Question

How many ATP molecules are net gained during Glycolysis?

• A. 2 ATP
• B. 4 ATP
• C. 6 ATP
• D. 8 ATP

Hint:

In glycolysis:
ATP used = 2
ATP produced = 4
Net ATP gain = 2 ATP.

Answer 1

The Correct Option is A

Concept:
Glycolysis is the first step of cellular respiration and occurs in the cytoplasm of the cell. In this process, one molecule of glucose (a six-carbon compound) is broken down into two molecules of pyruvate (three-carbon compounds). Glycolysis does not require oxygen and therefore occurs in both aerobic and anaerobic conditions. During glycolysis, energy is released and captured in the form of ATP (adenosine triphosphate) and NADH molecules.

Step 1: ATP investment phase
At the beginning of glycolysis, the cell must invest energy to activate the glucose molecule. Two ATP molecules are used in the early steps of the pathway. These ATP molecules help phosphorylate glucose and its intermediates, preparing them for further breakdown.

Step 2: ATP generation phase
In the later steps of glycolysis, energy is released as the intermediates are converted into pyruvate. During this stage, four ATP molecules are produced through substrate-level phosphorylation.

Step 3: Calculating the net ATP gain
Although four ATP molecules are produced, two ATP molecules were already consumed in the earlier stage. \[ \text{Net ATP gain} = \text{ATP produced} - \text{ATP consumed} \] \[ = 4 - 2 = 2 \text{ ATP} \] Conclusion:
Therefore, the net gain of ATP molecules during glycolysis is 2 ATP per molecule of glucose.