The membrane
1.[2p] What actually drives phospholipids to assemble into a bilayer in water?
What actually drives phospholipids to assemble into a bilayer in water?
The answer is: The entropy gained when water ordered around the hydrocarbon chains is released
The answer is: The entropy gained when water ordered around the hydrocarbon chains is released
The answer is: The entropy gained when water ordered around the hydrocarbon chains is released
2.[1p] Gorter and Grendel's 1925 experiment contained two errors whose effects largely cancelled.
Gorter and Grendel's 1925 experiment contained two errors whose effects largely cancelled.
The answer is: True
3.[2p] Why does a two-tailed phospholipid form sheets while a single-tailed detergent forms small micelles?
Why does a two-tailed phospholipid form sheets while a single-tailed detergent forms small micelles?
The answer is: A two-tailed lipid is roughly cylindrical and packs flat, while a wedge-shaped detergent packs into a sphere
The answer is: A two-tailed lipid is roughly cylindrical and packs flat, while a wedge-shaped detergent packs into a sphere
The answer is: A two-tailed lipid is roughly cylindrical and packs flat, while a wedge-shaped detergent packs into a sphere
4.[3p] A red blood cell has about 140 µm² of membrane, and each lipid occupies 0.65 nm² of one leaflet. How many lipid molecules does the bilayer contain, in units of ?
A red blood cell has about 140 µm² of membrane, and each lipid occupies 0.65 nm² of one leaflet. How many lipid molecules does the bilayer contain, in units of ?
5.[2p] Which observations argued against the Danielli and Davson sandwich model of the membrane?
Which observations argued against the Danielli and Davson sandwich model of the membrane?
Select all that apply
The answer is: Purified membrane proteins turned out to be largely hydrophobic on their outer surfaces, Freeze-fracture microscopy showed particles inside the membrane interior
The answer is: Purified membrane proteins turned out to be largely hydrophobic on their outer surfaces, Freeze-fracture microscopy showed particles inside the membrane interior
6.[2p] Frye and Edidin fused a mouse cell to a human cell and labelled the surface proteins of each with a different dye. What happened within forty minutes at 37 degrees Celsius?
Frye and Edidin fused a mouse cell to a human cell and labelled the surface proteins of each with a different dye. What happened within forty minutes at 37 degrees Celsius?
The answer is: The two labels intermixed completely over the whole hybrid surface
The answer is: The two labels intermixed completely over the whole hybrid surface
The answer is: The two labels intermixed completely over the whole hybrid surface
7.[2p] Match each membrane to its approximate protein content by mass.
Match each membrane to its approximate protein content by mass.
Myelin
A typical plasma membrane
The inner mitochondrial membrane
18 per cent
76 per cent
50 per cent
Show the answer
Myelin: 18 per cent A typical plasma membrane: 50 per cent The inner mitochondrial membrane: 76 per cent
8.[3p] Why does a lipid bilayer exclude sodium so much more effectively than water?
Why does a lipid bilayer exclude sodium so much more effectively than water?
The answer is: A sodium ion must shed its hydration shell to enter a low-permittivity medium, which costs a very large energy
The answer is: A sodium ion must shed its hydration shell to enter a low-permittivity medium, which costs a very large energy
The answer is: A sodium ion must shed its hydration shell to enter a low-permittivity medium, which costs a very large energy
9.[1p] A phospholipid flips from one leaflet of a bilayer to the other about as easily as it diffuses sideways within a leaflet.
A phospholipid flips from one leaflet of a bilayer to the other about as easily as it diffuses sideways within a leaflet.
The answer is: False