium to the:
Tooth enamel
Focal adhesions are:
Spot-type junctions that link the cell cytoskeleton to the ECM
Focal adhesions can contain as many as ___ different proteins
100
How are focal adhesions dynamic?
They can form, change, or disappear in response to intracellular or extracellular signals
Focal adhesions transmit external mechanical signals via __ ___
Integrin receptors
Focal Adhesions are important in:
- Cell migration
- Motility
- Differentiation
- Proliferation
- Orthodontic tooth movement
What are gap junctions?
Communicating junctions found in nearly all cells except skeletal muscle and blood cells
What do gap junctions allow for?
Small molecules and electrical charges to pass directly from cell to cell
Channels, called ____, are hexamers of connexin proteins
Connexons
T/F: Connexon permeability varies with the identity and combinations of connexins present
True
Gap junction permeability can be regulated by:
Both intra and extracellular signals
T/F: Gap junctions allow the cells of a given tissue to function together quickly and in a coordinated fashion
True
