Question

Identify the correct statement with reference to of respiratory gases by blood. (a) Haemoglobin is necessary for transport of dioxide and carbonic anhydrase for transeon axygen. (b) Haemoglobin is necessary for transport of onygin act carbonic anhydrase for transport of carbon dorite (c) Only oxygen is transported by blood. (d) Only carbon dioxide is transported by blood.

Short answer

The correct statement with reference to the transport of respiratory gases by blood is (b) Hemoglobin is necessary for transport of oxygen and carbonic anhydrase for transport of carbon dioxide.

Step-by-step solution

Understanding Respiratory Gas Transport

Respiratory gases such as oxygen (O2) and carbon dioxide (CO2) are transported by blood. Hemoglobin, contained in red blood cells, binds oxygen for transport. An enzyme called carbonic anhydrase helps convert CO2 into bicarbonate (HCO3-) for easier transport.

Evaluating the Options

Assess each statement for accuracy: (a) incorrectly states 'dioxide' and 'transeon axygen'. (b) correctly links hemoglobin to oxygen transport and carbonic anhydrase to carbon dioxide transport. (c) and (d) are incorrect because blood transports both oxygen and carbon dioxide.

Identifying the Correct Statement

Option (b) is the correct statement as it accurately pairs hemoglobin with the transport of oxygen and carbonic anhydrase with the transport of carbon dioxide.

Key concepts

Hemoglobin Function

Hemoglobin is a protein molecule found in red blood cells that is critical for transporting oxygen from the lungs to the rest of the body. Its structure allows it to bind to oxygen molecules in areas of high oxygen concentration, such as the lungs.

Each hemoglobin molecule is made up of four subunits, each containing an iron atom that can reversibly bind to an oxygen molecule. This binding is influenced by factors such as the pH and temperature of the blood—conditions that vary in different parts of the body. Understanding how hemoglobin works is crucial because it's the principal determinant of how oxygen is transported in the blood. Without hemoglobin, our ability to transport oxygen efficiently would be impaired, influencing our overall metabolic processes and health.

Oxygen Unloading and Affinity Changes

When red blood cells reach tissues with lower oxygen concentrations and higher carbon dioxide levels, hemoglobin releases oxygen, which is then used for cellular respiration. Additionally, hemoglobin has a cooperative binding, where the binding of each oxygen molecule to a subunit increases the affinity for the next oxygen molecule. Conversely, the release of one oxygen molecule decreases the affinity, facilitating oxygen unloading in tissues that need it the most.

Carbonic Anhydrase

Carbonic anhydrase is an enzyme found within red blood cells that catalyzes a critical reaction in the blood: the conversion of carbon dioxide and water into carbonic acid, which quickly dissociates into bicarbonate and a hydrogen ion.

This reaction is reversible and essential for carbon dioxide transport from the tissues back to the lungs. In tissues with high rates of metabolism, large quantities of carbon dioxide are produced. The carbonic anhydrase speeds up the conversion of carbon dioxide into bicarbonate, which can be transported in the blood plasma, freeing up the hemoglobin to pick up more oxygen.

Bicarbonate as a Buffer

Bicarbonate also serves as an important buffer, helping to maintain the pH balance in blood. The formation of bicarbonate from carbon dioxide allows for the efficient removal of excess CO2, which is crucial since CO2 can directly influence the pH of blood due to its ability to form carbonic acid.

Oxygen and Carbon Dioxide Transport

The transport of oxygen and carbon dioxide in the blood is a finely tuned process that addresses the body’s metabolic needs. Oxygen is primarily transported in the blood bound to hemoglobin in the red blood cells. Upon reaching tissues that have utilized oxygen, hemoglobin releases oxygen where it's then used for energy production.

Conversely, carbon dioxide, a waste product of metabolism, is transported from tissues back to the lungs. A small portion of it dissolves directly into the blood plasma, but the majority is converted into bicarbonate by carbonic anhydrase within red blood cells.

Coordination of Transport

The coordination between hemoglobin-bound oxygen and bicarbonate-bound carbon dioxide is known as the Bohr effect. An increase in carbon dioxide and hydrogen ions in the blood decreases hemoglobin's affinity for oxygen, enhancing oxygen unloading in tissues. This interdependence ensures that oxygen delivery and carbon dioxide removal are synchronized to the body's needs, maintaining homeostasis and optimizing respiratory efficiency.