Lecture 2.1 - Vesicles Flashcards
Curvature: what features of membranes affect it?
- Size - smaller membranes = greater degree of curvature
- Leaflet - inner leaflet = GDoC
- Lipid type - some lipids = GDoC
Vesicle budding: how big are the buds, what notable features are there, and why does this occur?
~60nm
1.5x more lipid than in outer leaflet - allows for greater curvature
Allows for a greater degree of positive curvature so the new vesicle can be formed
Vesicle budding: is positive curvature enough for vesicle formation?
No - negative curvature also needs to be generated
Lipids: are there typical lipids which are localised to certain leaflets?
Outer leaflet:
* Phosphatidylcholines (~60%)
* Sphingomyelins (~30%)
* Glycolipids (~10%)
Inner leaflet:
* Phosphatidylserines (~60%)
* Phosphatidylethanolamine (~40%)
* Phosphatidylinotisol
Generating positive curvature: how does it work?
Multiple ways to do so:
- Movement of inner leaflet lipids to the outer leaflet
- Using lipids to influence curvature
Flippase and floppase: what are they and what do they do?
Flippase (aminophospholipid translocators) - flip lipids from the outer leaflet to the inner leaflet using ATP - form of producing negative curvature
Floppase (ATP-binding casette (ABC) transproters) - move lipids from the inner leaflet to the outer leaflet using ATP - form of producing positive curvature
How do lipids cause curvature?
Each lipid has different shapes due to the relative size of their head/tail(s)
- Equal split between head and tails, no curvature - ie phosphatidylcholine
- Bigger head than tail, positive curvature - ie lysophosphatidylcholine and sphingomyelin
- Smaller head than tails, negative curvature - ie phosphatidylethanolamine
Cholesterol: how does it move between membrane leaflet layers?
It can spontaneously move between leaflets - can be useful for quick adjustments
Phospholipases: what types are there and what do they form?
Phospholipase A - lysophospholipds
Phospholipase C - diacylglycerol
Phospholipase D - phosphatidate
