A decrease in ATP concentration affects the activity of the enzyme pyruvate kinase in the glycolysis pathway by increasing its activity. Pyruvate kinase is an important enzyme in the glycolysis pathway, catalyzing the conversion of phosphoenolpyruvate PEP to pyruvate, with the generation of one molecule of ATP.ATP is an allosteric inhibitor of pyruvate kinase, meaning that it binds to a site on the enzyme other than the active site and modulates the enzyme's activity. When ATP levels are high, it indicates that the cell has sufficient energy, and there is no need for further ATP production through glycolysis. In this case, ATP binds to the allosteric site of pyruvate kinase, causing a conformational change in the enzyme's structure and reducing its activity. This inhibition helps to slow down the glycolysis pathway and conserve resources.On the other hand, when ATP concentration decreases, it implies that the cell requires more energy. The reduced ATP levels lead to less ATP binding to the allosteric site of pyruvate kinase, which in turn increases the enzyme's activity. This increased activity accelerates the glycolysis pathway, resulting in the production of more pyruvate and ATP to meet the cell's energy demands.In summary, a decrease in ATP concentration leads to increased activity of pyruvate kinase in the glycolysis pathway, promoting ATP production to fulfill the cell's energy requirements.