During a marathon, runners draw heavily on their internal reserves of glycogen (carbohydrate) and triglycerides (fat) to fuel mu
scle contraction. Initially, energy is derived mostly from carbohydrates, with increasing amounts of fat being used as the race progresses. If runners use up their muscle glycogen reserves before they finish the race, they hit what is known as "the wall.," a point of diminished performance that arises because fatty acids from triglyceride breakdown cannot be delivered to the muscles quickly enough to sustain maximum effort. One trick that marathon runners use to avoid the wall is to drink a cup of strong black coffee an hour or so before the race begins. Coffee contains caffeine, which is an inhibitor of cyclic AMP phosphodiesterase. How do you suppose inhibition of this enzyme helps them avoid the wall
The activity of cyclic AMP phosphodiesterase is prevented by caffeine. The caffeine prevents further dissociation of cAMP, which eventually increases the response within the body. The activity of neurotransmitters, that is, of noradrenaline or epinephrine, gets increased due to enhancement in response.
This further enhances the activity of the heart, the rate of muscle contractions, blood pressure that further helps in delivering more oxygen to the brain, and other parts of the body. Thus, the inhibition of the enzyme cyclic AMP phosphodiesterase helps the athletes to prevent the wall.
Mitochondria are structures within cells that convert the energy from food into a form that cells can use. Mitochondrial DNA contains 37 genes, all of which are essential for normal mitochondrial function. Thirteen of these genes provide instructions for making enzymes involved in oxidative phosphorylation.
It follows that the carnivores (secondary consumers) that feed on herbivores and detritivores and those that eat other carnivores (tertiary consumers) have the lowest amount of energy available to them.
