Metabolic Acidosis

More than any other Section of this text, you must mentally release all the "facts" you have been told and start this reading with a fresh mind.  You now have all the biochemistry knowledge to understand all that I will be teaching you about the biochemistry of proton (H+) balance in cellular and systemic fluid compartments. Indeed, the source of the H+ load of intense muscle contraction that causes a cellular and systemic acidosis is not complicated. It is also logical that considerably more H+ release accompanies intense exercise than lactate is produced. As lactate consumes 1 H+ as it is produced, this has to be the case. Then there are all the H+ dynamics that accompany hyperventilation and blood acid-base balance through the bicarbonate-ventilation system of blood H+ buffering. When strictly dealing with events within contracting skeletal muscle, you already know that the H+ release from glycolysis in addition to ATP hydrolysis account for most of the H+ load of intense muscle contraction. Of course, the exact amount is difficult to compute given the H+ dependence of certain chemical reactions, and the involvement of mitochondrial uptake of H+ via numerous mitochondrial H+ co-transport proteins. However, these complexities do not detract from the clear involvement of H+ in chemical reactions. For too long, we have blamed lactate because of history and the ease of a one molecule, blame all mentality. While I often state to be aware of the overly complex answer in physiology, the opposite extreme is also true; nothing is really a simple or as clear, or as "proven" as many like to believe. I think this reflects the vanity of humanity. We like to think we know things or have solved problems; to have the answer. We do not like to admit that what we still might be wrong.

Recommended sequence of topics:

What is pH?

Acids and bases

Why there is no such molecule as lactic acid in the body

Biochemistry of exercise-induced metabolic acidosis

The physico-chemical theory of acid-base balance