Final answer:
Amphiphilic helices are found in membrane proteins, particularly integral membrane proteins like transport proteins. They facilitate interaction with the lipid bilayer and aqueous environments, often forming channels for polar molecules and ions.
Step-by-step explanation:
Amphiphilic (or amphipathic) helices are characteristic of membrane proteins. These helices contain regions that are hydrophobic (water-repelling) and hydrophilic (water-attracting), allowing them to interact with both the fatty acid environment of the lipid bilayer and the aqueous environments inside and outside the cell. Integral membrane proteins, such as transport proteins, often contain one or more alpha-helices that span the lipid bilayer multiple times. These proteins can be involved in creating pores for the transport of polar molecules and ions. The hydrophobic alpha-helical regions anchor the proteins within the membrane, while the hydrophilic regions protrude into the cytosol or extracellular fluid to perform various functions, such as structural support, holding cells in place, and facilitating transport.