Problem 140 - Objective Biology for NEET

Question

Assertion: The maximum amount of \(\mathrm{CO}_{2}\) is converted into bicarbonate ion in RBCs. Reason: RBCs contain a very high concentration of the enzyme, carbonic anhydrase.

Step-by-Step Solution

Answer

Both the assertion and the reason are true and the reason correctly explains the assertion. The presence of the enzyme, carbonic anhydrase in large amounts in Red Blood Cells significantly facilitates in converting the maximum amount of \(\mathrm{CO}_{2}\) into bicarbonate ions.

Step 1: Understanding the Roles

First, understand what each component does. \(\mathrm{CO}_{2}\) is an end product of cellular respiration, which needs to be transported out of the body. The bicarbonate ion (\(\mathrm{HCO}_{3}^{-}\)) is one way \(\mathrm{CO}_{2}\) is transported in the blood. Red Blood Cells (RBCs), particularly contain enzymes such as carbonic anhydrase which facilitate this conversion.

Step 2: Analyzing the Assertion

Secondly, analyze the assertion given. The assertion is that the maximum amount of offloaded \(\mathrm{CO}_{2}\) is converted into bicarbonate ion in RBCs. Based on general cellular biology knowledge, we know that this is true. The presence of the enzyme carbonic anhydrase in RBCs allows the reaction \(\mathrm{CO}_{2}\) + \(\mathrm{H}_{2}\mathrm{O}\) \(\longrightarrow\) \(\mathrm{H}_{2}\mathrm{CO}_{3}\) \(\longrightarrow\) \(\mathrm{HCO}_{3}^{-}\) + \(\mathrm{H}^{+}\) to occur, thereby facilitating the conversion of \(\mathrm{CO}_{2}\) into bicarbonate ions.

Step 3: Analyzing the Reason

Thirdly, analyze the reason given. The reason stated is that RBCs contain a very high concentration of the enzyme, carbonic anhydrase. This is also true. RBCs do contain a high concentration of carbonic anhydrase which speeds up the reaction that converts \(\mathrm{CO}_{2}\) into bicarbonate ions.

Step 4: Interrelating Assertion and Reason

Lastly, establish if the reason explains the assertion or not. In this case, the reason is directly related to the assertion as the high concentration of carbonic anhydrase in RBCs is what allows for the rapid conversion of \(\mathrm{CO}_{2}\) into bicarbonate ions. Hence, the reason correctly explains the assertion.

Key Concepts

Bicarbonate Ion

Bicarbonate ions (\(\mathrm{HCO}_{3}^{-} \)) play a vital role in the body's ability to transport carbon dioxide (\(\mathrm{CO}_{2} \)) from tissues to the lungs. As cells go about their daily activities, they produce \(\mathrm{CO}_{2} \) as a waste product. To be expelled from the body, \(\mathrm{CO}_{2} \) needs to travel through the bloodstream to the lungs. This is where bicarbonate ions come into the picture.

• When \(\mathrm{CO}_{2} \) enters the blood, it reacts with water (\(\mathrm{H}_{2}\mathrm{O} \)) to eventually form bicarbonate ions (\(\mathrm{HCO}_{3}^{-} \)) and hydrogen ions (\(\mathrm{H}^{+} \)).
• The reaction from \(\mathrm{CO}_{2} \) to bicarbonate is facilitated by enzymes, making it efficient.
• This conversion is essential as it allows \(\mathrm{CO}_{2} \) to be transported in a soluble form, enabling easy travel through the bloodstream.

Transportation of \(\mathrm{CO}_{2} \) in the form of bicarbonate ions is the most significant method, ensuring the body can handle cellular respiration products efficiently without disrupting the blood's pH balance.

Carbonic Anhydrase

Carbonic anhydrase is an enzyme crucial for the rapid conversion of carbon dioxide into bicarbonate ions. Located predominantly in red blood cells (RBCs), this enzyme accelerates the reaction tremendously, ensuring that the process happens quickly and efficiently.

• This enzyme facilitates the transformation of \(\mathrm{CO}_{2} \) and water into carbonic acid (\(\mathrm{H}_{2}\mathrm{CO}_{3} \)), a precursor to bicarbonate ions.
• Subsequently, carbonic acid dissociates into bicarbonate ions (\(\mathrm{HCO}_{3}^{-} \)) and hydrogen ions (\(\mathrm{H}^{+} \)).
• The presence of carbonic anhydrase in high concentrations within RBCs allows these reactions to proceed at an accelerated rate.

Purposely efficient, this means that even as \(\mathrm{CO}_{2} \) levels vary, the enzyme ensures steady conversion to maintain balance. Without carbonic anhydrase, the body would struggle to process \(\mathrm{CO}_{2} \) effectively, leading to possible accumulation and subsequent issues.

Red Blood Cells

Red blood cells (RBCs) are not only responsible for carrying oxygen but also play a critical role in transporting carbon dioxide. Within these cells, carbonic anhydrase acts to catalyze important reactions necessary for \(\mathrm{CO}_{2} \) transport.

• RBCs have specialized structures without a nucleus, giving more space to maximize hemoglobin and enzymes like carbonic anhydrase.
• Inside RBCs, carbonic anhydrase rapidly converts \(\mathrm{CO}_{2} \) into bicarbonate ions, facilitating more efficient transport in the blood.
• The processed bicarbonate ions can diffuse out of the RBCs into the plasma, providing a way for \(\mathrm{CO}_{2} \) to be carried effectively to the lungs.

The dual role of RBCs in gas transport showcases their importance in maintaining respiratory efficiency. The efficient functioning of RBCs ensures that both oxygen delivery and carbon dioxide removal are seamless, keeping the body healthy and balanced.