17 Food and Nutrition-Low

Food and Nutrition Written by Katherine Follett

What Needs Food? All living things need energy. They need it to live, to do all the things they do each day, and to stay healthy. Living things get this energy from food. In this book, you will learn how plants and animals get food. You will also find out how living things use food for energy. Before reading on, think about how plants get food. Do they eat? Then think about how plants use food for energy.

How Do Plants Get Food? Plants and animals get the energy they need in different ways. Animals eat food. But plants don't eat. Plants make their own food through a process called photosynthesis. Plants don't get food from soil. During photosynthesis, plants make a simple kind of sugar. The sugar is their food. Green plants soak up light energy from the Sun and use it to make the sugar. Plants also use a gas in the air called carbon dioxide. Plants take in carbon dioxide through tiny holes on the bottoms of their leaves. Plants make food using sunlight, carbon dioxide, and water. It is true that soil does not provide plants with food. But soil does give plants water and minerals. Both of these things are soaked up through the roots. Water and minerals are important during photosynthesis. Study the diagram of a plant on page 6. It explains the steps of photosynthesis that take place inside green plants.

Photosynthesis in Green Plants 1 Roots take in water. The plant carries the water to the plant's cells. 2 The cells have a green material in them called chlorophyll. Chlorophyll captures the Sun's energy. 3 Leaves take in carbon dioxide from the air through tiny holes. 4 The leaf cells use the Sun's energy to break down the carbon dioxide and water. They turn the chemicals into a simple sugar. The sugar is the plant's food. 5 The plant uses some of the sugar. It stores the rest in its leaves, stem, roots, and other parts. 6 When plants make sugar, some oxygen gas is left over. The leaves give off the oxygen into the air through the tiny holes.

In the formula below, the left side explains what plants use during photosynthesis. The right side explains what plants produce during photosynthesis. The arrow is like an equal sign. How Do Plants Use Food for Energy? After photosynthesis happens, the plant has sugar for food. The sugar contains energy. The plant stores some of this energy in its leaves, stem, roots, fruit, and other parts. It uses the rest of the energy to grow by making new cells. So how does the plant get energy from sugar? The plant breaks down the sugar using respiration. Respiration is the opposite of photosynthesis. During respiration, the plant takes in oxygen from the air. It mixes the oxygen with the sugar to get the energy it needs. Then the plant sends water vapor and carbon dioxide back into the air. The next formula explains what plants use (on the left) and what they produce (on the right) during respiration.

To review, plants make their own food during photosynthesis. Then they use the energy from that food during respiration. Photosynthesis happens in sunlight. But respiration can happen in either the dark or the light. All living things use respiration to get energy from food. But plants also use photosynthesis to make their own food. This chart compares photosynthesis and respiration. Photosynthesis Respiration produces food uses food stores energy releases energy uses water uses sugar glucose uses carbon dioxide uses oxygen produces sugar glucose produces water vapor produces oxygen produces carbon dioxide occurs in sunlight occurs in the dark or light used mainly by plants used by all living things Try This To prove that plants give off water, seal a bag over a few plant leaves for a few days. See what happens.