Question

Factors at tissue level favours the dissociation of oxygen from oxyhaemoglobin (a) Low \(\mathrm{pO}_{2}\), low \(\mathrm{pCO}_{2}\), high \(\mathrm{H}^{+}\), low temperature (b) High \(\mathrm{pO}_{2}\), high \(\mathrm{pCO}_{2}\), low \(\mathrm{H}^{+}\), high temperature (c) Low \(\mathrm{pO}_{2}\), high \(\mathrm{pCO}_{2}\), high \(\mathrm{H}^{+}\), high temperature (d) Low \(\mathrm{pO}_{2}\), high \(\mathrm{pCO}_{2}\), high \(\mathrm{H}^{+}\), low temperature

Short answer

The conditions that most favor the dissociation of oxygen from oxyhaemoglobin at the tissue level are found in option (c): low \(\mathrm{pO}_{2}\), high \(\mathrm{pCO}_{2}\), high \(\mathrm{H}^{+}\), and high temperature.

Step-by-step solution

Understanding the conditions that favor oxygen's dissociation from hemoglobin

The dissociation of oxygen from hemoglobin—turning oxyhemoglobin into hemoglobin and oxygen—is increased when: 1) the partial pressure of oxygen (\(\mathrm{pO}_{2}\)) is low,2) the partial pressure of carbon dioxide (\(\mathrm{pCO}_{2}\)) is high, 3) the concentration of hydrogen ions (\(\mathrm{H}^{+}\)) is high, 4) the temperature is high. These conditions, often found in vigorously respiring tissues, ensure that oxygen is delivered where it's needed most.

Applying the Bohr effect conditions to each given option

Now, these conditions can be applied to the given options to see which option best fulfills the most conditions favoring oxygen's dissociation from hemoglobin: (a) The low \(\mathrm{pO}_{2}\) and high \(\mathrm{H}^{+}\) favor dissociation, but the low \(\mathrm{pCO}_{2}\) and low temperature do not. (b) The high \(\mathrm{pCO}_{2}\) and high temperature favor dissociation, but the high \(\mathrm{pO}_{2}\) and low \(\mathrm{H}^{+}\) do not.(c) The low \(\mathrm{pO}_{2}\), high \(\mathrm{pCO}_{2}\), high \(\mathrm{H}^{+}\), and high temperature all favor dissociation. (d) The low \(\mathrm{pO}_{2}\), high \(\mathrm{pCO}_{2}\), and high \(\mathrm{H}^{+}\) favor dissociation, but the low temperature does not.

Determining the best set of conditions

Considering each option, it's clear that option (c) best meets all the conditions that favor the dissociation of oxygen from hemoglobin: the \(\mathrm{pO}_{2}\) is low, the \(\mathrm{pCO}_{2}\) and \(\mathrm{H}^{+}\) concentrations are high, and the temperature is high.

Key concepts

Oxyhaemoglobin

Oxyhaemoglobin is a complex formed when oxygen binds to hemoglobin in the blood. This occurs in the lungs where there is high oxygen concentration. Hemoglobin is a protein in red blood cells responsible for transporting oxygen from the lungs to the tissues.

Two alpha and two beta chains make up its structure, each containing a heme group that can bind to one oxygen molecule. When all heme sites are occupied by oxygen, it is considered fully saturated, leading to the formation of oxyhaemoglobin.

The efficiency of oxygen transportation largely depends on the ability to form and dissociate oxyhaemoglobin quickly. Without this capability, tissues would not receive the oxygen required to perform vital metabolic functions. Understanding oxyhaemoglobin's role is crucial for comprehending the processes underpinning cellular respiration and the Bohr effect.

Oxygen Dissociation

Oxygen dissociation refers to the release of oxygen from oxyhaemoglobin, allowing it to enter tissues that need it. This process is vital in delivering oxygen to cells, especially those with high energy demands.

When tissues respire vigorously, they consume oxygen quickly, reducing their oxygen pressure, or \( \mathrm{pO}_{2} \). Additionally, they produce carbon dioxide and hydrogen ions, which alter the blood pH. These conditions facilitate the dissociation of oxygen from oxyhaemoglobin. This phenomenon is explained by the Bohr effect, where certain factors like increased \( \mathrm{H}^{+} \) and CO2 concentrations enhance oxygen release.

Understanding how oxygen dissociation works helps us grasp how the body adapts to continuous changes in oxygen demand and supply, crucial for maintaining metabolic balance.

Partial Pressure of Gases

Partial pressure is a term used to describe the concentration or availability of a specific gas within a mixture. It's crucial in respiratory physiology because it governs the movement of gases such as oxygen and carbon dioxide in and out of the bloodstream.

The partial pressure of oxygen (\( \mathrm{pO}_{2} \)) and carbon dioxide (\( \mathrm{pCO}_{2} \)) are of particular interest. \( \mathrm{pO}_{2} \) is high in the lungs, where oxygen is abundant, encouraging oxygen binding to hemoglobin. Conversely, in metabolically active tissues, \( \mathrm{pO}_{2} \) is low, favoring oxygen dissociation from oxyhaemoglobin.

High \( \mathrm{pCO}_{2} \) levels in tissues indicate increased respiration and CO2 production. This enhances the Bohr effect, further aiding oxygen dissociation. By keeping track of these pressures, our body efficiently regulates respiration.

Vigorous Respiration

In conditions of vigorous respiration, the body increases its demand for oxygen. This scenario frequently occurs during intense physical activity or when tissues are under metabolic stress.

Tissues during vigorous respiration tend to have:

• Low oxygen pressures (\( \mathrm{pO}_{2} \)), due to high oxygen consumption.
• High carbon dioxide pressures (\( \mathrm{pCO}_{2} \)), as a result of increased carbon dioxide production.
• Increased hydrogen ion concentration (\( \mathrm{H}^{+} \)), leading to decreased pH.

The Bohr effect plays a crucial role here by aiding the release of oxygen from oxyhaemoglobin to supply the demanding tissues. Understanding how and why vigorous respiration affects gas exchange is key to comprehending both respiratory and cardiovascular adaptations to physical activity.

Temperature Influence

Temperature is a significant factor influencing the oxygen dissociation curve. In general, as temperature increases, hemoglobin's affinity for oxygen decreases.

This means at higher temperatures, hemoglobin releases oxygen more readily, facilitating greater oxygen supply to actively respiring tissues.

Physiologically, elevated temperatures might occur during fever or strenuous physical exertion. In these cases, increased temperature helps meet the heightened oxygen demand by enhancing oxygen dissociation.

Thus, temperature is another factor that modulates how our bodies efficiently deliver oxygen during times of increased metabolic activity, ensuring optimal performance of metabolic processes.