Hemoglobin O₂ dissociation curve
MCAT glossary · Biological & Biochemical Foundations of Living Systems
Definition
Sigmoidal cooperative binding; right shift (Bohr) by ↑CO_2, ↑H⁺, ↑temp, ↑2,3-BPG releases O_2; left shift retains O_2.
Hemoglobin O₂ dissociation curve in plain English
Hemoglobin is the protein in your red blood cells that grabs oxygen in your lungs and drops it off in your tissues. The clever part: it has four spots for oxygen, and once one oxygen locks on, it becomes EASIER for the next ones to attach — like the first person clapping making a whole crowd join in. That 'help each other' behavior gives the graph its S-shape (sigmoidal). When a tissue is working hard it gets hot, acidic, and full of CO_2 — those are exactly the signals that make hemoglobin loosen its grip and dump oxygen right where it's needed most (a 'right shift'); calm, cool conditions make it hold on (a 'left shift').
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