MCAT® ExamBiological and Biochemical Foundations of Living SystemsHard
A patient experiences chronic fatigue, difficulty concentrating, and impaired immune function. Blood tests reveal abnormally low levels of transferrin, a protein responsible for iron transport in the bloodstream. This deficiency would most directly impair which of the following physiological processes?
- AGlucose metabolism in red blood cells
- BSynthesis of steroid hormones
- COxygen transport by hemoglobin
- DAbsorption of water in the large intestine
Show answer & explanationAnswer & explanation
Correct answer: C. Oxygen transport by hemoglobin
Iron is a critical component of the heme group in hemoglobin, which is essential for oxygen binding and transport in red blood cells. Low transferrin (iron transport protein) leads to iron deficiency, directly impairing hemoglobin synthesis and thus oxygen transport.
Why the other options are wrong
- A. Glucose metabolism in red blood cells (glycolysis) does not directly require iron.
- B. Steroid hormone synthesis occurs in the adrenal glands and gonads and is derived from cholesterol, not directly dependent on iron transport.
- D. Water absorption in the large intestine is primarily osmotic and does not directly rely on transferrin or iron.
Iron's Role in Oxygen Transport
Iron is an essential mineral that is a central component of the heme group in hemoglobin, the protein responsible for binding and transporting oxygen in the blood.
- Transferrin transports iron in the bloodstream.
- Iron deficiency leads to anemia (reduced oxygen-carrying capacity).
- Crucial for cellular respiration enzymes as well.
Memory trick: Iron's role: Oxygen, Energy, Immunity.