Respiration. Part 2

Summary

The transcript explains the third stage of respiration, focusing on gas transport in the blood. Oxygen is carried in two forms: dissolved in water and bound to hemoglobin. The primary method is oxygen binding with hemoglobin to form oxyhemoglobin, which can carry up to four oxygen molecules. The oxyhemoglobin dissociation curve is discussed, showing how oxygen binds in the lungs and releases in tissues, influenced by partial oxygen pressure. The curve's S-shape reflects the cooperative interaction in hemoglobin, making oxygen binding easier as more molecules are attached.

Takeaways

• 🫁 The third stage of respiration involves the transport of gases, specifically oxygen and carbon dioxide, through the blood.
• 🧪 Oxygen is transported in two forms: dissolved in the blood (physically) and chemically bound to hemoglobin.
• 🧫 The amount of dissolved oxygen is relatively small, so the main method of oxygen transport is through oxyhemoglobin formation.
• 🩸 One hemoglobin molecule can carry up to four oxygen molecules, and this binding is cooperative, meaning each additional oxygen binds more easily.
• 📈 The direction of oxygen-hemoglobin binding and dissociation is explained by the oxyhemoglobin dissociation curve, which measures the partial pressure of oxygen.
• 💨 In the lungs, where oxygen pressure is high (about 100 mm Hg), hemoglobin binds oxygen to form oxyhemoglobin.
• 🏥 In tissues, where oxygen pressure is lower due to oxygen consumption by cells, oxygen is released from hemoglobin to be used by the cells.
• 📉 The oxyhemoglobin dissociation curve has an S-shape, which reflects the cooperative binding behavior of hemoglobin to oxygen.
• ⚖️ The curve never reaches 100% oxygen saturation because some hemoglobin always binds to carbon dioxide instead of oxygen.
• 🏃‍♂️ The right side of the curve represents oxygen binding in the lungs, while the left side shows oxygen release in tissues as hemoglobin dissociates from oxygen.

Q & A

What is the third stage of respiration described in the transcript?

The third stage of respiration is the transport of gases with the blood, specifically oxygen and carbon dioxide.

How is oxygen transported in the blood?

Oxygen is transported in two ways: 1) in a physically dissolved state, and 2) in chemical combination with hemoglobin to form oxyhemoglobin.

Why is the physically dissolved oxygen in blood considered less important?

The amount of dissolved oxygen is not very high, so it is not a significant method for oxygen transport in humans, although it is used by some animals like fish.

What is the predominant way of oxygen transport in the blood?

The predominant way of oxygen transport is in chemical combination with hemoglobin, forming oxyhemoglobin.

How many oxygen molecules can one molecule of hemoglobin carry?

One molecule of hemoglobin can carry up to four molecules of oxygen.

What factors determine whether hemoglobin binds to or releases oxygen?

The direction of the reaction between hemoglobin and oxygen is determined by the partial pressure of oxygen, which is illustrated by the oxyhemoglobin dissociation curve.

What is the oxyhemoglobin dissociation curve, and what does it represent?

The oxyhemoglobin dissociation curve is a graph that represents the relationship between the partial pressure of oxygen and the percentage of hemoglobin saturation with oxygen. It helps illustrate how oxygen is loaded in the lungs and released in the tissues.

Why does the oxyhemoglobin dissociation curve have an S-shape?

The S-shape of the curve is due to cooperative binding, where each oxygen molecule that binds to hemoglobin increases the likelihood of subsequent oxygen molecules binding, with the fourth oxygen binding most easily.

What does the right side of the dissociation curve represent?

The right side of the dissociation curve represents the situation in the lungs, where the partial pressure of oxygen is high, leading to the formation of oxyhemoglobin as hemoglobin binds oxygen.

What does the left side of the dissociation curve represent?

The left side of the curve represents the situation in tissues, where the partial pressure of oxygen is lower because tissues consume oxygen, causing hemoglobin to release oxygen.