Question

the chemical structures of indole and tryptophan are very similar. based on chemical structure, why is the membrane less permeable to tryptophan than indole? select all that apply. indole has fewer polar covalent bonds than tryptophan. tryptophan is a larger molecule than indole. indole has only nonpolar covalent bonds whereas tryptophan has only polar covalent bonds. tryptophan has two full charges whereas indole is neutral.

Explanation:

• Indole has fewer polar covalent bonds than tryptophan: Polar covalent bonds make a molecule more hydrophilic. Since cell membranes are made of a lipid bilayer (hydrophobic core), molecules with more polar bonds (like tryptophan) have a harder time crossing the membrane compared to molecules with fewer polar bonds (indole).
• Tryptophan is a larger molecule than indole: Larger molecules generally have more difficulty diffusing through the lipid - bilayer membrane. The membrane's hydrophobic core restricts the passage of larger molecules more than smaller ones.

• Indole has only non - polar covalent bonds whereas tryptophan has only polar covalent bonds: This is incorrect. Indole has some polar covalent bonds (e.g., \(C - N\) bond). Tryptophan also has non - polar regions (the aromatic ring part).
• Tryptophan has two full charges whereas indole is neutral: Tryptophan does not have two full charges in its typical form. It has a zwitterion form in aqueous solution (a positive charge on the amino group and a negative charge on the carboxyl group at physiological pH), but it is not a molecule with two full charges in the sense of being a highly charged species like an ion pair. And indole is neutral, but the charge - related issue is not the main reason as described in this option.

Answer:

Indole has fewer polar covalent bonds than tryptophan, Tryptophan is a larger molecule than indole.