Fermentation

For glycolysis to keep running, NAD+ is needed (remember… to take the hydrogen in step 6) 

Under aerobic circumstances where the pyruvate would eventually enter the TCA cycle and the ETC, these hydrogens would be removed for energy and replenished. 

However, under anaerobic conditions, this does not occur. This results in a need for...

→ Lactic acid fermentation! (In animals) 

• Organisms can regenerate NAD+ by reducing pyruvate into lactate and NAD+ 

• This is done by the enzyme lactate dehydrogenase

• It occurs in red blood cells, and with intense exercise. 

In yeast, Ethanol fermentation occurs

This has two steps: 

1. Pyruvate → Acetaldehyde + CO2 

   1. By pyruvate decarboxylase 

2. Acetaldehyde + NADH → NAD+ + Ethanol 

   1. Alcohol dehydrogenase