Most oxygen is transported in the blood bound to
alpha chains in hemoglobin
delta chains in hemoglobin
beta chains in hemoglobin
heme groups in hemoglobin
the plasma membrane of erythrocytes
The Correct Answer is D
A. alpha chains in hemoglobin: alpha chains are globin polypeptides that contribute to hemoglobin’s structure; O₂ binds to the heme prosthetic groups, not directly to the alpha globin chain.
B. delta chains in hemoglobin: delta chains (found in small amounts as HbA₂) are globin subunits; oxygen binding still occurs at heme groups, not the delta polypeptide.
C. beta chains in hemoglobin: beta chains are globin subunits that help form the O₂-binding pocket, but O₂ binds to the heme group (iron), not directly to the beta chain.
D. heme groups in hemoglobin: each hemoglobin has four heme groups (each with an Fe²⁺) that reversibly bind O₂; ~98–99% of blood O₂ is carried bound to hemoglobin’s heme.
E. the plasma membrane of erythrocytes: the RBC membrane does not bind O₂; O₂ diffuses across the membrane and is carried by hemoglobin inside the cell.
Nursing Test Bank
Naxlex Comprehensive Predictor Exams
Related Questions
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.
Correct Answer is C
Explanation
A. Granulocytes: granulocytes (neutrophils, eosinophils, basophils) are white blood cells that are part of the buffy coat.
B. Lymphocytes: lymphocytes (T cells, B cells, NK cells) are white blood cells found in the buffy coat.
C. Erythrocytes: erythrocytes (red blood cells) form the red cell layer below the buffy coat; the buffy coat contains white cells and platelets, not RBCs.
D. Agranulocytes: agranulocytes (lymphocytes and monocytes) are included in the buffy coat.
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