What are the primary end products of glucose metabolism in yeast?

The main products of glucose breakdown in yeast are ethanol (alcohol) and carbon dioxide (CO₂). This happens through a process called alcoholic fermentation, which occurs without oxygen. Yeast uses this process to extract energy from glucose.

Steps in the process:

1. Glycolysis: Glucose is split into two molecules of pyruvate.
2. Pyruvate conversion: Each pyruvate is changed into acetaldehyde, releasing carbon dioxide.
3. Ethanol formation: Acetaldehyde is then converted into ethanol. During this step, NAD⁺ is regenerated, which is essential for glycolysis to keep running.

Overall equation of alcoholic fermentation: 

C₆H₁₂0_6-2C₂H₅OH + 2CO₂

Products in the Presence of Oxygen

When oxygen is available, yeast switches to aerobic respiration instead of fermentation. This leads to very different results.

Steps in the process:

1. Pyruvate enters the citric acid cycle and then goes through oxidative phosphorylation.
2. End products: Glucose is completely broken down into carbon dioxide and water, and this process produces a much larger amount of ATP (energy) compared to fermentation.