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. Both animal and plant cells contain mitochondria and plants have the additional energy factories called chloroplasts. The chloroplasts 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 energy factories 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.

The functional work (energy transformations) of plants and animals.
Order and disorder in biological systems.
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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.

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