The teacher warning could be the practice you are about to do can harm you in some way if that careful. Please let me know if I'm understanding this.
Freshwater means low salt content. The zones namely Standing which is compose of ponds and lakes and has littoral zone which algae,floating aquatic plants and clams can be found. Next is limnetic zone and has plankton. Next is Flowing includes streams and rivers and in there resides catfish and carp. For sea water it has Marine which has aphotic zone where anemones,arrow worm and angler fish resides.Another, coastal zone compose of coral reefs and mangrove and lastly the intertidal zone with small critters.
The correct answer is: They usually have one or more helical regions spanning the membrane bilayer
Transmembrane proteins are type of integral proteins meaning that they are permanently attached to biological membrane. Transmembrane proteins span through the plasma membrane so most of their structure is hydrophobic.
The major role of these proteins is transport role: they act as a channels that undergo conformational change in order to move a substance through the membrane.
Classified by their structure they can be put into two types: alpha helical and beta barrels.