How many heme groups are there in each hemoglobin molecule?
1
2
3
4
The Correct Answer is E
A. 1: a single heme would carry one o₂, but adult hemoglobin contains more than one heme.
B. 0: hemoglobin contains heme groups (so zero is wrong).
C. 2: fetal hemoglobin and variants still have four heme groups per tetramer; two is not correct for a full hemoglobin molecule.
D. 3: hemoglobin has four globin chains and thus four heme groups, not three.
E. 4: each hemoglobin molecule has four heme groups (one per globin chain), so it can bind up to four o₂ molecules.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is D
Explanation
A. initiate blood clotting: Platelets and coagulation factors initiate clotting; erythrocytes do not initiate clot formation.
B. transport nutrients: Plasma carries most nutrients (glucose, amino acids, lipids), not erythrocytes.
C. defend the body against pathogens: White blood cells (leukocytes) are the main defenders; erythrocytes do not have immune functions.
D. transport some carbon dioxide: Erythrocytes carry a portion of CO₂ (dissolved as bicarbonate via carbonic anhydrase inside RBCs and also some carbaminohemoglobin).
E. regulate erythropoiesis: Erythropoiesis is regulated mainly by erythropoietin (from kidneys) and iron/nutritional signals, not by erythrocytes themselves.
Correct Answer is E
Explanation
A. 1: a single heme would carry one o₂, but adult hemoglobin contains more than one heme.
B. 0: hemoglobin contains heme groups (so zero is wrong).
C. 2: fetal hemoglobin and variants still have four heme groups per tetramer; two is not correct for a full hemoglobin molecule.
D. 3: hemoglobin has four globin chains and thus four heme groups, not three.
E. 4: each hemoglobin molecule has four heme groups (one per globin chain), so it can bind up to four o₂ molecules.
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