Competency 208: Carbohydrate Metabolism

Competency 208.5.4: Enzymology and Catalytic Mechanism Competency 208.5.5: Carbohydrate Metabolism, Adenosine Hadassah Backman, RN Western Governor’s University

Enzymes, are macromolecules which serve as catalysts. Catalysts are a chemical that can increase the rate of a chemical reaction or slow it down, without being changed by the reaction itself. The enzyme as a catalyst promotes the activity of the reactant which subsequently produces the product.
Enzymes have the ability to work under milder conditions, as they do not require the same level of energy, force or heat that other chemical catalysts may require to produce a biochemical reaction.
Enzymes bind temporarily to their substrates, to carry out the

This occurs when the muscle is undergoing rigorous exercise without sufficient oxygen supply. Anaerobic respiration takes place to support the muscles energy need. After this occurs, lactate is brought back to liver to be converted back to glucose. In the muscles, when glucose is converted to lactate it produces 2 ATP, rather than allow lactate to build up in the muscles, the second half of the Cori Cycle occurs, gluconeogenesis takes place, and reverses the both glycolysis and the fermentation, by using 6 ATP to convert lactate, to pyruvate, which can then proceed to the Krebs (citric acid cycle). If there is a mitochondrial defect present that prevents the lactate from being converted to pyruvate, limiting the Cori Cycle to the muscle cell, then the lactic acid will accumulate within the muscle cell and will result in a decreased amount of ATP production. The Cori cycle is self-limiting and will consume ATP without the ability to “re-stock” through the Krebs cycle, which produces more ATP molecules than the Cori

Ultimately only 10 ATP would be produced should a mitochondrial defect be present, which limits the Cori Cycle to a muscle cell.
A hypothetical defect of the enzyme succinic coenzyme A synthetase, would have catastrophic effects, as it is one of the central catalysts involved in the Citric Acid Cycle. It is the only enzyme in the citric acid cycle that produces GTP or ATP through substrate level phosphorylation. The rest of the enzymes produce products that go on to the electron carrier chain, and ultimately produce ATP, but in the Citric Acid Cycle Succinyl Coenzyme synthetase is the only enzyme responsible for producing GTP. Without this enzyme, cells would resort to producing lactic acid in order to obtain ATP, this would ultimately result in acidosis and death. The Citric Acid cycle would cease to function because there would be no ATP present in the mitochondria to support oxidative phosphorylation, which yields the most ATP by converting the NADH and FADH produced in the citric acid cycle to