Membranes

Question 0

Red blood cell

Answer 0

Pure membrane fraction - ideal
> large numbers
> anucleate, no organelles
> easy to manipulate. Turn inside out, fluorescently tagged molecules to tell which membrane is outside

Question 1

nAChR specificity

Answer 1

Experimentally reversing the negative charge residues at the mouth of the nAChR channel with site-directed mutagenesis can turn it into an anion-selective channel

Question 2

Evidence for bilateral

Answer 2

EM. Black dense precipice with osmium tetroxide
–> measure distance between phospholipid bilayer
Calculation with RBC. Measure of SA and number of phospholipids –> bilayer

Question 3

Proteins are mobile

Answer 3

Fuse mouse and human cell
Add coloured antibodies
Incubate at 37
After 40 minutes will have visible jumbled

Question 4

Freeze-fracturing uses TEM

Answer 4

Living material in liquid nitrogen, frozen along lines of weaknesses, fractured surfaces ‘etched’ with heavy metal –> TEM –> tiny dots of protein, not uniform

Question 5

Lipid fluidity

Answer 5

Liposome - spherical vesicles or black membrane - formed across hole in partition between 2 aqueous compartments
Fluorescent dye/gold particle attached to play head. Rapid lateral diffusion

Question 6

FRAP

Answer 6

Fluorescence recovery after photobleaching
Lateral mobility - labelled with fluorophores/fluorescent anitbodies
Short pulse of laser light –> photobleaches
–> fluorophores gradually return to area

Question 7

Membrane skeleton fence

Answer 7

Kusumi et al
Partial destruction of cytoskeleton decreases fraction of confined molecules and truncation of the cytoplasmic domain leads to less confined diffusion. Supported by laser trap technique - drags labelled proteins using a laser light