Oxygen Hemoglobin Dissociation Curve | Oxygen transport | Gas Exchange | Respiratory Physiology

Summary

This video explains the oxygen-hemoglobin dissociation curve, illustrating how oxygen binds to hemoglobin and is transported from the alveoli to tissues. It covers key concepts like positive cooperativity, the Bohr effect, and factors that shift the dissociation curve, such as pH, carbon dioxide, temperature, and 2-3 DPG. The video also compares adult and fetal hemoglobin, highlighting their different oxygen affinities. Overall, it emphasizes the mechanisms that enable efficient oxygen delivery to tissues under various conditions, such as exercise or high altitude.

Takeaways

• 😀 The main purpose of respiration is gas exchange, where oxygen enters the blood and carbon dioxide is removed.
• 😀 Oxygen is carried in the blood both dissolved (2%) and bound to hemoglobin (98%), with only dissolved oxygen contributing to partial pressure.
• 😀 The oxygen binding to hemoglobin is reversible, and when all four oxygen molecules are bound, hemoglobin is 100% saturated.
• 😀 Hemoglobin’s affinity for oxygen changes with each molecule bound due to positive cooperativity, making the oxygen-hemoglobin dissociation curve sigmoidal (S-shaped).
• 😀 The P50 is the partial pressure of oxygen at which hemoglobin is 50% saturated, and it shifts depending on oxygen affinity.
• 😀 A shift to the right in the curve (lower affinity) means more oxygen is released to tissues, which occurs during high CO2, low pH, increased temperature, or high 2,3-DPG.
• 😀 A shift to the left in the curve (higher affinity) means less oxygen is released, occurring in low CO2, high pH, low temperature, low 2,3-DPG, or in fetal hemoglobin.
• 😀 The Bohr effect describes how increased CO2 and lower pH decrease hemoglobin’s affinity for oxygen, promoting oxygen release to tissues.
• 😀 In high-altitude or hypoxic conditions, increased production of 2,3-DPG helps hemoglobin release more oxygen to tissues.
• 😀 Fetal hemoglobin has a higher affinity for oxygen than adult hemoglobin due to its different subunit composition, allowing for efficient oxygen transfer from the mother.

Q & A

What are the two primary ways oxygen is transported in the blood?

Oxygen is transported in the blood in two forms: as dissolved oxygen (about 2% of total oxygen) and as oxygen bound to hemoglobin (98%).

Why does only dissolved oxygen contribute to the partial pressure of oxygen?

Dissolved oxygen contributes to the partial pressure of oxygen because bound oxygen, which is attached to hemoglobin, does not exert a partial pressure.

How does the oxygen-hemoglobin dissociation curve change in response to positive cooperativity?

The oxygen-hemoglobin dissociation curve is sigmoidal due to positive cooperativity, where the binding of one oxygen molecule to hemoglobin increases the affinity of hemoglobin for subsequent oxygen molecules.

What is the P50 and how does it relate to the affinity of hemoglobin for oxygen?

P50 is the partial pressure of oxygen at which hemoglobin is 50% saturated with oxygen. If P50 increases, the affinity of hemoglobin for oxygen decreases, and if P50 decreases, the affinity increases.

What physiological conditions can shift the oxygen-hemoglobin dissociation curve to the right?

Conditions that shift the curve to the right (lower affinity) include increased partial pressure of carbon dioxide, lower pH (such as during exercise), higher temperatures, higher 2,3 DPG, and hypoxia (like at high altitudes).

How does the Bohr effect influence the oxygen-hemoglobin dissociation curve?

The Bohr effect refers to how increased carbon dioxide or hydrogen ion concentration (lower pH) reduces hemoglobin’s affinity for oxygen, promoting oxygen release to tissues in need.

How does temperature affect the oxygen-hemoglobin dissociation curve?

Higher temperatures cause a rightward shift in the curve, decreasing hemoglobin’s affinity for oxygen, which enhances oxygen unloading to tissues with increased metabolic activity.

Why does fetal hemoglobin have a higher affinity for oxygen than adult hemoglobin?

Fetal hemoglobin has a higher affinity for oxygen because it has gamma chains instead of beta chains. These gamma chains reduce the binding of 2,3 DPG, which increases the affinity for oxygen.

What role does 2,3 DPG play in the oxygen-hemoglobin dissociation curve?

2,3 DPG binds to hemoglobin, reducing its affinity for oxygen. High levels of 2,3 DPG shift the curve to the right, facilitating oxygen release to tissues.

How does the oxygen-hemoglobin dissociation curve help in oxygen delivery to tissues during exercise?

During exercise, increased levels of CO2, lactic acid, and temperature shift the curve to the right, lowering hemoglobin’s affinity for oxygen and ensuring more oxygen is delivered to active muscles.