Energy for life...! (EN)
Every plant, animal, and living cell is a living machine and, just like a mechanical machine, needs an energy supply. The fuels for most animal life on this planet are various hydrocarbon compounds that react with oxygen to reléase energy. As with the petroleum fuel, the "combustion of food in a cell (part of what is called metabolism) creates carbon dioxide and wáter and releases energy to sustain life.
The principal difference between the combustion of food in digestion and the combustion of fossil fuels in mechanical engines is the rate at which reactions take place. In digestion the reaction is much slower and energy is released as it is required.
Like the burning of fossil fuels, the reaction is self-sustaining once started, asvcarbon combines with oxygen to form carbon dioxide and hydrogen with oxygen to form water.
The reverse process is more difficult. Only green plants can make carbon dioxide combine with water to produce hydrocarbon compounds such as sugar.This process is photosynthesis and is energized by sunlight. Sugar is the simplest food, and all others carbohydrates, proteins, and fats are also synthe sized compounds of carbon, hydrogen, oxygen, and other elements.
How very fortunate that more energy is locked in the bonds of these hydrocarbons than in their products after combustion!
We see efficiency at work in the food chain. Larger creatures feed on smaller creatures, who in turn eat smaller creatures, and so on down the line to land plants and Ocean plankton that are nourished by the sun. Moving each step up the food chain in volves inefficiency. In the African bush, 10 kilograms of grass may produce 1 kilogram of gazelle. How ever, it will take 10 kilograms of gazelle to sustain 1 kilogram of lion.
We see that each energy transformation along the food chain contributes to overall inefficiency. Interestingly enough, some of the largest creatures on the planet, the elephant and the blue whale, eat far down on the food chain. And more and more humans are considering substances such as krill or yeast as efficient sources of nourishment.
