Under ideal conditions, the fermentation of one glucose molecule by a bacterium allows a net gain of how many ATP molecules?
a. 2
b. 4
c. 38
d. 0

Verified step by step guidance

1. Identify the process involved: Fermentation is an anaerobic process where glucose is converted into energy.
2. Understand the main pathways: In fermentation, glucose is primarily broken down through glycolysis.
3. Calculate ATP yield from glycolysis: Glycolysis converts one glucose molecule into two pyruvate molecules, yielding a net gain of 2 ATP molecules.
4. Consider the fate of pyruvate: In fermentation, pyruvate is converted into various end products (like lactic acid or ethanol) without further ATP gain.
5. Conclude the net ATP gain: Since no additional ATP is produced beyond glycolysis in fermentation, the net gain remains the same.

Key Concepts

Fermentation

Fermentation is an anaerobic metabolic process where microorganisms convert sugars, such as glucose, into acids, gases, or alcohol. In the absence of oxygen, bacteria utilize fermentation pathways to generate energy, primarily in the form of ATP. This process is less efficient than aerobic respiration, yielding fewer ATP molecules per glucose molecule.

ATP Yield in Fermentation

During fermentation, the net gain of ATP from one glucose molecule is typically 2 ATP molecules. This is because fermentation involves substrate-level phosphorylation, where ATP is produced directly from the energy released during the conversion of glucose to fermentation products, such as lactic acid or ethanol.

Comparison with Aerobic Respiration

Aerobic respiration, in contrast to fermentation, can yield up to 38 ATP molecules from one glucose molecule due to the complete oxidation of glucose in the presence of oxygen. This process involves glycolysis, the Krebs cycle, and the electron transport chain, making it significantly more efficient than fermentation, which is limited to anaerobic conditions.