Patient Case Study & Oxygen Dissociation Curve

The form of hemoglobin when oxygen is bound to it. This form is referred to as the relaxed state due to its high affinity for oxygen.

The form of hemoglobin when oxygen is not bound to it. This form is referred to as the tense state due to its lower affinity for oxygen.

Hemoglobin's ability to bind more oxygen as more oxygen molecules become bound. The binding of the first oxygen molecule makes it easier for subsequent oxygen molecules to bind.

The steep upward curve of the oxygen dissociation curve represents the high affinity for oxygen after the first molecule binds. This means it becomes easier for each subsequent oxygen molecule to bind to hemoglobin.

The partial pressure of oxygen in the lungs is about 100 mm Hg, while in the tissues it is about 40 mm Hg. This difference in partial pressure drives the oxygen exchange.

A graphical representation of the relationship between the saturation of hemoglobin with oxygen and the partial pressure of oxygen. The higher the partial pressure of oxygen, the more oxygen is bound to hemoglobin.

Factors that can shift the oxygen dissociation curve to the right, decreasing hemoglobin's affinity for oxygen. This happens when the body needs to deliver more oxygen to tissues.

Factors that can shift the oxygen dissociation curve to the left, increasing hemoglobin's affinity for oxygen. This happens when the body needs to conserve oxygen.

2,3-Bisphosphoglycerate (2,3-BPG) is a molecule found in red blood cells. It binds to hemoglobin, reducing its affinity for oxygen and causing the oxygen dissociation curve to shift to the right. This means hemoglobin releases oxygen more readily in tissues.

Chronic hypoxia or anemia triggers an increase in 2,3-BPG levels. This helps deliver more oxygen to tissues by promoting oxygen release from hemoglobin.

Carbaminohemoglobin is formed when carbon dioxide binds to hemoglobin. This is a minor way carbon dioxide is transported in the blood.

Increasing temperature weakens the bond between oxygen and hemoglobin, causing a rightward shift in the oxygen dissociation curve. This means hemoglobin releases oxygen more readily at higher temperatures.

Carbon monoxide binds to hemoglobin with much greater affinity than oxygen, forming carboxyhemoglobin. This reduces hemoglobin's oxygen-carrying capacity and affects its ability to release oxygen.

Sulfhemoglobin forms when sulfur reacts with hemoglobin, blocking its oxygen-carrying capacity. This is an irreversible reaction caused by high sulfur levels in blood.

Methemoglobin is formed when the iron in hemoglobin is oxidized from Fe⁺⁺ to Fe+++. This form of hemoglobin cannot bind oxygen, reducing its ability to carry oxygen in the blood.

The body has mechanisms to convert Methemoglobin back to functional hemoglobin. NADH Methemoglobin reductase is a key enzyme in this process.

The ability of hemoglobin (Hb) to bind oxygen is affected by several factors, including the partial pressure of oxygen (pO2), pH, partial pressure of carbon dioxide (pCO2), and the presence of 2,3-bisphosphoglycerate (2,3-BPG). These factors are known as allosteric effectors.

Oxygen (O2) is a positive allosteric effector, meaning it increases hemoglobin's affinity for oxygen. As more oxygen molecules bind to hemoglobin, the affinity for subsequent oxygen molecules increases.

Hydrogen ions (H+) are negative allosteric effectors. Increased acidity in the environment (lower pH) reduces hemoglobin's affinity for oxygen. This is known as the Bohr effect. Elevated carbon dioxide (CO2) levels can also lead to an increase in acidity, contributing to the Bohr effect.

2,3-bisphosphoglycerate (2,3-BPG) is an intermediate compound in glycolysis. It is a negative allosteric effector that decreases hemoglobin's affinity for oxygen, which is useful under conditions of low oxygen levels (hypoxia) because it facilitates the unloading of oxygen to tissues.

Allosteric effectors can shift the oxygen dissociation curve (ODC) to the right or left. A right shift indicates lower hemoglobin affinity for oxygen, while a left shift indicates higher affinity.

The Bohr effect refers to the lower affinity of hemoglobin for oxygen in the presence of higher partial pressure of carbon dioxide (pCO2) and/or lower blood pH. This shift to the right in the ODC helps facilitate unloading of oxygen to tissues, especially during metabolically active periods when there is increased CO2 production and lower pH.

Elevated 2,3-BPG levels are often found in conditions like chronic lung diseases, anemia, and high altitudes, where arterial blood is undersaturated with oxygen. 2,3-BPG lowers hemoglobin's affinity for oxygen, increasing oxygen delivery to tissues in these challenging environments.

The cooperative binding of oxygen to hemoglobin allows for more efficient oxygen delivery. Hemoglobin's structure changes with oxygen binding, making it easier for subsequent oxygen molecules to bind. This leads to a steeper upward curve in the oxygen dissociation curve, indicating the high affinity for oxygen after the first molecule binds.