Final answer:
Glycolysis is an anaerobic process that does not require oxygen. It produces a minimal amount of ATP compared to the Krebs cycle and electron transport. Some organisms can produce ATP through fermentation without oxygen.
Step-by-step explanation:
Glycolysis is an anaerobic process - it does not need oxygen to proceed. This process produces a minimal amount of ATP. The Krebs cycle and electron transport do need oxygen to proceed, and in the presence of oxygen, these processes produce much more ATP than glycolysis alone.
Some organisms can produce ATP from glucose by anaerobic respiration, which does not require oxygen. Many human cells perform fermentation that also does not require oxygen. There are two types: alcoholic fermentation and lactic acid fermentation. Both start with glycolysis.
Cellular respiration always begins with glycolysis, which can occur either in the absence or presence of oxygen. Cellular respiration that proceeds in the absence of oxygen is anaerobic respiration. Cellular respiration that proceeds in the presence of oxygen is aerobic respiration.