Final answer:
Integral membrane protein transmembrane segments are typically α-helical structures of about 20-30 amino acids composed mainly of hydrophobic amino acids and are not amphipathic.
Step-by-step explanation:
A typical characteristic of an integral membrane protein transmembrane segment that does NOT apply is (D) amphipathic. Although integral membrane proteins often have hydrophilic regions, the transmembrane segments themselves are primarily characterized by being:
- (A) α-helical structure
- (B) Approximately 20-30 amino acids long
- (C) Composed primarily of hydrophobic amino acids
Integral proteins are embedded within the cell membrane and have transmembrane domains that are hydrophobic, aligning with the lipid bilayer's hydrophobic tails. The transmembrane regions are typically not amphipathic; instead, regions of the protein that protrude from the membrane may be amphipathic, interacting with the aqueous environment inside or outside the cell.