Oxygen and carbon dioxide bind to different parts of hemoglobin.

A. Prolactin (PRL): Prolactin is produced and secreted by the anterior pituitary (lactotrophs), not the posterior pituitary.
B. Thyroid hormone (TH): Thyroid hormones (T3/T4) are produced by the thyroid gland, not by the pituitary.
C. Adrenocorticotropic hormone (ACTH): ACTH is produced by the anterior pituitary (corticotrophs), not the posterior.
D. Growth hormone (GH): GH is secreted by the anterior pituitary (somatotrophs), not the posterior.
E. Oxytocin (OT): Oxytocin is synthesized in the hypothalamus and stored/released by the posterior pituitary

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.