Life Power

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Life Power

Living things can use ATP like a battery. The ATP can power needed reactions by losing one of its phosphorous groups to form ADP, but you can use food energy in the mitochondria to convert the ADP back to ATP so that the energy is again available to do needed work. In plants, sunlight energy can be used to convert the less active compound back to the highly energetic form. For animals, you use the energy from your high energy storage molecules to do what you need to do to keep yourself alive, and then you "recharge" them to put them back in the high energy state. The oxidation of glucose operates in a cycle called the TCA cycle or Krebs cycle in eukaryotic cells to provide energy for the conversion of ADP to ATP.

The Calvin Cycle

Plants use energy from the sun in tiny energy factories called chloroplasts. Using chlorophyll in the process of photosynthesis, they convert the sun's energy into storable form in ordered sugar molecules such as glucose. In this way, carbon dioxide from the air and water from the soil in a more disordered state are combined to form the more ordered sugar molecules.

Carbon dioxide is captured in a cycle of reactions known as the Calvin cycle or the Calvin-Benson cycle after its discoverers. It is also known as just the C3 cycle. Those plants that utilize just the Calvin cycle for carbon fixation are known as C3 plants. Carbon dioxide diffuses into the stroma of chloroplasts and combines with a five-carbon sugar, ribulose1,5-biphosphate (RuBP). The enzyme that catalyzes this reaction is referred to as RuBisCo, a large molecule that may be the most abundant organic molecule on the Earth. This catalyzed reaction produces a 6-carbon intermediate which decays almost immediately to form two molecules of the 3-carbon compound 3-phosphoglyceric acid (3PGA). The fact that this 3-carbon molecule is the first stable product of photosynthesis leads to the practice of calling this cycle the C3 cycle.

Energy Cycle in Living Things A fascinating parallel between plant and animal life is in the use of tiny energy factories within the cells to handle the energy transformation processes necessary for life. In plants, these energy factories are called chloroplasts. They collect energy from the sun and use carbon dioxide and water in the process called photosynthesis to produce sugars. Animals can make use of the sugars provided by the plants in their own cellular energy factories, the mitochondria. These produce a versatile energy currency in the form of adenosine triphosphate (ATP). This high-energy molecule stores the energy we need to do just about everything we do. The energy cycle for life is fueled by the Sun. The main end product for plants and animals is the production of highly energetic molecules like ATP . These molecules store enough immediately available energy to allow plants and animals to do their necessary work.		Index Second law concepts
The functional work (energy transformations) of plants and animals.
Order and disorder in biological systems.
HyperPhysics***** Biology	R Nave	Go Back

The Work of Living Things There are a number of energy transformations in plants and animals which are essential to life. These processes will be described as the "work" of living things, although it is not immediately evident that they involve work in the physical sense. Some of the general kinds of processes involved in the energy cycle are:
Synthetic Work	Both plants and animals must make the complex molecules necessary for life. One example is the production of DNA - your genetic material. If you don't make extra copies of DNA, you will have no information to pass on to your offspring. Every time one of your cells makes a copy of itself, it has to make a new copy of the DNA. That synthesis process requires a lot of ATP. The process of growth requires a lot of synthetic work to create the new cells and enlarge the structures.
Electrical Work	You may not think of yourself as an electrically operated machine, but you are. Each of our cells has an electric potential associated with it. This potential, or voltage, helps to control the migration of ions across the cell membranes. A major example of electrical work is in the operation of the nerves. When your nerves fire, they generate an electrical impulse called an action potential which can communicate information to your brain, or carry a signal from your brain to a muscle to initiate its movement. Electrical energy transformation is essential for sensing your environment as well as for reacting to that environment in any way.
Mechanical Work	Most easily visualized is the mechanical work associated with the moving of our muscles. This muscle movement is very important and requires a lot of energy. The source of that energy is ATP