Final answer:
The image from freeze fracture electron microscopy is likely showing a transmembrane protein with a hydrophobic alpha-helical domain, which indicates the structure's role in the plasma membrane and its integration within the lipid bilayer.
Step-by-step explanation:
When examining the structure of the plasma membrane using freeze fracture electron microscopy (E.M.), the student is likely observing a transmembrane protein. This technique reveals the mosaic organization and asymmetry of the plasma membrane and can show components like transmembrane domains. The picture taken from this technique that shows a 20 nonpolar amino acid sequence is indicative of a hydrophobic transmembrane segment, typically comprising an alpha-helix structure that spans the membrane. Such proteins are often involved in membrane transport, signalling, or as receptors, and their nonpolar sequences allow them to be embedded within the hydrophobic core of the lipid bilayer.
Furthermore, the oligosaccharides on glycoproteins and asymmetric distribution of proteins across the membrane can be deduced from such images. The transmembrane protein's orientation, with the N-terminal end usually exposed outside the cell, is determined during its synthesis, often involving a hydrophobic stop-transfer sequence that gets inserted into the membrane at the endoplasmic reticulum.