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15 Cards in this Set

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How do cells stay in contact with each other?
They use cell-cell junctions
Where do cells most obviously exist?
Cell-cell junctions exist between all cells but most obviously in sheets of epithelial cells
What are the 4 types of junctions
1. Tight junctions
2. Adherens junctions (actin belt)
3. desmosomes
4. gap junction
Of the 4 types of junctions, what do they all use?
cadherins, which are calcium dependent proteins.
What do tight junctions do?
make cell sheets impermeable. They divide the PM into 2 functionally distinct domains. ex. apical and basolateral
What do Adherens junctions do?
They link actin cytoskeleton and provide strength to the cell sheets.
What do Desmosomes do?
links intermediate filaments to cytoskeleton and provide strength to cell sheets.
What do Gap junctions do?
1. Allow diffusion of nucleotides, cAMP, AA, ions, sugars, and proteins.
2. primary purpose is cell-cell communication.
3. when cells die, gap junctions can be closed by Ca2+, because when there is an influx of calcium that comes into the cell when the cell dies, it closes its gap jxns.
What are Gap junctions composed of?
2 connexon, and each connexon is composed of 6 subunits called connexin.
What are the functions of extracellular matrix (ECM)-?
1. space for diffusion of oxygen, nutrients, and growth factors
2. space for cells to migrate
3. increase tissue strength (collagen, elastin, GAG)
4. Template for cell regeneration
5. marker for tissue location (caries molecularly from tissue to tissue)
What does collagen provide strength for?
-25% of total protein in a body
-Assembles into fibrils
-Skin: fibril assembly is random, strength in all directions
-Tendons: fibrils are lined up in one direction
-Cornea: fibrils are thick, non deformable and clear
-Bone: fibrils are like plywood, strong in al direction, calcium is precipitated to provide extra strength.
What does elastin do?
Elastin provides flexibility
ex. Skin (shape retention), Blood vessels (expand and contract), and Lungs (expand and contract).
What are GAGs and proteoglycans?
GAGs are unbranched chains of sugars (~80). GAGs are covalently attached to core proteins to form proteoglycans.
What do GAGs and proteoglycans do?
-Resist compression
-Allow diffusion, nutrients, etc..
-take up lots of space.
What is emphysema?
An enzyme called elastase chews up elastin. So, air sacs can't contract back very well after a breath. This equals a progressive disease from smoking.