What characteristics of the peptide chain allow the integral membrane to "stick in the membrane?

What characteristics of the peptide chain allow the integral membrane to "stick in the membrane? 

Almost all protein complexes are assembled outside the nucleus in various cytoplasmic compartments. An exception to this is the ribosome, which is built inside the nucleus. Where are ribosomal proteins translated (circle one)?

inside the nucleus                          outside the nucleus

Examine the following structure and label the asymmetric carbons, if any.