Lecture 9

Question 1

F-actin is a _______ filament, able to grow and shorten (________)

Answer 1

Polar, treadmilling

Question 2

The side that F-actin grows at is what end

Answer 2

Barbed or + end

Question 3

The side that F-actin shortens at is what end

Answer 3

Pointed or - end

Question 4

An unbound actin is called what

Answer 4

G-actin (globular)

Question 5

Filamentous actin relies on what

Answer 5

ATP to bind to a G-actin and exchange it for ADP

Question 6

A actin bundle is called what

Answer 6

Stress fiber

Question 7

What is a focal adhesion

Answer 7

Sites of attachment linking actin,
transmembrane proteins and the
extracellular matrix

Question 8

Myosin/ F-actin binding facilitates what

Answer 8

Intracellular movements

Question 9

What class of myosin/ F-actin is involved in muscle contraction

Answer 9

Class 2

Question 10

What is dystrophin

Answer 10

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.

Question 11

Microtubules are composed of what

Answer 11

Tubulin dimers

Question 12

alpha/beta-tubulin heterodimer form head-to-tail polymers to form ______

Answer 12

Microtubules

Question 13

Microtubules are composed of what

Answer 13

alpha/ beta dimers paired into13 linear protofilaments arranged in parallel

Question 14

What controls microtubule polymerization

Answer 14

GTP hydrolysis

Question 15

alpha/beta-tubulin dimer with GTP bound to
beta-tubulin binds on what end of the microtubule

Answer 15

Positive end

Question 16

Centrosome or ________ anchors
microtubules

Answer 16

Microtubule organizing center (MTOC)

Question 17

MTOC positive and negative ends are where

Answer 17

Positive to periphery and negative near nucleus

Question 18

What stabilizes the negative ends near the nucleus of the microtubules

Answer 18

2 centrioles arranged orthogonally

Question 19

Anti-tubulin therapeutics disrupt _______ formation

Answer 19

Mitotic spindle

Question 20

Colchicine:

Answer 20

Binds a- and b-tubulin, inhibits polymerization (gout)

Question 21

Vincristine

Answer 21

Causes nonspecific tubulin aggregation (tumors)

Question 22

Taxol

Answer 22

Promotes microtubule stabilization; cells “stuck” in mitosis (tumors)

Question 23

Mebendazole:

Answer 23

Binds b-tubulin of parasitic worms and less so to mammalian microtubules, disrupts microtubule function (Antihelminthic therapy)

Question 24

_______ and _______ move
along microtubule tracks
in opposing directions, what direction do they move in

Answer 24

Dynein (towards negative end) and Kinesin (towards positive end)

Question 25

Axonemal microtubules: central shaft (or axoneme) of ______

Answer 25

Cilia and flagella

Question 26

An axoneme has what pattern

Answer 26

9+2

Question 27

Axonemal movement powered by ______

Answer 27

Dynein

Question 28

Kartagener syndrome:

Answer 28

Dynein defect in flagella (sperm) and cilia (respiratory tract), decrease in fertility in males (immotile sperm) and females (dysfunctional fallopian tube cilia)

Question 29

What are intermediate filaments for & what are 3 examples

Answer 29

Structural support & mechanical strength Keratin (epithelial cells) Vimentin (fibroblasts) Neurofilaments (neurons)

Question 30

What is the order of size of intermediate filaments, F-actin, and microtubules

Answer 30

Microtubules> intermediate filaments> F-actin

Question 31

Desmosomes and hemidesmosomes anchor _______

Answer 31

Intermediate filaments

Question 32

Desmosomes provide cell-to-cell contacts by linking _______

Answer 32

Intermediate filaments and transmembrane proteins

Question 33

Hemidesmosomes:

Answer 33

Provide cell-to extracellular matrix anchoring

Question 34

Mutations to keratin intermediate filaments prevent assembly of strong IF networks in epithelial cells and can cause what

Answer 34

Epidermolysis bullosa simplex (EBS)

Question 35

What are the 2 roles of the Golgi

Answer 35

Post-translational modifications, protein sorting to final intracellular or extracellular destinations

Question 36

What is the mechanism that proteins get localized to the ER

Answer 36

1- KDEL sequence signals return to ER 2- KDEL receptors recognize sequence 3- Resident ER proteins return to ER

Question 37

The secretory pathway is the ________________ and used when

Answer 37

Default pathway, when localization signal is absent (this pathway is constitutively active [always on])

Question 38

Regulated exocytosis is always mediated through what & stored until when

Answer 38

Calcium signalling, stored until they get an extracellular signal

Question 39

For regulated exocytosis what open the calcium channels

Answer 39

Depolarization

Question 40

Newly synthesized lipids/ proteins from ER continuously arrive and fuse at the ____

Answer 40

Cis-golgi network

Question 41

Where does protein come out in linear fashion

Answer 41

ER

Question 42

What is the site of macromolecule degradation

Answer 42

Lysosome

Question 43

What maintains the pH of a lysosome

Answer 43

H+ATPase (H pump)

Question 44

What is the tag that targets proteins for lysosome

Answer 44

Mannose 6 phosphate

Question 45

What is the process for a M6P tag being put on

Answer 45

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

Question 46

What is the underlying mechanism of I-cell disease

Answer 46

* Mannose 6-PO4 tag failure in Golgi * Acid hydrolases are not incorporated into lysosome * Undegraded macromolecules accumulate

Question 47

What is the lysosomal enzyme deficiency and the accumulating sphingolipid involved with Gaucher disease

Answer 47

Deficiency: Glucocerebrosidase Accumulating sphingolipid: Glucosylceramide

Question 48

What is the lysosomal enzyme deficiency and the accumulating sphingolipid involved with Niemann- Pick disease (childhood alzheimer's)

Answer 48

Deficiency: Sphingomyelinase Accumulating sphingolipid: Sphingomyelin

Question 49

What is the lysosomal enzyme deficiency and the accumulating GAG involved with Hurler syndrome

Answer 49

Deficiency: alpha-Iduronidase Accumulating GAG: Heparan sulfate and dermatan sulfate

Question 50

Gaucher disease facts

Answer 50

-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

Question 51

Acid hydrolases in a lysosome are around what pH

Answer 51

5