Becker's World of the Cell 9th Edition by Lewis Kleinsmith, Jeff Hardin, Gregory Paul Bertoni

Exercise 6

That's About the Size of It. From chemistry, we know that each methylene (-CH 2 -)group in a straight-chain hydrocarbon advances the chain length by about 0.13 nm. And from studies of protein structure, we know that one turn of an a helix includes 3.6 amino acid residues and extends the long axis of the helix by about 0.56 nm. Use this information to answer the following:
(a)How long is a single molecule of palmitate (16 carbon atoms)in its fully extended form What about molecules of laurate (12C)and arachidate (20C)
(b)How does the thickness of the hydrophobic interior of a typical membrane compare with the length of two palmitate molecules laid end to end What about two molecules of laurate or arachidate
(c)Approximately how many amino acids must a helical transmembrane segment of an integral membrane protein have if the segment is to span the lipid bilayer defined by two palmitate molecules laid end to end
(d)The protein bacteriorhodopsin has 248 amino acids and seven transmembrane segments. Approximately what portion of the amino acids are part of the transmembrane segments Assuming that most of the remaining amino acids are present in the hydrophilic loops linking the transmembrane segments together, approximately how many amino acids are present in each of these loops, on the average