Biology Key Terms - Ch. 8: Cytoskeleton And Ecm

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1. Cyotoskeleton
** and the 6 functions...
** filaments are composed of...

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extensive, dynamic network of protein filaments within the cell that’s essential for
**1. cell shape, 2. cell shape changes, 3. cell motility, 4. internal organization, 5. movement of vesicles inside the cell, and 6. responding to external mechanical changes.
** Filaments are composed of strings of polymerized protein.

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2. Actin (microfilament):
** 2 types and what they are...
** each filament is composed of..
** properties of actin...

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a type of filament found in the cytoskeleton;
** found in 2 forms: filamentous actin (f-actin) is the polymerized form and Globular-actin (g-actin) which are the individual monomers of protein.
** Each filament contains 2 strands of f-actin twisted into a helix.
** Actin is thin, flexible and relatively short.

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3. Actin Treadmilling
** leading edge, why its called that

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losing actin at the - end and gaining actin at the + end (leading edge). When both are occurring at the same rate, the length of the actin filament remains the same. The + end is pushing at the membrane, so it is the leading edge.

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4. Cytochalisin B

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causes depolymerization of actin at the plus end, or cell membrane retraction, allowing for the viewing of treadmilling.

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5. Protein motors
** use __ ____ to move along actin
** moving along actin allows for ___ _____

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actin filaments can be on tracks which protein motors bind to and move along using ATP hydrolysis. These proteins motors are calling myosin. As the protein motors move along actin, it allows for cellular contraction.

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6. Myosin

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the protein motors that can translocate on actin

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7. Sarcomere
** if sacromere gets shorter, what happens to the myofibrils?
** how do they get shorter?

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individual contractile unit of a muscle fiber (myofibrils).
** If sacromere gets shorter, so does myofibrils (the myofilament).
** myosin grabs actin and moves the actin towards the center of the sacromere and the actin filaments slide closer together

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8. Pseudopod
** how does this work?

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formation of pseudopods allow for cells to move by use of actin (cell crawling).
** Pseudopod extends and flow of materials pushes pseudopod.

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9. Cytoplasmic streaming
** example:
** helps to...
** how does this occur?

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the circular flow of cytoplasm around the central vacuole in some plants
** ex: cyclosis
** helps to circulate chloroplasts for maximum photosynthesis efficiency.
** occurs by severed actin transforming the gel-like cytoplasm into fluid, myosin actin interactions help the cytoplams flow into newly liquified region

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10. Microtubule
** composed of..
** consist of...
** compared to actin they are...

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fibers that are hollow rods
** composed of alpha and beta tubulins.
** They consist of 13 protofilaments of alpha and beta tubulins dimers.
** They are fatter, less flexible and longer than actin.

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11. Alpha and Beta tubulins
** important in the formation of ____
** how do they form these?

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dimers of one alpha tubulins and one beta tubulins,
** important in the formation of microtubules.
** These dimers connect spontaneously and form protofilaments of many dimers (with a + end and a – end). 13 protofilaments align in a parallel formation to create a tube (microtubule). These microtubules grow (polymerize) and shrink (depolymerize) as dimers.

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12. Protofilament
** the + end is the ___ tubulin & the - end is the ___ tubulin.
** - end is stuck on the ____ & allowing for ...

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long stand of alpha and beta tublulin dimers.
** Has a plus end with the beta-tubulin and a minus end with the alpha-tubulin.
** - end is stuck on the centrisome, allowing for polymerization and depolymerization to occur only at the + end.

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13. Centrosomes
** what extends from centrosomes?
** what attaches to each microtubule in the centisome?
** what is the filler material inside of the centrosome?

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contains a pair of centrioles (modified microtubules). microtubules form stable tracks that extend from the centrosome.
** Gamma tubulins rings attach to every microtubule in the cell and the filler material inside the centrisome is pericentrioler material.

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14. Dynamic instability
** how does this occur?
** describe how microtubles grow and shrink due to dynamic instability
** what is GTP used for?

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microtubules that do not have a stable attachment to proteins on the plasma membrane can grow and shrink.
** The plus end can be capped by GTP that binds to it, allowing for steady growth. When the GTP cap is removed, the microtubule depolymerizes rapidly.
** GTP is how a cell regulates its microtubules.

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15. Centrioles
** where are they found?

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modified microtubules;
** a pair is found in the center of centrosomes.

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16. Dynein
** from which end of the cell to another?

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movement of protein motors from the + end --> – end. Things move from the plasma membrane to the centrisome along microtubules.

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17. Kinesin
** from which end of the cell to another?

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movement of protein motors from the – end --> + end. Things move from the centrisome to the plasma membrane along microtubules.

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18. Cilia

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numerous microtubules that are surrounded by cytoplasm allow for movement cells and of objects over cells by back and forth movement. They row like oars.
Movement is completely by protein motor dynein.

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19. Flagella

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only one of very few microtubules that move back and forth to move cells in one direction. Movement is completely by protein motor dynein.

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20. Intermediate filaments

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a third type of filament in the cytoskeleton; interlock and form tough, fibrous, ropelike structures. No treadmilling, little known about their dynamics. Unpatterned incorporation.

