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Friday, February 11, 2011

How plants manufacture food for us.

Plants need energy to grow, to replace worn out cells, to get rid of waste, and to reproduce. All organisms get energy from food. Photosynthesis is the process by which plants make food. Only plants can make food.
In this process carbon dioxide and water combine in the presence of light to form sugar, a food. Stomates are found in layers of protective cells on the surface of the leaf. Gases move in and out of stomates. These openings connect to large air spaces in the middle layer of the leaf. Carbon dioxide in the middle layer of the leaf is available to the food-making cells of the leaf. Xylem in the vein carries water to the food-making cells. The water comes from the roots and the root hairs which are in the ground.
You can think of a chloroplast as a food factory. Carbon dioxide and water are the raw materials that go into the factory. Sunlight is the energy that changes the raw materials into the product, food in the form of sugar.
Photosynthesis is a complex process. A series of chemical reactions change the raw materials to the food product. The process can be shown simply by looking at the starting materials and the end products.
WATER + CARBON DIOXIDE + ENERGY ---> SUGAR + OXYGEN
Respiration is the process by which plants discard the materials that they don't use. For example, in photosynthesis, when plants take in cardon dioxide, they let out oxygen, which is what we breathe. This is how we always have fresh air.

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