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 A
Explanation
A. Cortisol: Cortisol (a glucocorticoid from the adrenal cortex) dominates the resistance stage of the general adaptation syndrome by sustaining energy supplies (gluconeogenesis), mobilizing fats/proteins, and modulating immune/inflammatory responses during prolonged stress.
B. Aldosterone: Aldosterone (a mineralocorticoid) contributes to long-term fluid and electrolyte adjustments by promoting Na⁺ and water retention, but the principal hormone of the resistance stage is cortisol.
C. Epinephrine: Epinephrine (from the adrenal medulla) mediates the alarm or immediate fight-or-flight response (rapid, short-term effects), not the sustained resistance stage.
D. Angiotensin: Angiotensin II is part of the RAAS and raises blood pressure/stimulates aldosterone, but it is not the dominant hormone of the resistance stage.
E. Norepinephrine: Norepinephrine is a sympathetic neurotransmitter/mediator of the immediate alarm response; it is not the main hormone in the prolonged resistance phase.
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.
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