What are the functions of integral membrane proteins?

Integral polytopic proteins

Also known as transmembrane proteins, these types of integral proteins span the entire cell membrane. Some integral polytopic proteins cross the membrane only once (single-pass membrane proteins), while others weave in and out, crossing the membrane several times (multi-pass membrane proteins). Transmembrane proteins primarily function as gateways, enabling the transport of specific molecules and ions in and out of the membrane. When necessary, they may undergo conformational changes to transport a specific substance through the membrane. 

Integral monotropic proteins

Integral monotropic proteins do not span the lipid bilayer entirely. Instead they are permanently attached to the cell membrane only from one side. Receptors, transporters, structural membrane-anchoring domains, channels, enzymes, proteins responsible for cell adhesion and proteins involved in accumulation of transduction of energy are all integral monotropic proteins (IMPs). Integral monotropic proteins play a key role in cellular transport and signaling by facilitating the passage of specific molecules across the membrane and participating in various cellular communication processes.