?

AP® Biology

Free Version

Upgrade subject to access all content

Difficult

Dissolved Oxygen Levels in Athletes

APBIO-HWTNEJ

A high school track athlete approaches her coach to report that training sessions feel much more difficult than before. Also, her times for the 800-meter sprint are getting worse, and she seems to get out of breath easily. The coach suggests a visit to a doctor.

During the doctor’s visit, the nurse finds that the girl has very low blood oxygen saturation levels, despite having a slightly rapid breathing rate. A quick test shows that the girl has severe anemia (low blood iron levels).

How does this diagnosis explain the girl's low blood oxygen levels?

A

Iron is a cofactor required for hemoglobin proteins to bind oxygen in their active sites.

B

Iron is a buffer that prevents blood pH from acidifying, which denatures the oxygen-carrying protein hemoglobin.

C

Iron acts as a catalyst for the chemical reaction in which hemoglobin converts oxygen to carbonic acid.

D

Iron is a cofactor required by transport proteins embedded on the surface of muscle cells used to transport oxygen into body cells.