14. Photosynthesis—the source of food for life

by Xuefeng

To survive, man needs not only air, water, and salt, but also needs to absorb nutrition, mainly carbohydrate.

Where does carbohydrate come from?

It comes from photosynthesis.

What is photosynthesis?

Photosynthesis is a process of converting sunlight energy to chemical energy through carbon dioxide and water to produce the nutrition needed by animals and plants—carbohydrates.

Human body itself cannot conduct photosynthesis, neither can any other animals. Photosynthesis mainly occurs within green plants. Therefore man must live on green plants.

Photosynthesis can be briefly described as follows:

When sunlight shines upon the leaves of plants, it will be captured by chlorophyll in the cells of leaves. The light energy captured by chlorophyll will decompose the water entering the leaves via roots into hydrogen and oxygen. Oxygen will be released through the pores on the leaves, while hydrogen will be kept within leaves and will react with carbon dioxide entering the leaves via pores on the leaves to form carbohydrates. The vigorous carbohydrates will spread in the plant cells through veins and enable the absorption and growth of plants.

The most common type of carbohydrate is glucose, which will combine with nitrogen to form amino acids, proteins, and nucleic acids needed by life. Nitrogen is carried inside plants mainly through the water absorbed by the root systems of plants.

Because of photosynthesis, part of carbohydrates formed inside the plants will be supplied to plant itself, and the rest will be stored in the leaves and fruits. Man and animals absorb carbohydrates by consuming the leaves and fruits of plants.

Carbohydrates are compounds composed of carbon, hydrogen, and oxygen atoms. Sugar, glucose, and fructose are simple carbohydrates, while starch and cellulose are more complex carbohydrates. The molecules of simple carbohydrates have only a few carbon and hydrogen atoms, while the molecules of complex carbohydrates have many carbon and hydrogen atoms.

In terms of sources, all the food we eat originates from photosynthesis. Without photosynthesis, there would be no humans. Some people argue, “I do not rely on plants, and can survive only on poultry and domesticated animals, so I don't need the photosynthesis of plants.” The problem is without the photosynthesis of plants, there would be no poultry and domesticated animals, because they rely on plants for survival. Of course we can survive by eating fish, but fish also live on the photosynthesis of algae and some indigenous microorganism.

From the point of nature, the only living things capable of making food are plants. Animals and men are not capable of making food themselves, because animal body and human body do not have the element for photosynthesis.

In addition to providing food for itself, animals, and man, the photosynthesis of plant has a tremendous function—the absorption of carbon dioxide and the release of oxygen.

If plants do not make oxygen, animals and plants would have died out long before. If the plants do not absorb the carbon dioxide, the carbon dioxide in the atmosphere will exceed the constant, and greenhouse effect will aggravate, and the temperature of the earth would be too high for man and animals to survive.

Do you think that the photosynthesis of plants begins and happens incidentally?