On average, how many amino acids engaged in predominantly hydrophobic α-helices does it take to cross the hydrophobic part of the membrane?

It will take up to 20-30 amino acids to cross the hydrophobic part of the membrane.

Explanation:

A helix is an element of protein structure that has two different side groups on both front and back.

In front, it has a hydrophilic and at the back, it has a hydrophobic group.

It will take averagely 20-30 amino acids to cross the hydrophobic part of the membrane.

The answer is 3.6 amino acids

Explanation:

The main chain of a polypeptide when folded in space adopts a conformation called helix ∝. In this structure each peptide bond establishes two hydrogen bonds. One of the hydrogen bonds is formed between the - NH - group of the amino acid peptide bond in position n and the - CO - group of the amino acid bond placed in position n-4. The second hydrogen bridge is formed between the group - CO - in position n and the group - NH - in position n + 4. Each turn of the helix is made up of 3.6 amino acids.