BC 9 Cytoskeleton

Question 1

Intermediate Filaments

Answer 1

Size: 8-10nm

Shape: Rope like

Compositions: Various protien filaments

Function: structure

anchors: desmosomes/hemidesmosomes (sites of stress)

NO polarity

Keratin (epithelium), Vimentin (non epithelial), neurofilament (neurons)

no cell movement

Question 2

Microtubules

Answer 2

Size: 20-25nm
Hollow Cylinders
Polymer of tubulin dimers (alpha and beta)
Function:
-intracellular transport via motor proteins
-chromosome segregation
-cilia and flagella

Anchors: Centrosome (minus end) (MTOC)
Bound via GTP and GTP hydrolic activity
alpga and beta

POLAR
Dynamic instability
kinesin -> +
dynein -> -

growth will continue with high amounts of GTP bound tubulin (GTP cap retained while adding)

Question 3

Actin Filaments

Answer 3

6-8nm
Double stranded, helical shape
polymer of Gactin
Function: structural, muscle contraction

Microvillus, lamellipodia, filapodia, muscle contraction
Anchored to adherens junction (?) & focal adhesions

bound by atp and atp hydrolytic activity (ATP favors polymerization

monomer- g actin
POLAR, dynamic instability
associated with MyoI and Myo II

Question 4

Epidermis Bullosa Simplex (HBS)

Answer 4

Keratins (IF)
mutations in keratin gene: abnormal assembly of keratin filaments in epidermis. (Cannot handle friction) Sheet of cells becomes damages, allowing fluid to escape and cause blisters

Keratin is an IF?

Question 5

Amyotrophic lateral Sclerosis (ALS) Leu G

Answer 5

mutations in neurofilamets (IF)

abnormal accumulation and assembly, progressive loss of motor neurons leading to muscle atrophy paralysis and death.

Question 6

MTOC

Answer 6

Microtubule organizing center
within centrosome
reach out frm centrosomes at various lengths
minus end higly unstable but anchored

Kinesin, moves items towards plus end
dynein, towards minus end

can have polarized form stabilized with capping proteins at plasma membrane

governs the location of organelles, provides framwork guiding cellular components

Question 7

Cilia and Flagella

Answer 7

Microtubules
Dynein: axenomal type, causes sliding of MT in axonemes of cilia and flagella

Cilia: 9+2 structure of tubes

dynein atpase?

Question 8

Kartagener Syndrome

Answer 8

absense of dynein in flagella dn cilia results in immotility and leads to sterility and chronic respitory infections

Question 9

Actin Assembly

Answer 9

Parallel Bundles: sheets of monomer held together by associated proteins (fimbrin) (microvilli/filapodia)

Contractile Bundles:Held together by aclpa actinin (stress fibers at focal adhesions)

Networks:Cell cortex, actin filament networks (?)

Question 10

muscle contraction

Answer 10

myofibrils contain actin bundles, myosin II displays atpase activity and moves along actin filament. Myosin II converts ATP to energy, generates force and movement. (many roles)

Question 11

Intracellular Transport

Answer 11

Myosin I moves along the actin filament with cargo (membrane vesicles). MyoI also requires ATP, not involved in muscle contraction

Question 12

GAG’s Glycosaminoglycans

Answer 12

Aka mucopolysaccharides

can have problems resulting in Hurlers syndrome or hunters syndrome,

buildup up heparin sulfate or dermatan sulfate in teh body, becuase of no breakdown of GAGs in the lysosome.

sugar chains (tons or rings) with N-glycosidic bonds

Question 13

Lipid Anchor

Answer 13

Myristic acid: n term
palmatic acid: internal
prenyl acid: c-term

Question 14

sphingolipidosis

Answer 14

Niemann-Pick disease Sphingomyelinase Sphingomyelin
Tay-Sachs disease Hexosaminidase A GM2-ganglioside
Gaucher disease -Glucosidase Glucosylceramide

Question 15

mucopolysaccharidosis

Answer 15

accumulating glycosaminoglycans (GAGs)

Hurler syndrome Iduronidase Heparan sulfate and dermatan sulfate (<50%)

Question 16

neurofiliment disorders

Answer 16

Amyotrophic lateral sclerosis (ALS, known as Lou Gehrig’s disease)
has been suggested to be a result of mutations in neurofilaments.
 Abnormal accumulation and assembly of neurofilaments cause
progressive loss of motor neurons, which in turn leads to muscle
atrophy, paralysis, and eventual death.

Question 17

Keratin disorder

Answer 17

Epidermolysis bullosa simplex (EBS) is caused by mutations in keratin
genes resulting in abnormal assembly of keratin filaments in the epidermis.
As a result, the skin is highly vulnerable to mechanical injury and even a
gentle pressure can rupture its cells, causing the skin to blister.

Question 18

KDEL

Answer 18

sends back along the dyein path, specific marker

Question 19

I cell disease

Answer 19

inclusion bodies from endocytosis and hydrolases go into blood stream