Using the Sun's Energy
chemical energy, sunlight energy, photosynthesis, chloroplasts
It's been a long day at school and you are tired. You have worked hard and there are still things you want to do today. Maybe you plan to ride your bike, walk your dog, or play ball. What do you do to feel better? Have something to eat! Make yourself a cheese sandwich and a glass of milk. After that snack, you will have more energy to do what you want.
Almost all living things need food to keep them going. Where does your food come from? Yes, you prepared the snack by putting the bread and other parts together and pouring milk into a glass, but you did not really make the food. The bread for the sandwich came from wheat, a plant, and the cheese and milk came from a cow. People and animals need to get their food from somewhere else, because they cannot make their own food.
Plants are different, though. They cannot make wheat into flour or milk a cow. They have to make their own food. They do it inside themselves. They don't need to hunt, work in a garden, or cook at a stove. Plants are like little factories. Photosynthesis is a process plants use to make food from the sun's light.
Sunshine makes food?
When a plant makes food, it needs to gather things from the world around it, just like you did when you made your sandwich. You got a plate from the cupboard and bread from the bread box. A plant uses water, which comes in through the roots. It needs a certain kind of gas. The gas enters through small holes in the leaves. The plant also uses power from the sun. Sunlight energy is energy from the sun in the form of light that plants use to make their own food.
Sunlight is gathered during the day much like the way a sponge sucks up water. It happens inside very small parts of the cells of the leaves. These small parts are not found in animal cells but are in plant cells. One plant cell might have fifty of these tiny parts. There is stuff inside these parts that give plants their green color. The parts that grab sunlight to help make food for the plant are called chloroplasts.
The sunlight has to be changed before the plant can use it, just like the bread in your sandwich needs to be changed before you can use it. Your body breaks the bread into very, very small pieces called sugars. Your body uses these sugars for the energy you need to live. It's the same for plants: inside those tiny cell parts, the sunlight is changed into chemical energy. Chemical energy is the energy stored in molecules, like sugars, that living things can use to make the energy they need to live. People are different than plants, though. Believe it or not, you would get tired of eating just sugar, because people and animals need many different kinds of food to live and grow.
Sunlight is like sugar to plants.
Plants make their own food, but that's not the end of the story. This task helps people and animals, too. When plants make food, they end up with oxygen, but they can't use it. It goes into the air for people and animals to breathe. You do something like this when you breathe: you use oxygen, the gas you need, and breathe out the gas you don't need. Then plants use this waste gas to help make their food.
But wait - there's more! All people and animals use plants in some way. Lots of animals graze on plants. Some animals, like lions, just eat meat, but the animals they hunt fed on plants. Most people eat both plants (fruits, vegetables, grains) and animals (cow, pigs, chickens), so we really need plants. By making their own food, plants take care of themselves and help take care of us, too.