In computational complexity theory, a problem refers to the abstract question to be solved. In contrast, an instance of this problem is a rather concrete utterance, which can serve as the input for a decision problem. For example, consider the problem of primality testing.
Oxygen plays a vital role in both the aerobic and anaerobic metabolic systems. While oxygen is required as a direct energy source in the aerobic system, it is also essential in clearing the blood of excess lactic acid buildup in the anaerobic system.
Anaerobic glucose metabolism (anaerobic glycolysis) occurs in oxygen deprived cells and cells which cannot preform aerobic glycolysis (e.g. red blood cells). A byproduct of anaerobic glycolysis is lactic acid, which we will discuss more in a later post.