CYTOSKELETON Flashcards
Describe the structure and function of intermediate filaments
Intermediate filaments:
structure: strong and ROPELIKE.
function: strengthen cells against mechanical stress
through DESMOSOMES-anchoring junctions (that allow cell-adhesion).
filaments they also support nuclear envelope.
Explain the process of Dynamic instability in mircotubules
Microtubules are dynamic, as they grow (elongate) and shrink continuously.
They keep extending and shortening
Capping proteins ( microtubule length)
-controlled by GTP HYDROLYSIS.
-GTP associated tubulin- elongates
-GDP associated tubulin-disassembles (shrinks microtubule).
GTP cap seen in elongation of microtubule.
Compare kinesin and Dynein activity
Kinesin and Dynein are motor proteins in microtubules
Kynesin- motor protein moves toward plus end; AWAY from cell body.
Dynein- moves TOWARDS from minus end; towards cell body.
Illustrate the activity of cilia and flagella
Cilia- movement, clearing mucus.
flagella- locomotion/movement of cell
ex: sperm cell
recognize actin filament structure and treadmilling
actin filaments have two ends which aid in treadmilling process: movement of monomers through filament
-which uses ATP hydrolysis.
Actin have treadmilling for Growth.
Actin structure: plus end- growth; minus end- diassembly, which depends on ATP hydrolysis.
Actin are thinner than microtubulesa nd occur in bundles.
Diagram the proteins and actions involved in muscle contraction
tropomyosin, troponin, actin, calcium release and binding. sliding of actin and myosin filaments against each other. This action is triggered by cytosolic increase in calcium. Sarcomeres.
Evaluate the action of various pharmacological agents on cytoskeletal activity.
drugs that affect microtubules
Taxol- bind to microtubules, prevents disassembly
Colchicine- bind free tubulin, prevents polymerization.
drugs that affect actin-
phalloidin- bind/stabilizes filaments
cytochalasin- caps filament plus ends, prevent polymerization
latrunculin- bind actin monomers, prevent polymerization.
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What is a common accessory protein for intermediate filaments?
Plectin- accessory protein
Plectin helps stabilize intermediate filaments
-anchor filaments to microtubules
Defects in plectin causes symptoms of
-epidermolysis bullosa (skin blistering condition), muscular dystrophy (muscle tissues) and neurodegeneration
Describe the kind of intermediate filaments in nuclear lamina and the activity that occurs.
Nuclear lamina- made of Lamins (type of intermediate filament)
- PHOSPHORYLATION regulates filaments (regulate assembly of filaments.
- phosphorylated- destabilizing
- dephosphorylated- reassembly of filaments.
Nuclear envelope has to degrade and reform (hence nuclear lamin does the same.
What kind of pathologies are associated with intermediate filaments.
Pathologies;
Progeria- defects in nuclear lamin, that leads to premature aging
Epidermolysis bullosa- mutation of keratin gene
symptoms: Skin easily blisters and damages.
mutation in plectin protein can cause epidermolysis bullosa as well.
what kind of cells do you see microtubules in?
Microtubules seen in nondividing cells (attached to centromere), dividing cells (at mitotic spindle) and ciliated cells (in cilia).
Describe the structure of microtubules.
Microtubule structure: composed of TUBULIN -alpha and Beta subunits Distinct ends: Plus end: adding alpha Minus end: removing Beta form Hollow tube (made of microtubule subunits) tubulin heterodimer- made of 1 alpha, 1 beta subunit.
Describe the structure of microtubules.
Microtubule structure: composed of TUBULIN -alpha and Beta subunits Distinct ends: Plus end: adding alpha Minus end: removing Beta form Hollow tube (made of microtubule subunits) HAS POLARITY. tubulin heterodimer- made of 1 alpha, 1 beta subunit.
Describe the structure of centrosome and how it relates to microtubules. Where do microtubules grow?
Centrosome:
contain a pair of centrioles
-only in animal cells.
-controls the length, number and orientation of microtubules.
has gamma tubulin rings.
The microtubules grow at their plus ends from gamma tubulin ring complexes of centrosome.
What kind of drugs affect microtubules and are used?
Drugs that prevent normal microtubule turnover inhibit mitosis
- anti-cancer drugs
1. Taxol- binds to microtubules, PREVENTS DIASSEMBLY
2. Colchicine- binds free tubulin, PREVENTS POLYMERIZATION.
What kind of drugs affect microtubules and are used?
Drugs that prevent normal microtubule turnover inhibit mitosis
- anti-cancer drugs- drugs inhibit rate of division in cancer cells.
1. Taxol- binds to microtubules, PREVENTS DIASSEMBLY
2. Colchicine- binds free tubulin, PREVENTS POLYMERIZATION.
Which cell would have longest microtubules?
one cell treated with taxol (prevents disassembly of microtubules)
Describe the role of microtubules in motor proteins. what are the two types of Motor proteins and how do they differ?
The motor proteins depend on ATP hydrolysis. 2 types of motor proteins: 1. Kinesin- move towards PLUS end -away from cell body. 2. Dyneins- moves towards MINUS end -TOWARDS cell body.
Describe what cilia and flagella is and how it relates to microtubules.
Cilia are shorter and more numerous than flagella.
flagella- long, structures.
“9+ 2” arrangement
- 2 microtubules in center of flagella, then 9 pairs (alpha, beta tubules) of microtubules are around center
CILIARY DYNEIN generates movement in cilia.
Describe what cilia and flagella is and how it relates to microtubules.
Cilia are shorter and more numerous than flagella.
flagella- long, structures.
“9+ 2” arrangement
- 2 microtubules in center of flagella, then 9 pairs (alpha, beta tubules) of microtubules are around center
CILIARY DYNEIN generates movement in cilia.
in normal flagellum, dynein causes microtubule bending.
What occurs when there is mutation in motor protein? mutation in ciliary dynein?
mutation in motor protein- microtubules slide against each other,
occur in male infertility: sperm has normal shape, but not able to penetrate or travel to egg due to mutation in motor protein.
mutation in ciliary dynein- inability to clear out mucus.
What are major functions of microtubules?
organize centrosomes, organize cell interior, motor proteins drive intracellular transport, allow cell to move (cilia and flagella).
Where are actin filaments seen in?
Actin filaments- thin and flexible
-seen in”
microvilli (no movement, increase SA, for absorption)
- seen in contractile bundles
-filopodia (cell movement)
-contractile ring- ( 2 PM pinch together to from new daughter cells after mitosis; formed by alpha and beta cells)
What is the structure of actin?
Actin filaments are thinner than microtubules
-occur in bundles
-Orientation:
plus end: growth
minus end: disassembly
the growth of actin or disassembly depends on ATP HYDROLYSIS.
When actin bound ATP, grow on plus end; while actin bound to ADP will dissociate on minus end.
