Cytoskeleton and inclusions Flashcards
What ARE THE THREE MAIN TYPS OF PROTEIN FILAMENTS?
-actin filaments
-intermediate filaments
-microtubules
What are actin filaments? And what are their characteristics?
-Thinnest component of cytoskeleton (MOST FLEXIBLE)
-Made of globular actin monomers
* Each with ATP binding site that CAUSES IT TO
- Polymerize into a microfilament (6-8 nm)
* Two strings of beads twisted together
* Monomers oriented in one direction producing polarity
* “Plus end”- growing endand a “minus” end- RARELY GROWS but can happen
-Dynamic structures
* “Plus” end is growing
–As ADP appears through hydrolysis DYNAMIC INSTABILITY occurs (molecules dissociate from minus end)
What are microtubules?and what are its characteristics?
- Hollow non branching cylinders (BIGGER and LESS flexible then actin filaments)
-Heterodimer (two diff proteins used) made of alternating globular tubules molecules - ALPHA tubulin is located at MINUS end
-BETA tubulin is at PLUS end
*Each beta is bound to GTP
-Each microtubule is made up of 13 parallel prtotofilaments
**PLUS end is GROWING
**MINUS end is NONgrowing
*As GDP appears through hydrolysis DYNAMIC INSTABILITY occurs (molecules dissociate from minus end)
Both actin filaments and microtubules grow from a __________
NUCLEATION site
What is a nucleation site?and where are these located?
-anchoring site for both Actin filaments Microtubules that allows them to start growing
-increases AFFINITY of binding
-Actin: nucleation often at plasma membrane (Actin is all around the cell and helps shape the cells - making them have shapes other than just spheres)
- Microtubules: nucleation often at microtubule organizing centers (MOC) (
What happens when ADP is obtained on the actin filaments (obtained from binding/hydolizing of ATP)?
-Binding affinity DECREASES and acting globules tend to fall of on the end
_____ can stabilize or _____ actin filaments and microtubules
-cytosolic proteins
-destabilize
What are the functions of Cytosolic proteins?
-Stabilize/unstabilize actin filaments and microtubules by:
**preventing binding (plus end) to filaments/tubules
**unraveling cytoskeleton if needed
What are the function of bundling proteins?
Provide stronger and more stable actin structures for ACTIN by:
-PROMOTE nucleation at plasma membrane
-CROSS-LINK actin into parallel arrays
-BUNDLE actin filaments at an ANGLE to produce WEB-LIKE networks
Shape and number of actin
filaments and microtubules is
regulated by ________ by
altering the number of
_______________
-the nucleus
-regulatory proteins
What is the function of Actin filaments?
-Maintains cell shape & anchors membrane proteins
* Can provide either flexible or stable support
-Motility (help move cell by moving the cytoplasm with the help of myosin (motor protein DOES THE ACTUAL MOVEMENT) in muscle cells – causes contractions
* Cellular locomotion of other cells
-Movement of vesicles (they function as a track where a motor protein grabs them and moves them along to get them to other parts of the cell)
- Cytokinesis after completion of mitosis
- Myosin needed for contraction of ring- (to split daughter cells)
-Stability for microvilli
What are microvilli?
-extensions of the cell membrane (fingers) that increase the surface area and therefore the amount of nutrients that are absorbed
-seen in intestine and kidney
-supported by actin filaments that are in the microvilli, held parallel by bundling proteins, and are then attached to the base to of the membrane by actin bundles that are cross-links dint a a web
Myosin produces cellular contraction and movement by sliding ____ in opposite direction to where they are going (or bringing a vesicle)…
but how does it do this???
*MOVING VESICLE: myosin(2) that each have 1-2 heads and a tail use their heads to repeatedly bind and release actin filament in a swinging motion, moving won the filament
***HYDROLYZE ATP IN PROCESS
**MUSCLE CONTRACTIONS: Myosin pulls 2 actin filaments toward each other to facilitate cell movement
* 1 anchored to back of cell
* 1anchored further forward in cell
What roles do Microtubules play in the cell?
-Form the MITOTIC SPINDLE
-the MIDDLE of the CILIA (help move undesired things like pollen out of the body) AND FLAGELLA (in sperm)
* Cytostructural support – anchor organelles (KEEP ORGANELLES in specific places)
* Motor proteins (DYNEIN AND KINESIN) move vesicles along microtubular “railroad tracks”
-Some chemotherapy drugs (e.g. vinblastine) suppress
microtubule dynamics
Why do chemotherapy drugs target microtubules?
-prevents cells ability to go through mitosis (and continue to spread) BUT
-IT IS NOT SELECTIVE—> So other highly mitotic cells are also targeted (EPITHELIAL, WHITE BLOOD CELLS, hair loss- bc actively growing)
How is the movement along microtubules mediated?
-DYNEIN and KINESIN
-Two globular ATP-binding motor heads and a tail
(stalk)
-Move only in one direction along microtubule
* Dyneins move toward minus ends (e.g. toward nucleus)
* Cause cilia to bend by sliding microtubules past each
other
* Kinesins move toward plus ends (e.g. away from
nucleus)
What is the appearance of melatonin one stain, and what is its function?
-H&E: Brown pigment
* Wright (Romanowsky)
stain: often dark green,
green-grey
Melanin in epidermis; H&E
stain
Melanin in melanocyte tumor;
Wright stain
-Protection against UV radiation, heat, and
chemical damage
* Coat and feather coloration
* Ink used by many cephalopods
What is the appearance of lipofuscin (wear and tear pigment) on stain? What is it? and where is it found?
-From oxidative breakdown of mitochondria
and lysosomal digestion
-Common in cells with high metabolic rate
* Liver
* Neurons
* Muscle
-Appearance depends on stain used
* H&E: Brown pigment
* Wright (Romanowsky) stain: dark green
LOCATION helps tell difference between melanin and lipofuscing
What is the appearance of HEMOSIDERIN (wear and tear pigment) on stain? What is it? and where is it found?
-Iron storage , breakdown of RBS
-Usually found in macrophages
* Especially in spleen +/- bone
marrow
Seen in any tissue after hemorrhage
Appearance depends on stain
* Fixed H&E stain: Yellow-brown chunky
pigment
* Cytology smear Wright stain: Blue-green
* Prussian blue stain can be used to stain the iron turquoise
What is the appearance of Glycogen on stain? What is it?
-glucose storage
-NOT stained by H& E (Appears as pale vacuoles)
-Carmin (red) – specific for glycogen
What is the appearance of Lipid on stain? What is it?
-Fat droplets
-Found in
* Adipocytes (fat cells)
* Steroid hormone producing cells
* Some types of glands
- Extracted during processing so
appear as vacuoles
