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Cell Biology (grad) > CYTOSKELETON > Flashcards

CYTOSKELETON Flashcards

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1
Q

Describe the structure and function of intermediate filaments

A

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.

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2
Q

Explain the process of Dynamic instability in mircotubules

A

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.

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3
Q

Compare kinesin and Dynein activity

A

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.

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4
Q

Illustrate the activity of cilia and flagella

A

Cilia- movement, clearing mucus.
flagella- locomotion/movement of cell
ex: sperm cell

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5
Q

recognize actin filament structure and treadmilling

A

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.

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6
Q

Diagram the proteins and actions involved in muscle contraction

A

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.

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7
Q

Evaluate the action of various pharmacological agents on cytoskeletal activity.

A

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.
d

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8
Q

What is a common accessory protein for intermediate filaments?

A

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

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9
Q

Describe the kind of intermediate filaments in nuclear lamina and the activity that occurs.

A

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.

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10
Q

What kind of pathologies are associated with intermediate filaments.

A

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.

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11
Q

what kind of cells do you see microtubules in?

A

Microtubules seen in nondividing cells (attached to centromere), dividing cells (at mitotic spindle) and ciliated cells (in cilia).

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12
Q

Describe the structure of microtubules.

A 
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.
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13
Q

Describe the structure of microtubules.

A 
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.
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14
Q

Describe the structure of centrosome and how it relates to microtubules. Where do microtubules grow?

A

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.

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15
Q

What kind of drugs affect microtubules and are used?

A

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.
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16
Q

What kind of drugs affect microtubules and are used?

A

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.
17
Q

Which cell would have longest microtubules?

A

one cell treated with taxol (prevents disassembly of microtubules)

18
Q

Describe the role of microtubules in motor proteins. what are the two types of Motor proteins and how do they differ?

A 
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.
19
Q

Describe what cilia and flagella is and how it relates to microtubules.

A

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.

20
Q

Describe what cilia and flagella is and how it relates to microtubules.

A

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.

21
Q

What occurs when there is mutation in motor protein? mutation in ciliary dynein?

A

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.

22
Q

What are major functions of microtubules?

A

organize centrosomes, organize cell interior, motor proteins drive intracellular transport, allow cell to move (cilia and flagella).

23
Q

Where are actin filaments seen in?

A

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)

24
Q

What is the structure of actin?

A

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.

25
Q

What are the unique things about each element of cytoskeleton?

A
  1. Intermediate filament- has phosphorylation which determines assembly or disassembly of filaments.
  2. Microtubules- Dynamic instability- growth and disassembly from ONE end due to GTP hydrolysis
  3. Actin- TREADMILLING, movement of monomers through filament (ATP hydrolysis)
26
Q

What are the unique things about each element of cytoskeleton?

A
  1. Intermediate filament- has PHOSPHORYLATION which determines assembly or disassembly of filaments.
  2. Microtubules- DYNAMIC INSTABILITY- growth and disassembly from ONE end due to GTP hydrolysis
  3. Actin- TREADMILLING, movement of monomers through filament (ATP hydrolysis)
27
Q

Describe the drugs that affect actin

A
  1. Phalloidin- binds and stabilizes filaments (can elongate)
  2. Cytochalasin- caps filament plus ends, PREVENTING polymerization
  3. Latrunculin- binds actin monomers, PREVENTS their POLYMERIZATION.
28
Q

Describe the drugs that affect actin

A
  1. Phalloidin- binds and stabilizes filaments (can elongate)
  2. Cytochalasin- caps filament plus ends, PREVENTING polymerization
  3. Latrunculin- binds actin monomers, PREVENTS their POLYMERIZATION.
    These drugs can be used as anti-cancer drugs that help reduce malignancy in cells (leave normal cell, migrate to other cell.
29
Q

Describe the growth of actin in cells.

A

Actin grows through treadmilling- movement of monomers through filament, ATP hydrolysis.
one end of filament actin grows, other end, actin shrinks.

30
Q

Describe the process of cell crawling actin

A

a

31
Q

Which kind of motor proteins are in actin, what role does it play?

A

a

32
Q

Describe the process of cell crawling actin

A 
Cell crawling in actin: process of extending lamellipodia (thin layer of actin), creating actin nucleation and filipodia may also form. 
-Attachments are made 
-contraction of distal end. 
-Actin polymerization pushes leading edge forward
Actin-related proteins (ARPs)
-Formins
-for straight filaments
-filapodia 
-contractile ring.
33
Q

Which kind of motor proteins are in actin, what role does it play?

A 
Motor protein in actin: 
Myosin- Hydrolyze ATP and move towards plus (+) end of actin filament.
two types of myosin: 
-Type I- seen in all cells
-Type II- seen in muscle cells.
34
Q

Describe actin signaling and which proteins are involved.

A

Rho proteins involved in actin signaling.
Rho proteins: monomeric GTPases activated by extracellular signals.
They control various processes like cytoskeleton reorganization.
For cells to migrate in one direction, it must be activated by extracellular signal.

35
Q

What occurs during muscle contraction? Which proteins are included? what are the 3 major types of muscle cells?

A 
During muscle contraction: 
- Interactions between actin and myosin fibers 
-actin slides against myosin
-muscle contraction triggered by Cytosolic INCREASE in Ca^2+
3 types of major muscle cells: 
1. Skeletal (voluntary)
2. Cardiac (involuntary contraction)
3. Smooth (involuntary contraction)

Myosin II in muscle cells are dimers made of globular ATPase head with coiled tail.
Myosin movement depends on ATP hydrolysis.

36
Q

What is the function of sarcomere? distinguish between two types of filaments in sarcomeres.

A

sarcomere- contractile unit of muscle cells; that is also functional unit of skeletal muscle.
Two types of filaments in sarcomere:
1. Thick filaments- myosin
2. Thin filaments- actin

37
Q

Describe the process of muscle contraction

A

Muscle contraction is triggered by increase in Cytosolic Ca^2+.

  1. Calcium binds to troponin
  2. moves tropomyosin
  3. reveals myosin binding site.

Cell Biology (grad) (16 decks)

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