Question

I have a question regarding ATP during exercise. It's kind of long so bear with me. So I understand that when you are exercising, your body first uses the small supply of ATP that it has, which can be stored in creatine phosphate, which I know only lasts 8-10 seconds. My question is what source of ATP comes next? I always thought oxidative phosphorlyation came next, and then after that gets depleted THEN your body undergoes anerobic glycolysis. My thought of that was challenged in a discussion board for Human Physiology today, and now I am not exactly sure. This person said that your body uses the ATP it has stored first, like in creatine phosphate. She then said this is when anerobic glycolysis kicks in, which uses pyruvate and converts it to lactate, and it can do this without oxgen. After a short time span, lactate is built up and the process can no longer go forward because the environment has become too acidic. NOW is when she said oxidative phosphorylation kicks in. She said that it takes longer for glucose to be converted to acetyl CoA then go through the Krebs cycle and then be converted to electron carriers like NADH and FADH2, but once all this has taken place, NOW we produce a lot of ATP (30-32 per glucose). This sounds correct to me, but I wanted to get another opinion of it, and I really can't find anywhere online that explains it well. Thank you in advance!!!

Answer 1

ATP is required for muscle contraction during exercise. Initially, creatine phosphate high potential phosphoryl group to ADP to generate ATP, however its supply is limited and lasts only for 8-10 seconds. After this the muscle glycogen is degraded into glucose which undergo glycolysis to produce pyruvate, but under low oxygen conditions(during exercise) pyruvate is reduced to lactate to allow continuous ATP production. But this leads to accumulation of lactate in muscle cells. This process cannot be sustained for a longer time and within 2 minutes the body starts to supply oxygen to exercising muscles, and the muscle switches to aerobic respiration. Pyruvate obtained from glycolysis is oxidized to ATP via krebs cycle, although this step is slower than anaerobic respiration but it can supply ATP for several hours or longer as longer as the fuel is available.