Problem 40 - Objective Biology for NEET

Question

What is the total gain of energy during anaerobic respiration? (a) One molecule of ATP (b) Two molecules of ATP (c) Four molecules of ATP (d) Eight molecules of ATP

Step-by-Step Solution

Answer

The total gain of energy during anaerobic respiration is two molecules of ATP. Therefore, the correct option is (b) Two molecules of ATP.

Step 1: Anaerobic Respiration

Anaerobic respiration is the process by which cells produce energy without the presence of oxygen. This often happens when the demand for oxygen from the body is greater than the supply, such as during intensive physical exercise.

Step 2: ATP Production

The end product of anaerobic respiration is ATP (Adenosine Triphosphate). ATP is considered as the energy currency of the cell, so it's production is crucial for the cell's energy needs.

Step 3: Amount of ATP generated

During anaerobic respiration specifically, a net gain of two ATP molecules is generated per glucose molecule. This is less efficient than aerobic respiration, which generates approximately 36 ATP molecules per glucose molecule.

Key Concepts

ATP Production

Adenosine Triphosphate, commonly known as ATP, is the main energy carrier in all living organisms. During anaerobic respiration, which occurs in the absence of oxygen, cells convert glucose into energy in the form of ATP. This process is particularly important in muscle cells during vigorous exercise when there isn't enough oxygen available.

The total yield of ATP per glucose molecule through anaerobic respiration is relatively low, with only two molecules of ATP produced. This is in stark contrast to the 36 or more molecules yielded during aerobic respiration, which uses oxygen.

Despite its lower efficiency, the rapid production of ATP through anaerobic means ensures that cells can continue to function during short-term, high-intensity activities. It's crucial because it provides immediate energy and allows the organism to survive until a more efficient oxygen-based energy production can resume.

Cellular Respiration

Cellular respiration is a vital process through which cells extract energy from nutrients. It can be aerobic, utilizing oxygen, or anaerobic, which does not require oxygen.

Anaerobic respiration typically occurs in environments low in oxygen, such as in muscle cells under intense workout conditions, when the oxygen supply can't meet the demand. The process begins with glycolysis, where glucose is partially broken down, yielding two ATP molecules and two molecules of pyruvate.

Since there's no oxygen, the pyruvate undergoes fermentation to replenish the necessary co-factors for glycolysis to continue. The simplicity of this process allows ATP to be generated quickly, even though it's not as much as what is obtained from aerobic respiration. The minimal gain, however, is enough to sustain energy requirements for a short duration under anaerobic conditions.

Energy Metabolism

Energy metabolism encompasses all the biochemical processes that occur in living organisms to produce and use energy. These reactions are tightly regulated and highly efficient, ensuring that cells have a consistent energy supply to perform various functions.

During anaerobic respiration, the energy metabolism shifts from an oxygen-dependent mode to an oxygen-independent pathway. As such, the breakdown of glucose via glycolysis and subsequent fermentation is a central adaptative mechanism during oxygen-limited conditions.

While this form of metabolism isn't sustainable for long periods (due to the low yield of ATP and the accumulation of byproducts like lactate), it serves as a critical stopgap that supports life during transient periods when oxygen levels drop precipitously. Students should appreciate how different pathways of energy metabolism interact and compensate to maintain energy flow within cells, despite varying environmental conditions.