How does yeast work?

Yeast is a unicellular fungus that plays a vital role in the production of various fermented food products, including bread, beer, and wine. The process of fermentation involves the conversion of sugars into alcohol and carbon dioxide by yeast, which is facilitated by enzymes present within the yeast cells. Here's a simplified explanation of how yeast works:

1. Glucose Transport: Yeast cells actively transport glucose, a simple sugar, into their cells from the surrounding environment. Glucose serves as the primary energy source for yeast.

2. Glycolysis: Inside the yeast cells, glucose undergoes glycolysis, a series of enzymatic reactions that break down glucose into two molecules of pyruvate. This process occurs in the cytoplasm.

3. Pyruvate Decarboxylation: Pyruvate, the product of glycolysis, enters the mitochondria where it undergoes decarboxylation. This reaction catalyzed by the enzyme pyruvate decarboxylase, results in the release of carbon dioxide (CO2) and the formation of acetaldehyde.

4. Acetaldehyde Reduction: Acetaldehyde, the intermediate compound, is then reduced to ethanol (ethyl alcohol) by the enzyme alcohol dehydrogenase. This reaction consumes NADH (nicotinamide adenine dinucleotide), a high-energy electron carrier, and produces NAD+ (nicotinamide adenine dinucleotide).

5. Regeneration of NAD+: For the continuous process of fermentation, yeast cells need to regenerate NAD+ from NADH. This regeneration occurs through various mechanisms, including the electron transport chain, where NADH donates electrons, leading to the production of ATP (adenosine triphosphate), the energy currency of cells.

6. Budding and Cell Reproduction: As yeast cells undergo fermentation, they also reproduce through a process called budding. A small protrusion, known as a bud, emerges from the parent yeast cell. The bud grows and eventually detaches, forming a new yeast cell.

7. CO2 Production: The release of carbon dioxide (CO2) during fermentation gives rise to the characteristic bubbles and foam observed in fermenting mixtures. In bread making, CO2 causes the dough to rise, resulting in a fluffy texture. In beer and wine production, CO2 contributes to the effervescence and carbonation of these beverages.

Overall, yeast works through the process of fermentation, where it converts sugars into ethanol and carbon dioxide. The enzymes within yeast cells facilitate these reactions, enabling the production of various fermented food products such as bread, beer, wine, and many more.