Biological Systems MCAT Practice Exam 2026 – The Comprehensive All-in-One Guide for Exam Success!

An increase in carbon dioxide concentration decreases hemoglobin's affinity for oxygen. This phenomenon occurs due to the Bohr effect, where increased levels of carbon dioxide and the corresponding drop in pH (due to the formation of carbonic acid) lead to a conformational change in hemoglobin. This change makes it less able to bind oxygen, facilitating the release of oxygen in tissues that are actively metabolizing and producing carbon dioxide. The decrease in affinity ensures that tissues with high levels of carbon dioxide can receive the oxygen they need for aerobic respiration.

This understanding is critical because it illustrates the dynamic relationship between carbon dioxide levels and oxygen delivery in the body, highlighting how metabolic activity can influence gas exchange.