Lecture 9 Flashcards
F-actin is a _______ filament, able to grow and shorten (________)
Polar, treadmilling
The side that F-actin grows at is what end
Barbed or + end
The side that F-actin shortens at is what end
Pointed or - end
An unbound actin is called what
G-actin (globular)
Filamentous actin relies on what
ATP to bind to a G-actin and exchange it for ADP
A actin bundle is called what
Stress fiber
What is a focal adhesion
Sites of attachment linking actin,
transmembrane proteins and the
extracellular matrix
Myosin/ F-actin binding facilitates what
Intracellular movements
What class of myosin/ F-actin is involved in muscle contraction
Class 2
What is dystrophin
Actin-binding protein that links actin filaments
to transmembrane proteins of the muscle cell plasma membrane providing a link to the
extracellular matrix and stability during muscle contractions.
Microtubules are composed of what
Tubulin dimers
alpha/beta-tubulin heterodimer form head-to-tail polymers to form ______
Microtubules
Microtubules are composed of what
alpha/ beta dimers paired into13 linear protofilaments arranged in parallel
What controls microtubule polymerization
GTP hydrolysis
alpha/beta-tubulin dimer with GTP bound to
beta-tubulin binds on what end of the microtubule
Positive end
Centrosome or ________ anchors
microtubules
Microtubule organizing center (MTOC)
MTOC positive and negative ends are where
Positive to periphery and negative near nucleus
What stabilizes the negative ends near the nucleus of the microtubules
2 centrioles arranged orthogonally
Anti-tubulin therapeutics disrupt _______ formation
Mitotic spindle
Colchicine:
Binds a- and b-tubulin, inhibits polymerization (gout)
Vincristine
Causes nonspecific tubulin aggregation (tumors)
Taxol
Promotes microtubule stabilization; cells “stuck” in mitosis (tumors)
Mebendazole:
Binds b-tubulin of parasitic worms and less so to mammalian microtubules, disrupts microtubule function (Antihelminthic therapy)
_______ and _______ move
along microtubule tracks
in opposing directions, what direction do they move in
Dynein (towards negative end) and Kinesin (towards positive end)
Axonemal microtubules: central shaft (or axoneme) of ______
Cilia and flagella
An axoneme has what pattern
9+2
Axonemal movement powered by ______
Dynein
Kartagener syndrome:
Dynein defect in flagella (sperm) and cilia (respiratory tract), decrease in fertility in
males (immotile sperm) and
females (dysfunctional fallopian tube cilia)
What are intermediate filaments for & what are 3 examples
Structural support & mechanical strength
Keratin (epithelial cells)
Vimentin (fibroblasts)
Neurofilaments (neurons)
What is the order of size of intermediate filaments, F-actin, and microtubules
Microtubules> intermediate filaments> F-actin
Desmosomes and hemidesmosomes anchor _______
Intermediate filaments
Desmosomes provide cell-to-cell
contacts by linking _______
Intermediate filaments and transmembrane proteins
Hemidesmosomes:
Provide cell-to extracellular matrix anchoring
Mutations to keratin intermediate
filaments prevent assembly of strong IF
networks in epithelial cells and can cause what
Epidermolysis bullosa simplex (EBS)
What are the 2 roles of the Golgi
Post-translational modifications, protein sorting to final intracellular or extracellular destinations
What is the mechanism that proteins get localized to the ER
1- KDEL sequence signals return to ER
2- KDEL receptors recognize sequence
3- Resident ER proteins return to ER
The secretory pathway is the ________________ and used when
Default pathway, when localization signal is absent (this pathway is constitutively active [always on])
Regulated exocytosis is always mediated through what & stored until when
Calcium signalling, stored until they get an extracellular signal
For regulated exocytosis what open the calcium channels
Depolarization
Newly synthesized lipids/ proteins from ER continuously arrive and fuse at the ____
Cis-golgi network
Where does protein come out in linear fashion
ER
What is the site of macromolecule degradation
Lysosome
What maintains the pH of a lysosome
H+ATPase (H pump)
What is the tag that targets proteins for lysosome
Mannose 6 phosphate
What is the process for a M6P tag being put on
1-ER adds N-linked glycosylation
2- N-acetylglucosamine phosphates are added to mannose residues in cis-golgi
3- N-acetylglucosamine is removed leaving M6P
4-M6P is recognized by receptors in trans golgi
5- Receptor mediated transport to late endosome
6- Dissociation at acidic pH
7- Removal of phosphate
8- pH becomes more acidic through ATP dependent proton pump, activating hydrolases, converting endosome to lysosome
What is the underlying mechanism of I-cell disease
- Mannose 6-PO4 tag failure in Golgi
- Acid hydrolases are not incorporated into lysosome
- Undegraded macromolecules accumulate
What is the lysosomal enzyme deficiency and the accumulating sphingolipid involved with Gaucher disease
Deficiency: Glucocerebrosidase
Accumulating sphingolipid: Glucosylceramide
What is the lysosomal enzyme deficiency and the accumulating sphingolipid involved with Niemann- Pick disease (childhood alzheimer’s)
Deficiency: Sphingomyelinase
Accumulating sphingolipid: Sphingomyelin
What is the lysosomal enzyme deficiency and the accumulating GAG involved with Hurler syndrome
Deficiency: alpha-Iduronidase
Accumulating GAG: Heparan sulfate and dermatan sulfate
Gaucher disease facts
-Most common lysosomal storage disease
-Carriers of this disease are common among individuals with Ashkenazi Jewish ancestry (1 in 10)
-Affects spleen and liver macrophages due to their ingestion of large amounts of lipids
-Type 1: Liver and spleen enlargement
-Therapy: enzyme replacement therapy
Acid hydrolases in a lysosome are around what pH
5