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21. Extracellular matrix (aka ECM)

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a sugar coat of glycoproteins found between the cells (found outside of the cell membranes). Structures are created intracellularly, excreted and assembled extracellularly.

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22. Collagen
** created in the ....
** makes up __ % of protein in human & __ % in animals
** requires ______ for proper assembly

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major component of the ECM; it is the thickest, strongest fiber between cells and it gives the ECM tensile strength;
** created in the endoplasmic reticulum; makes up 50% of protein in humans and 25% in animals and requires Vitamin C for proper extracellular assembly.

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23. Proteoglycans
** function
**GAGs

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gives the ECM compressive strength; 2 PARTS: the core protein with polysaccharide attachments (GAGs); very negative which attracts water and forms a gel (spongy layer) which allows the cell to compress/squish without damage.

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24. GAGs
**function

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glycosaminoglycans; they attach to proteoglycans in the ECM. Very negative which attracts water and forms a gel (spongy layer) which allows the cell to compress/squish without damage.

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25. Elastin
** function

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gives the cell flexibility; protein that can be pulling and released, breaking hydrogen bonds in the tertiary structure (snaps back like a rubber band when healthy).

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26. Fibronection
** function
** know binding sites

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helps attach the cell to the ECM; adhesive protein which has a 2 BINDING SITES: a binding site for extra cellular membrane proteins and a binding site for receptors on the plasma membrane.

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27. Integrin
** functions

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integral membrane proteins. The link that binds the ECM via fibronectins; also can transmit signals from the external environment to the cell interior.

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28. Intercellular Junction
** allows for 3 things
** involves...

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junctions between cells
** allow cells to stick to each other, interact with each other and communicate with each other.
** Involves the ECM and cytoskeletal filaments (actin or intermediate filaments)

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29. Tight Junction
** characteristics and function

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forms an impermeable barrier between cells, makes cells very close, bound by protein.
** prevents material leakage between the cells and allows for cell polarization

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30. Gap Juction (communicating junction)
** allows for...
** how are channels formed

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allows for channels with cytoplasm for flow of ions and other cytoplasmic consititutes to pass from one cell to another.
** protein rings form in the membrane of each cell and attach to each other to form a channel.

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31. Plasmodesmata
** characteristics
** functions

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a type of gap junction in plants where cell walls and membranes are perforated with channels made of protein. This allows for small solutes, water and some types of protein to freely diffuse from cell to cell.

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32. Anchoring Junction
** attached by ____
** an example is ____

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attaches cells to other cells or to the ECM, by use of intermediate filaments. An example would be desmosomes.

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33. Desmosome

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localized, spot-like adhesions randomly arranged in plasma membranes whose function is cell adhesion and resisting of shearing forces.

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34. Adherens Juntion
** attached by ____
** an example is ____

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holds cells together and holds cells to the ECM similar to anchoring junctions, but involves ACTIN (allows for coordination of cell contraction in early development). An example would be adhesion belts.

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• Photobleaching

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reveals actin treadmilling by making actin fluorescent in certain areas to track these areas movement over time.

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• Actin function (6 functions ):

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1. Maintains cell shape (can bear tension)
2. Cell contraction (muscle)
3. Cell crawling (pseudopod formation)
4. Cytoplasmic streaming (cyclosis)
5. Cellular extensions (microvilli)
6. Formation of the cleavage furrow in mitosis

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• Myofibrils:

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bundles of protein fibers that make up muscle cells; composed of actin and myosin (individual unit is a sarcomere) muscle contraction is these sacromeres getting shorter.

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• Cleavage furrow:

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contractile ring of microfilaments that divide the cell during cell division.

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• 5 functions of microtubules:

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1. Helps maintain cell shape (compression-resistance) so the cell can be squeezed and return to original form
2. Highway for movement of vesicles (vesicles containing neurotransmitters migrate on microtubules)
3. Facilitates movement of whole cells (makes up flagella in protozoans and sperm tails)
4. Facilitates the movement of objects over cells (using cilia)
5. Forms spindle fibers for chromosome movement in mitosis/meiosis

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• 3 types of filaments in the cytoskeleton:

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1. Actin
2. Microtubules
3. Intermediate filaments

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• 3 functions of intermediate filaments:

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1. Helps to maintain cell shape (tension bearing element)
2. Anchors the nucleus and some organelles
3. Forms the nuclear lamina

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• 7 functions of the intracellular matrix (ECM):

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1. A spacer which allows for diffusion of small molecules and migration of immune system cells
2. Provides an increase in tissue strength and elasticity
3. Directs proper cell regeneration
4. Marker for tissue identity (recognition of self, otherwise rejected)
5. Induces tissue differentiation in development
6. Template for cell migration in development
7. Can influence the interior of cells, changes in gene expression

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• 5 components of the ECM

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1. Collagen
2. Proteoglycans
3. Elastin
4. Fibronectin
5. Integrins

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• 5 main types of intercellular junctions:

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1. Tight junctions:
2. Gap (communicating) junctions:
3. Plasmodesmata:
4. Anchoring junctions:
5. Adherens junctions: