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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
What is cortical actin?
Envelope of actin around the cell which gives the cell its shape (crosslinks)
26
What are stress fibres?
Antiparallel contractile bundles of actin within cell
27
How much of our body is cells?
50%
28
What are the 3 types of extracellular matrix?
- Fibrous proteins - Adhesion proteins - Hydrated macromolecules
29
What are the 2 types of fibrous proteins?
- Collagens | - Elastin
30
What is the main component of the extracellular matrix?
Collagen
31
What is the structure of collagen?
- Glycine-proline-hydroxyproline triplet repeats - Triple helix - 3 alpha chains
32
Which cells produce collagen?
- Fibroblasts | - Epithelial cells
33
What syndrome arises from collagen defects?
Ehlers-Danlos syndrome | Vascular form causes arterial rupture
34
How is elastin formed?
Oxidation of tropoelastin into elastin with the enzyme lysyl oxidase
35
Which protein makes up 50% of the dry weight of the aorta?
Elastin
36
How does elastin stretch?
Single elastin molecules are connected by cross-links which allows elastin to gain structure as it stretches.
37
What protein forms the scaffold for elastin?
Fibrillin
38
What syndrome arises from defects in fibrillin?
Marfan syndrome
39
What are the 2 types of hydrated macromolecules in the extracellular matrix?
- Glycosaminoglycans (GAG) | - Proteoglycans (GAG + a protein)
40
What is a proteoglycan?
A core protein with one or more GAG chains covalently bonded.
41
What is a glycosaminoglycan?
A long linear polysaccharide consisting of repeating disaccharide units. Disaccharide is made of a uronic sugar and an amino sugar.
42
What are the properties of GAGs?
- Negatively charged | - Very hydrophilic
43
What is hyaluronan?
Also known as hyaluronic acid. | A type of GAG.
44
What is the structure of hyaluronan?
- 250 000 sugars long (big) - Not sulphated (only hydroxyl groups) - Holds hydrated spaces
45
What are the 2 types of adhesion glycoproteins?
- Laminin | - Fibronectin
46
What is the main feature of laminin and fibronectin?
Have integrin receptor binding sites for binding to cell membranes.
47
What does integrin do?
Transmembrane receptor proteins that connect the actin cytoskeleton to the extracellular matrix.
48
What is the structure of integrin?
- Cations for binding to -ve ECM | - Heterodimers (alpha and beta subunits)
49
What are focal adhesions?
Mechanical links between actin bundles and the extracellular matrix which contain integrin
50
What are the components of focal adhesions?
- Talin - Alpha actinin - Vinculin - Focal adhesion kinase (signalling)
51
What are the 3 types of cell junctions?
- Adherens junction - Tight junction - Gap junction
52
What is cadherin?
Transmembrane adhesion proteins that mediate cell-cell adhesion
53
What are the properties of cadherin?
- Calcium dependent - Homophilic interaction (cell sticking to cell) - Links to actin cytoskeleton
54
Which type of junction is cadherin involved in?
Adherens junction
55
What is catenin?
Cadherin binds to catenin which then binds to the actin cytoskeleton
56
What is a hemidesmosome?
Attaches epithelial cells to the basal lamina using integrins and intermediate filaments (cytoskeleton but not actin/microtubules)
57
What is a desmosome?
A cell-cell junction involving cadherins and intermediate filaments
58
What is cadherin?
Transmembrane adhesion protein that mediates cell-cell adhesion.
59
What is an example of an intermediate filament?
Keratin
60
What is an example of an autoimmune disease which targets the cadherin protein desmoglein? (in desmosomes)
Pemphigus- skin blistering
61
What is the purpose of tight junctions?
Forms barriers to stop things leaking through
62
Where in the body do you find desmosomes? (2)
Cardiac muscle and epidermis (undergo mechanical stress so need stronger cell-cell adhesions)
63
Where do you find tight junctions?
Epithelia e.g. gut
64
What is transcellular transport?
Transport across the epithelium by passing through the epithelial cell.
65
What is paracellular transport?
Transport across the epithelium by passing between the epithelial cells.
66
What are the 2 proteins involved in tight junctions?
Occludin and claudin
67
What part of the cytoskeleton is involved in tight junctions?
Actin
68
What are zonula occludens proteins?
Bind occludin/claudin to actin in tight junctions
69
What is the purpose of gap junctions?
Communication
70
Where in the body do you fine gap junctions?
Anywhere that does cell-cell communication
71
Which proteins make up gap junctions?
Connexins
72
How many connexins make one connexon?
6

Mol Cell Bio (7 decks)

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