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Mol Cell Bio > Dr Bass > Flashcards

Dr Bass Flashcards

1
Q

What are the 2 methods of cell motility?

A
  • Swimming

- Crawling

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2
Q

Which protein filaments are used for swimming?

A

Microtubules

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3
Q

Which protein filaments are used for crawling?

A

Actin

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4
Q

What proteins are microtubules made from?

A

Hollow tubes of α and β tubulin dimers (heterodimeric)

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5
Q

Which structures do microtubules form?

A

Cilia and flagella (same structure but cilia are shorter)

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6
Q

What energy source molecule does tubulin contain?

A

GTP (hydrolysed to GDP during polymerisation of microtubule)

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7
Q

How many protofilaments makes up a microtubule in a cell?

A

13

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8
Q

What is the axoneme?

A

Core microtubule structure of the flagella/cilia

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9
Q

What is the arrangement of microtubules in the axoneme called?

A

9+2 (9 outer doublets + inner pair)

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10
Q

What are the 9 outer doublets of the axoneme made from?

A

A fibre (13 protofilaments) and B fibre (10 protofilaments)

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11
Q

What is the motor protein associated with microtubules?

A

Dynein

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12
Q

How does dynein cause movement in cilia/flagella?

A
  • Dynein arms connect adjacent doublets
  • Hydrolyse ATP to release energy
  • Doublets slide past each other
  • Linking proteins cause microtubules to bend
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13
Q

What is the basal body?

A
  • Connects the flagellum to the inner cytoskeleton of the cell (avoids tearing the plasma membrane)
  • Modified centriole
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14
Q

What is the microtubule arrangement of the basal body?

A

9x3 (no central pair, 9 outer triplets)

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15
Q

What is a centrosome?

A
  • Contains 2 centrioles

- Organises microtubules

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16
Q

What is the structure of actin filaments?

A
  • Not hollow
  • Polar (+ve/-ve ends)
  • ATP present in subunit (hydrolysed to ADP when polymerised to form a filament)
  • Actin monomers (homomeric)
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17
Q

What is the function of profilin?

A

Binds to ATP form of actin subunit to inhibit polymerisation

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18
Q

What is the function of cofilin?

A

Binds to actin filament and causes severing

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19
Q

What is the motor protein associated with actin?

A

Myosin

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20
Q

What are the ways that actin can cause movement?

A
  • Treadmilling

- Dragging with mysosin

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21
Q

Describe the interaction of actin and myosin to cause movement.

A
  • Troponin/tropomyosin complex blocks myosin binding site
  • Calcium binds to t/t complex to= exposes binding site
  • Myosin head binds (cross-bridge) and hydrolyses ATP to ADP which causes the power stroke
  • ATP binds to myosin to break cross-bridge
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22
Q

What are the 4 actin structures?

A
  • Filopodium
  • Lamellipodium
  • Stress fibres
  • Cortical actin
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23
Q

What are filopodia?

A

Membrane protrusions for exploration which extend beyond the lamellipodia (parallel bundles of actin) e.g. extending towards a growth factor stimulus

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24
Q

What are lamellipodia?

A

Wave-like actin cytoskeletal projections in a migrating cell (crosslinks of actin)

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25
Q

What is cortical actin?

A

Envelope of actin around the cell which gives the cell its shape (crosslinks)

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26
Q

What are stress fibres?

A

Antiparallel contractile bundles of actin within cell

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27
Q

How much of our body is cells?

A

50%

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28
Q

What are the 3 types of extracellular matrix?

A
  • Fibrous proteins
  • Adhesion proteins
  • Hydrated macromolecules
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29
Q

What are the 2 types of fibrous proteins?

A
  • Collagens

- Elastin

30
Q

What is the main component of the extracellular matrix?

31
Q

What is the structure of collagen?

A
  • Glycine-proline-hydroxyproline triplet repeats
  • Triple helix
  • 3 alpha chains
32
Q

Which cells produce collagen?

A
  • Fibroblasts

- Epithelial cells

33
Q

What syndrome arises from collagen defects?

A

Ehlers-Danlos syndrome

Vascular form causes arterial rupture

34
Q

How is elastin formed?

