Anaerobic
Respiration
Simplified

1. Lactic Acid Fermentation

This occurs with the absence of oxygen and is typically used in many food or beverages processes. This can be seen in everyday foods such as milk, bread, and even cereal. 

Glucose is inputed along with 2 ADP, without is converted to 2 ATP as a net product. NAD+ is used as an intermediate electron carrier during glycolysis. Reminder, the absence of oxygen prevents the cell from undergoing aerobic respiration, therefore the cycle ends after glycolysis. 

This cycle yields a total of 2 Lactate Acid, and 2 ATP. Comparatively a significant amount less of ATP produced than Aerobic Respiration.

2. Ethanol (Alcohol) Fermentation

This occurs similar to Lactic Acid yet instead of producing two Lactate, it produces ethanol or alcohol instead. This is where sugars such as glucose are broken down by microorganism more typically seen as yeast to produce alcohol and carbon dioxide. 

1. Sugar (glucose) is first taken in by yeast.

2. Glucose is then broken down to pyruvate through glycolysis. We should be familiar with this term which breaks down a simple sugar glucose into two molecules of pyruvate, and 2 molecules of ATP (small amounts).

3. Ethanol and Co2 is then converted in the last step. Pyruvate is then converted into Acetyl Coenzyme A which is an intermediate and not too important (don't stress over this) into Alcohol and Co2. Since the yeast needs to regenerate NAD+, this is essential for the continuation of glycolysis. 

Chemical Reaction:
C6H12O6 --> 2C2H5OH + 2CO2