BIOB10H3 Lecture Notes - Lecture 10: Disaccharide

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17 Jun 2011
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What is the cytoskeleton?
Extensive protein network
Made on free ribosomesin the cytoplasm, no targeting sequence
Three main components:
1.Microtubules
2.Actin
3.Intermediate Filaments
Cytoskeleton -Functions
Scaffold structural support and cell shape
Internal framework organize organelles within a cell
Movement –directs cellular locomotion and movement of materials within the cell
Machinery for cell division
Key to Cystoskeletal Functions:
1)Structure and Support
2)Intracellular transport
3)Contractility
4)Spatial organization
Memorize table 9.1
Actin: Flexible, helical is used more for contractility and mobility
3) Intermediate Filaments
Heterogenous group of proteins, divided into five classes
~ 10 nm in diameter intermediate in size between microtubules and actin(micro
filaments)
50 gene products
Mainly structural support
Types I IV form filaments
Type V (lamins) are present in the inner lining of the nucleus
Monomers have a long a-helical stretch
Fibrous proteins strong, resistant to stretch
Gives cells/cell structures strength
Monomers form homodimers parallel to one another
Dimers come together antiparallel to form tetramers
Tetramers then polymerize into filaments
Both tetramer and IF(intermediate filament) lack polarity/lack direction
Assembly and disassembly are controlled by: phosphorylation and dephosphorylation
Generally for cell strength not used for intracellular transport etc.
Neurofilaments-important for integrity of axons
Laminsinner nuclear membrane cytoskeleton: determines shape
of nuclear envelope
Keratin:
Keratin: main protein of skin cells (keratinocytes)
Skin is made of many layers constantly dividing
Makes huge amounts of keratin
As skin cells are pushed towards surface they undergo apoptosis ; programmed
cell deathwww.notesolution.com
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Cell dies leaves epidermis covered with a dead, waterproof layer of keratin
protein:
Cornified cells
Plasma membrane forms boundary between a cell and its non-living environment
But cells must respond to external stimuli
Interact in specific ways with other cells and extracellular materials
In multicellular animals
Cells interact with extracellular material to form defined tissues.
These interactions are crucial to the formation of epithelial tissue and connective tissue,
which are crucial for various cellular activities
Extracellular Matrix
Everything that surrounds the cells
Made by cells (secreted)
Organized network of extracellular materials
Often has key regulatory role in determining the shape and activities of cells
Extracellular Matrix -Functions
For support of cells/tissues
Site of cell attachment
Signals to cells
Gives cellsidentity
Sends survival signals, signals to migrate etc.
Substrate for cells to migrate over
Extracellular Matrix
Different ECMs have different amounts of proteins depending on function
Amount of water varies
Ex.; blood versus bone
Amount of bound mineral varies
Ex.; bone has Type I Collagen that binds calcium phosphate
Extracellular Matrix Basement Membrane
Basement Membrane = basal lamina, one of the best defined ECMs
Continuous sheet
Surrounds nerve fibers, muscles, and fat cells
Underlies the basal surface of epithelial tissues
Underlies inner endothelial lining of blood vessels
Basement Membrane -Function
Provide mechanical support for attached cells
Generate signals that support cell survival
Serve as substratum for cell migration
Separate adjacent tissues in an organ
Act as a barrier to macromolecules
-Basement membrane oif capillaries prevent passage of proteins out of blood into tissues.
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