31
reacts with a fuel source (often carbon based) and heat. Carbon not only oxidizes
when organic matter ignites and burns with a plentiful supply of air but also during
animal cellular respiration. All these processes are irreversible.
2.8 Work and Value
The seventeenth century ushered in the Enlightenment and accelerated new technological developments throughout every subsequent century. As newly specialized
scientific disciplines, primarily biology, chemistry, and physics, produced empirically measurable definitions for work, economic systems began to value maximizing productive yields on energy investments. High-value goods and services
typically require high oxidation rates of carbon in one form or another. In an age
before machines burned fossil fuels, energy was primarily converted and embodied
through human or animal labor.
7
More work required more physical effort, and there
was a biological limit to what could be accomplished.
2.8.1 Animal Power
Work produced by the bodies of people and draft animals is, at root, a product of the
chemical energy conversion by adenosine triphosphate (ATP) to adenosine diphosphate (ADP) through hydrolysis (as ATP reacts with water) in the cellular metabolism process. This is the fundamental energetic mechanism of all life. It works like
a toggle switch. Each time a phosphate is loosened from one ATP molecule in a cell,
tiny amounts of energy are released.
8
The macronutrients (carbohydrates, fats, and
proteins) and micronutrients (vitamins and minerals) in food supply new highenergy electrons to toggle the switch back, and ADP is converted into ATP again.
This extremely small amount of energy is multiplied by a staggeringly large number
of molecules working constantly. Each of our cells contains approximately a billion
ATP molecules. This flow of electrons powers all biosynthesis processes, the maintenance of cellular homeostasis, and the contraction of muscles. Oxygen is the most
common element in the human body. Proper metabolism in animals is possible only
when oxygen is available as a catalyst as discussed below and even though oxidative
phosphorylation (ADP to ATP) acts as a reversible switch, electron leaks create
7 Notable exceptions were sailing ships propelled by wind and mills that employed the kinetic
energy of wind and water to operate when these renewable energy resources were flowing (Smil
2008, p. 201).
8 About 31,000 joules per mol of ATP molecules are released in humans at normal body temperatures (Atkins and Paula, 2010, p. 212). Some mammals may release up to 50 kj per mol of ATP
(Smil 2008, p. 39).
2.8 Work and Value
reacts with a fuel source (often carbon based) and heat. Carbon not only oxidizes
when organic matter ignites and burns with a plentiful supply of air but also during
animal cellular respiration. All these processes are irreversible.
2.8 Work and Value
The seventeenth century ushered in the Enlightenment and accelerated new technological developments throughout every subsequent century. As newly specialized
scientific disciplines, primarily biology, chemistry, and physics, produced empirically measurable definitions for work, economic systems began to value maximizing productive yields on energy investments. High-value goods and services
typically require high oxidation rates of carbon in one form or another. In an age
before machines burned fossil fuels, energy was primarily converted and embodied
through human or animal labor.
7
More work required more physical effort, and there
was a biological limit to what could be accomplished.
2.8.1 Animal Power
Work produced by the bodies of people and draft animals is, at root, a product of the
chemical energy conversion by adenosine triphosphate (ATP) to adenosine diphosphate (ADP) through hydrolysis (as ATP reacts with water) in the cellular metabolism process. This is the fundamental energetic mechanism of all life. It works like
a toggle switch. Each time a phosphate is loosened from one ATP molecule in a cell,
tiny amounts of energy are released.
8
The macronutrients (carbohydrates, fats, and
proteins) and micronutrients (vitamins and minerals) in food supply new highenergy electrons to toggle the switch back, and ADP is converted into ATP again.
This extremely small amount of energy is multiplied by a staggeringly large number
of molecules working constantly. Each of our cells contains approximately a billion
ATP molecules. This flow of electrons powers all biosynthesis processes, the maintenance of cellular homeostasis, and the contraction of muscles. Oxygen is the most
common element in the human body. Proper metabolism in animals is possible only
when oxygen is available as a catalyst as discussed below and even though oxidative
phosphorylation (ADP to ATP) acts as a reversible switch, electron leaks create
7 Notable exceptions were sailing ships propelled by wind and mills that employed the kinetic
energy of wind and water to operate when these renewable energy resources were flowing (Smil
2008, p. 201).
8 About 31,000 joules per mol of ATP molecules are released in humans at normal body temperatures (Atkins and Paula, 2010, p. 212). Some mammals may release up to 50 kj per mol of ATP
(Smil 2008, p. 39).
2.8 Work and Value