Amino Acid Properties in Membrane Glycoproteins

Steps:

• Identify the alpha helix as spanning the hydrophobic lipid bilayer, requiring non-polar amino acids for stability.
• Locate amino acid Q on the extracellular domain of the glycoprotein, exposed to aqueous environment.
• Classify alpha helix amino acids as non-polar due to hydrophobic interactions.
• Classify Q as polar to interact with water and support glycosylation.

Why A is correct:

• Non-polar for helix matches hydrophobic transmembrane requirement; polar for Q enables hydrophilic exposure per membrane protein structure.

Why the others are wrong:

• B: Q is polar, not non-polar, as it's surface-exposed.
• C: Helix amino acids are non-polar, not polar, to avoid bilayer repulsion.
• D: Helix is non-polar, not polar, for lipid compatibility.

Final answer: A