On average, how many amino acids, forming a hydrophobic $\alpha$-helix, does it take to cross the hydrophobic part of the membrane?
A)about 10 amino acids
B)about 20 amino acids
C)at least 40 amino acids
D)about 2-3 amino acids
E)None of these are correct.

Question

Quizplus · Accepted Answer

It takes about 20 amino acids to form a hydrophobic α-helix that can cross the hydrophobic part of the membrane. This is because the hydrophobic core of the membrane is about 30 Angstroms thick, and a typical amino acid side chain is about 4-5 Angstroms wide. Therefore, it takes about 6-7 amino acids to span one side of the membrane, so a helix would need about 20 amino acids to span the entire hydrophobic core.

On Average, How Many Amino Acids, Forming a Hydrophobic α\alphaα -Helix, Does It Take to Cross the Hydrophobic Part of -Helix

On Average, How Many Amino Acids, Forming a Hydrophobic $\alpha$ -Helix, Does It Take to Cross the Hydrophobic Part of -Helix