What is the pigment found in red algae

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

During the process of blank and molecules such as a glucose must use a protein channel to cross through a cell membrane

Which layer of the eye completely surrounds the eye except for a dark, round opening called the pupil? a. sclerab. corneac. retinad. choroidthe answer is a sclera