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Biochemistry > Lecture 9 > Flashcards

Lecture 9 Flashcards

1
Q

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

A

Polar, treadmilling

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2
Q

The side that F-actin grows at is what end

A

Barbed or + end

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3
Q

The side that F-actin shortens at is what end

A

Pointed or - end

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4
Q

An unbound actin is called what

A

G-actin (globular)

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5
Q

Filamentous actin relies on what

A

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

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6
Q

A actin bundle is called what

A

Stress fiber

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7
Q

What is a focal adhesion

A

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

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8
Q

Myosin/ F-actin binding facilitates what

A

Intracellular movements

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9
Q

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

A

Class 2

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10
Q

What is dystrophin

A

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.

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11
Q

Microtubules are composed of what

A

Tubulin dimers

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12
Q

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

A

Microtubules

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13
Q

Microtubules are composed of what

A

alpha/ beta dimers paired into13 linear protofilaments arranged in parallel

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14
Q

What controls microtubule polymerization

A

GTP hydrolysis

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15
Q

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

A

Positive end

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16
Q

Centrosome or ________ anchors
microtubules

A

Microtubule organizing center (MTOC)

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17
Q

MTOC positive and negative ends are where

A

Positive to periphery and negative near nucleus

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18
Q

What stabilizes the negative ends near the nucleus of the microtubules

A

2 centrioles arranged orthogonally

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19
Q

Anti-tubulin therapeutics disrupt _______ formation

A

Mitotic spindle

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20
Q

Colchicine:

A

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

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21
Q

Vincristine

A

Causes nonspecific tubulin aggregation (tumors)

22
Q

Taxol

A

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

23
Q

Mebendazole:

A

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

24
Q

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

A

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

25
Q

Axonemal microtubules: central shaft (or axoneme) of ______

A

Cilia and flagella

26
Q

An axoneme has what pattern

A

9+2

27
Q

Axonemal movement powered by ______

A

Dynein

28
Q

Kartagener syndrome:

A

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

29
Q

What are intermediate filaments for & what are 3 examples

A

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

30
Q

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

A

Microtubules> intermediate filaments> F-actin

31
Q

Desmosomes and hemidesmosomes anchor _______

A

Intermediate filaments

32
Q

Desmosomes provide cell-to-cell
contacts by linking _______

A

Intermediate filaments and transmembrane proteins

33
Q

Hemidesmosomes:

A

Provide cell-to extracellular matrix anchoring

34
Q

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

A

Epidermolysis bullosa simplex (EBS)

35
Q

What are the 2 roles of the Golgi

A

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

36
Q

What is the mechanism that proteins get localized to the ER

A

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

37
Q

The secretory pathway is the ________________ and used when

A

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

38
Q

Regulated exocytosis is always mediated through what & stored until when

A

Calcium signalling, stored until they get an extracellular signal

39
Q

For regulated exocytosis what open the calcium channels

A

Depolarization

40
Q

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

A

Cis-golgi network

41
Q

Where does protein come out in linear fashion

A

ER

42
Q

What is the site of macromolecule degradation

A

Lysosome

43
Q

What maintains the pH of a lysosome

A

H+ATPase (H pump)

44
Q

What is the tag that targets proteins for lysosome

A

Mannose 6 phosphate

45
Q

What is the process for a M6P tag being put on

A

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

46
Q

What is the underlying mechanism of I-cell disease

A
  • Mannose 6-PO4 tag failure in Golgi
  • Acid hydrolases are not incorporated into lysosome
  • Undegraded macromolecules accumulate
47
Q

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

A

Deficiency: Glucocerebrosidase
Accumulating sphingolipid: Glucosylceramide

48
Q

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

A

Deficiency: Sphingomyelinase
Accumulating sphingolipid: Sphingomyelin

49
Q

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

A

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

50
Q

Gaucher disease facts

A

-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

51
Q

Acid hydrolases in a lysosome are around what pH

A

5

Biochemistry (21 decks)

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