Why did yeast grow in presence of oxygen?
Yeast grew in the container with oxygen meaning it is anaerobic. The next question is whether it is an obligate or a facultative anaerobe. I assume that yeast still grew in the container w/o O2. If it did, then it justifies the fact that yeast is a facultative anaerobe. Facultative anaerobes can undergo metabolism with or without the presence of oxygen, O2. The glycolytic pathway of catabolism is the common way of breaking down sugars (i.e. glucose) and it uses oxygen. At the end of Glycolysis, the Krebs Cycle, and the Electron Transport Chain (ETC), one glucose molecule yields a net of 38 ATP’s. On the other hand, fermentation is a process which yeast undergoes and is an anaerobic process. Fermentation releases energy from sugars or other organic molecules but does not require oxygen but it in turn produces less ATP’s. Let’s take glucose for example. In glycolysis, 2 NAD+ is reduced to 2 NADH, while 2 ADP is converted to 2 ATP. The end-product of glycolysis is 2 pyruvate (pyruvic acid
