What appears to serve as "fences" around portions of the membrane that restrict the distance an integral protein can travel?

How can antibodies "remember" a particular bacterial invader or "antigen" on that invader?

Is there any species that went extinct in recent years due to natural causes (not caused by human interaction). if so, what caused it?

If jane has the blood type ab and marries john who has type o blood what are the possible phenotypes of their first kid?