T-helper cells have a molecule known as on their surface that enables them to respond to the targeted antigen. It is important to note that, in a reverse of the normal process, the Human Immunodeficiency Virus (HIV) attacks the T cells, which can then lead to an eventual compromise of the immune system against opportunistic infections.

How does pregnancy begin? a) a placenta forms in the uterus b) a sperm reaches an egg in the fallopian tubec) the blastocyst differentiates into two cell types d) contractions begin in the uterine wallapex

Which group of algae is characterized by unicellular organisms and includes some members that would be better classified as zooflagellates? euglenophytes red algae sporozoans green algae

Can bacteria reproduce in a way such that when you start out with two bacteria, you get five bacteria? why or why not? * a. yes, because bacteria reproduce sexually, and can produce any number of offspring, just as humans do. b. no, because bacteria grow at an exponential rate. c. no, because when bacteria reproduce, they split into two parts, and two bacteria splitting would result in four bacteria.