28. Explain what happens when a B cell first encounters a pathogen and binds to an antigen on the pathogen. 1. What is the function of a memory cell? 2. What is the structure of hemoglobin? Which part...

28. Explain what happens when a B cell first encounters a pathogen and binds to an antigen on the pathogen.

1. What is the function of a memory cell?

2. What is the structure of hemoglobin? Which part of the hemoglobin molecule binds to oxygen?

3. How many oxygen molecules can one molecule of hemoglobin carry?