Oxygen
The spark of cellular life. Oxygen is essential for aerobic respiration—the process that generates most of our ATP. It's the final electron acceptor in the mitochondrial electron transport chain. But oxygen doesn't work alone: hemoglobin carries it, CO2 helps release it to tissues, and iron binds it. Understanding oxygen delivery explains why iron deficiency causes fatigue.
The Oxygen Journey
Inhalation
Air enters lungs. 21% oxygen. Reaches alveoli. 300 million air sacs.
Diffusion
O2 crosses alveolar membrane. Into capillary blood. Passive process. Follows gradient.
Hemoglobin Binding
O2 binds heme iron. 4 O2 per hemoglobin. Cooperative binding. Color changes.
Circulation
Heart pumps oxygenated blood. Travels via arteries. Reaches every tissue.
Release (Bohr Effect)
CO2 and acid help release O2. Active tissues get more. Elegant delivery.
Mitochondrial Use
Final electron acceptor. Creates water. Enables ATP synthesis. 36 ATP per glucose.
Factors in Oxygen Delivery
Hemoglobin Levels
More hemoglobin = more O2 capacity. Anemia reduces delivery. Iron critical.
Blood Flow
Heart output matters. Circulation health. Nitric oxide dilates vessels.
CO2 Levels
Need adequate CO2 for O2 release. Overbreathing impairs delivery paradoxically.
pH
Acidic helps O2 release. Alkaline holds it on. Exercise produces acid locally.
2,3-DPG
Red blood cell molecule. Shifts O2 release. Adapts to altitude, anemia.
Mitochondrial Health
Final destination. Damaged mitochondria can't use O2. CoQ10, NAD+ needed.
Low Oxygen Causes
Anemia
Not enough hemoglobin. Iron, B12, folate issues. Most common cause of low delivery.
Lung Disease
COPD, pulmonary fibrosis. O2 can't get into blood. SpO2 drops.
Sleep Apnea
Breathing stops during sleep. Repeated O2 drops. Cardiovascular stress.
Heart Failure
Pump can't deliver. Tissues hypoxic. O2 in blood but not reaching cells.
Carbon Monoxide
Binds hemoglobin 250x stronger. Displaces O2. Silent killer.
Altitude
Less O2 in thin air. Body adapts over time. EPO increases red cells.