Concept 28.3

Question:
I. How is Trypanosoma's ability to produce an array of cell-surface proteins advantageous to its survival?

Answers:
a) The surface of a trypanosome is coated with millions and millions of copies of a single protein. Before, a host's immune system could mount an attack, new generations of the parasite switch to another surface protein with a slightly different molecular structure. Frequent changes in the structure of the surface of the protein prevent the host from developing immunity, thus contributing to its (Trypanosoma) survival.
b) The proteins have slightly different structures, but only one protein at a time is expressed. Frequent changes in expression prevent the host from developing immunity.

Question:
II. Is Euglena an alga? Explain your answer.

Answer:
a) Euglena could be considered an alga because it is a photosynthetic autotroph; however, it could also be considered a fungus-like protist because it can absorb organic nutrients from its environment.