Membrane lipids

Question 1

What controls membrane curvature?

Answer 1

Lipid composition
-lipids with heads smaller than tail make membrane curve outwards
-lipids with heads bigger than tail make membrane curve inwards
-lipids with heads similar size to tail don’t curve membrane

Membrane proteins
-if bigger at one side, curve membrane
(N/B: proteins can only be inserted into membrane in one direction)
-scaffolding (directed by peripheral proteins)
-helix insertion (inserting proteins which only go half way through membrane curves the membrane)

Cytoskeleton
-proteins in cytoskeleton push/pull membrane

Question 2

What does flippase do?

Answer 2

Flip lipids between bilayer leaflets
-not spontaneous (controlled by cell)
-dependent on ATP (requires energy to move hydrophilic head through hydrophobic inside of membrane)

Question 3

What does atomic force microscopy do?

Answer 3

Creates an image showing the different heights of components within a membrane
-shows types of lipids, where proteins are embedded, where membrane rafts are

Question 4

How does atomic force microscopy work?

Answer 4

-cantilever arm makes contact with surface of membrane
-piezoelectric scanner moves membrane surface backwards and forwards
-cantilever arm moves up and down as membrane is moved (as membrane surface isn’t flat)
-laser detects height of cantilever arm by laser being reflected off cantilever arm and detected