Fundamentals-1: membranes and cytoplasm 2
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the 3 major components of the cytoskeleton
Actin filiments- the smallest in size and determine the cells surface shape and necesary for whole cell locamotion
Intermediate filaments- provide mechanical strength and are intermediate size
- microtubules- largest, determine the postition of organelles and direct the intracellular transport
- form cillia and flagella
Explain the function of the cytoskeleton
- Cell shape
- movement of organelles throughout the cell
- provides motility of motile cells
On an electron micrograph how can you tell the difference in the three times of filaments of the cytoskeleton?
The actin microfilaments are the same width as the membrane or bilayer
How are intermediate filaments formed?
They are built layer by layer and intertwined like a rope. Very strong and that is why their major function is mechanical strength.
They are very tough and survive when the cell dies
hair, skin, scales, claws, fur
which part of the cytoskeleton interacts with the desmosomes to link cells together into a solid sheet
They also are able to be stretched and then returned back to the normal
why do doctors always test for the intermdiate filament of a cancer cell
to find out which part of the area it originated from
Each cell has a particular intermediate filament which will tell the doctors where to look for residual cancer cells/tumors if this tumor has metastisied
where are keratins found
both keratinizing and non keratinizing epithelium
where are vimentin found
these intermediate filaments are found in the mesenchymal cells
fibroblasts, chondroblasts, macrophages, endothelial cells, vascular smooth muscle
where is desmin found
striated and smooth muscles except vascular smooth muscles
The gilial fibrillary acidic proteins are found where?
in glial cells
astrocytes- largest of the glial cells
where are neurofilaments found
these IFs are found in neurons
nerve cell body and processes
what kind of Intermediate filament presents in all types of human cells?
they line the inside of the nuclear envelope and add structure to the nucleolus and attach and help assemble chromatin
only cytoskeletal filament that is not cytoplasmic
what two filaments in the cytoskeleton are constantly changing. how?
Actin and microtubules are constantly growing and shortening. These are very dynamic filaments
Which filaments form the mitotic spindle in a mitotically dividing cell
How do the microtubule form so that it can grow and shorten?
alpha-tubulin and beta-tubulin form a dimer and they assemble head to tail in a spiral tube formation
this gives them a + or - end *not talking about charge*
The functions differ at each end
only can grow/shrink and the +end of the microtubule
what are the 3 things microtubules extend from. what part of the microtubules are attached
microtubules can extend from a centrosome, spindle pole, or basal body of cilium
the end of the tubule is caped and the - end of the tubule can insert itself into a cell
in a mitotic cell the centrosome will double forming the mitotic spindle
what is another name for a centrosome? where is the in the cell?
MTOC- microtubule organizing center
located right below the golgi body of the cell
the + ends of the microtubule attach to the peripheral and the chromosomes
a centrosome contains a pair of centrioles
the centrioles lie in an area that is surrounded by a cloud of protein (centrosome) where the - ends of the microtubules are inserted because of the gamma-tubulin that binds and initiated the growth of the MT
what facilitates growth or shrinkage of the microtubule
the GTP binding protein tubulin will bind GTP and add it to the remaining strand of microtubules and facilitate the growth of the tubule
When the GTP is hydrolyzed to GDP this is when it falls of and elicits the shrinkage of microtubules
where is the golgi located in relation to the MT of the cell?
The golgi is found along side the nucleus and on top of the microtubule organizing structure
What are the two kinds of motors that the microtubule use to transport things within the cell
- Dynein- this transports things to the - end of the tubule
- Kinesin- this transports things to the + end of the tubule
The two motors both denesin and kenesin use ATP as their energy source for the movement
What is the name of the organism that uses the cells microtubules to transport itself toward the nucleus of the cell?
Herpes Simplex virus has a protein that is sythesised to look like the MT binding protein which binds to dynien and uses this to transport itself toward the - end of the tubule to get closer to the nucleus faster.
What is cillia? flagella?
Microtubules are attached at basal bodies (acting as centrosomes) and causes fingerlike projections in the membrane
they rotate back and forth to cause movement. Found in the falopian tubes to help the egg get to the uterus and in the lungs to help dust, debree and mucus to get out of the lung
Flagella is basically the same structur as cillia but they are much larger.
Sperm are the only cells that use flagella and they only have one.
How are cilium and flagellum arranged?
- They are arranged in a "9 to 2" array. They have 9 doublets of MTs and two MTs the middle.
- This is the same structure for the basal body except there are just 9 triplets
what do cilium and flagellum have as a source for movement?
They use dynein motor to slide the microtubules back and forth against each
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