1. Disc-shaped phospholipid particles, called bicelles, can be used to mimic mem

Question

1. Disc-shaped phospholipid particles, called bicelles, can be used to mimic membrane bilayers in order to study protein-membrane interactions in vitro. Bicelles are flattened micelles that look like a pancake (~40 A thick; lipid bilayer is 36 A thick). bicelle 40A a) If each methylene (-CH) group in a straight-chain hydrocarbon advances the chain length by about is this? (Note, you should consider the terminal carboxylic acid C as a methylene group.) (5 pts) 0.13 nm, what length fatty acid would most likely be found in each half of the bicelle? What fatty acid b) Would you come to the same conclusion for a typical plasma membrane? If not, which length fatty acid(s) would you likely find in a typical cellular membrane? Show calculations and explain. (3 pts)

Explanation / Answer

Answer:

1. a. The length of the bicelle is 40 angstroms. So, the length of the fatty acid that can be found cannot be more than 20 angstroms, considering the overlap.

C15 fatty acid gives a length of = 0.13 nm x 15 = 1.95 nm = 19.5 angstroms

So, a maximum of C15 fatty acid can be accomodated in the bicelle in each layer.

Thus, the fatty acid appears to be Pentadecanoic acid (Pentadecylic acid).

b. Considering the width of a cell membrane (lipid bilayer) to be 36 angstroms (given in the question), a fatty acid not more than 18 angstroms can be accommodated in each layer of the cell membrane.

Length of the fatty acid that can be accommodated = 13 x 0.13 nm = 1.69 nm = 16.9 angstroms

So, the length of the fatty acid expected to be found in a typical cell membrane is 13 C.

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