A

Oxidation of tropoelastin into elastin with the enzyme lysyl oxidase

35
Q

Which protein makes up 50% of the dry weight of the aorta?

36
Q

How does elastin stretch?

A

Single elastin molecules are connected by cross-links which allows elastin to gain structure as it stretches.

37
Q

What protein forms the scaffold for elastin?

38
Q

What syndrome arises from defects in fibrillin?

A

Marfan syndrome

39
Q

What are the 2 types of hydrated macromolecules in the extracellular matrix?

A
  • Glycosaminoglycans (GAG)

- Proteoglycans (GAG + a protein)

40
Q

What is a proteoglycan?

A

A core protein with one or more GAG chains covalently bonded.

41
Q

What is a glycosaminoglycan?

A

A long linear polysaccharide consisting of repeating disaccharide units.
Disaccharide is made of a uronic sugar and an amino sugar.

42
Q

What are the properties of GAGs?

A
  • Negatively charged

- Very hydrophilic

43
Q

What is hyaluronan?

A

Also known as hyaluronic acid.

A type of GAG.

44
Q

What is the structure of hyaluronan?

A
  • 250 000 sugars long (big)
  • Not sulphated (only hydroxyl groups)
  • Holds hydrated spaces
45
Q

What are the 2 types of adhesion glycoproteins?

A
  • Laminin

- Fibronectin

46
Q

What is the main feature of laminin and fibronectin?

A

Have integrin receptor binding sites for binding to cell membranes.

47
Q

What does integrin do?

A

Transmembrane receptor proteins that connect the actin cytoskeleton to the extracellular matrix.

48
Q

What is the structure of integrin?

A
  • Cations for binding to -ve ECM

- Heterodimers (alpha and beta subunits)

49
Q

What are focal adhesions?

A

Mechanical links between actin bundles and the extracellular matrix which contain integrin

50
Q

What are the components of focal adhesions?

A
  • Talin
  • Alpha actinin
  • Vinculin
  • Focal adhesion kinase (signalling)
51
Q

What are the 3 types of cell junctions?

A
  • Adherens junction
  • Tight junction
  • Gap junction
52
Q

What is cadherin?

A

Transmembrane adhesion proteins that mediate cell-cell adhesion

53
Q

What are the properties of cadherin?

A
  • Calcium dependent
  • Homophilic interaction (cell sticking to cell)
  • Links to actin cytoskeleton
54
Q

Which type of junction is cadherin involved in?

A

Adherens junction

55
Q

What is catenin?

A

Cadherin binds to catenin which then binds to the actin cytoskeleton

56
Q

What is a hemidesmosome?

A

Attaches epithelial cells to the basal lamina using integrins and intermediate filaments (cytoskeleton but not actin/microtubules)

57
Q

What is a desmosome?

A

A cell-cell junction involving cadherins and intermediate filaments

58
Q

What is cadherin?

A

Transmembrane adhesion protein that mediates cell-cell adhesion.

59
Q

What is an example of an intermediate filament?

60
Q

What is an example of an autoimmune disease which targets the cadherin protein desmoglein? (in desmosomes)

A

Pemphigus- skin blistering

61
Q

What is the purpose of tight junctions?

A

Forms barriers to stop things leaking through

62
Q

Where in the body do you find desmosomes? (2)

A

Cardiac muscle and epidermis (undergo mechanical stress so need stronger cell-cell adhesions)

63
Q

Where do you find tight junctions?

A

Epithelia e.g. gut

64
Q

What is transcellular transport?

A

Transport across the epithelium by passing through the epithelial cell.

65
Q

What is paracellular transport?

A

Transport across the epithelium by passing between the epithelial cells.

66
Q

What are the 2 proteins involved in tight junctions?

A

Occludin and claudin

67
Q

What part of the cytoskeleton is involved in tight junctions?

68
Q

What are zonula occludens proteins?

A

Bind occludin/claudin to actin in tight junctions

69
Q

What is the purpose of gap junctions?

A

Communication

70
Q

Where in the body do you fine gap junctions?

A

Anywhere that does cell-cell communication

71
Q

Which proteins make up gap junctions?

72
Q

How many connexins make one connexon?

Mol Cell Bio (7 decks)

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