Many homes are made up of more than one room. These rooms can vary a lot in size. Some homes have huge living rooms and tiny bedrooms. Each is used for something different, such as sleeping, bathing, eating, and cooking. Sometimes they have more than one use, like a bedroom that is also a home office. Somewhere in your home you have a place to do everything you need to, such as making food. You do this in the kitchen, even though you might eat somewhere else.
Green plants are like houses because they are made up of many parts. They even have their own "kitchen" inside their cells where they make food. However, they do not just take their food from the outside world like animals do. They bring things inside themselves and use those things to make their own food. The chloroplast is the part of a plant cell where food for the plant is made. These parts are never found in animals. They are only found in plants.
Each plant needs millions of these parts, because plants need a great deal of food to grow and live. You have to take several steps in order to eat a sandwich: get the bread, add the topping, put it together, and chew it up. It also takes many steps for a plant to make its food. First, the plant needs to get energy from the sun. How do they do it? A plant cannot just gather food in a basket, like when you pick cherries or apples. It has to collect the sunlight somehow.
A plant gathers sunlight like a sponge soaks up water. The water holds on to the sponge and fills in the holes. Other things can gather sunlight, too. Our skin soaks up some of it to help keep us warm. We can't use it to make food, though. Think of a street on a sunny summer day. How does the pavement feel if you touch it? It's really hot! The street has soaked up the sunlight, making the pavement warmer. Our skin and the pavement absorb the sunlight. To absorb
means to take something in and hold it.
The chloroplasts of plant cells have stuff that takes in sunlight. This chemical, found only in plants, starts the task of making food. Animal cells have no need for it because most animals are able to move around to find the food they need. Chlorophyll
is the chemical inside plant cells that gathers energy from sunlight. Plants use this energy to make their own food. It is found only in the green plant parts, like leaves, stems, and unripe fruit.
Why only green parts? This has to do with light, which is made up of all the colors of the rainbow. Light is the reason plants are green and people come in so many different colors. Look at your arm: is it almost white, tan, or very dark? There's a kind of coloring that decides how light or how dark your skin will be. The more you have of this coloring, the darker your skin. Pigments
are the substances that make things certain colors.
Rainbows need water too.
Think of skin color like this: there is a white circle in front of you, and you have a dark brown pen in your hand. If you make only a few dots with your brown pen, your white circle will still look pretty white. If you make more dots, the circle will look a little darker. The more dots you make, the darker the circle will become. Just like the white circle, people's skin color depends on how much pigment they have in their skin cells. Chlorophyll is a pigment found in plants.
The plant has gathered sunlight, but is not ready to make food yet. If you are making a sandwich, you need more than just bread. You might want ham and cheese, too. The plant also needs other things to make its own food. It needs water and a gas called carbon dioxide. It gets this gas from the air after animals have breathed it out. Then the plant is ready to go.
Plants need water just like people need water.
The plant uses energy from the sunlight to bring together the water and gas. This makes food so the plant can live and grow. Animals need food for energy too, but they must get it from the outside world. Then animals' bodies break down the food and use it right away or store it for later. Animals break down a lot of their food into something made of many sugars, a carbohydrate. A carbohydrate
is made of many sugars stuck together, and plants and animals can use them for energy or can store them for later. It's also the food that plants make.
Plants need to break down this sugar, too. When a plant needs energy, it breaks the sugar into tiny pieces that are easy to use. This does not happen in the same part of the cell as where the food is made. It's like when you make your food in one room and eat it in a different room. A plant needs different parts of its cell to first make, then use food.
The plants end up using the sugar they make, but they are also left with oxygen. Plants cannot use oxygen, so they let this gas go into the air. Although plants do not need it, animals need oxygen to stay alive. This works out very well. The thing we need to breathe in order to stay alive is the thing that the plants do not need! Plants are one of the ways that animals get the oxygen they need.
All living things need energy for their day-to-day tasks. Animals have to find food so they can hunt, hide, and sleep. In your kitchen, you have food so you can walk around, play, go to school, and ride your bicycle. Plants make food they need so they can grow bigger, make fruit, and grow longer roots to hold themselves up. Plants may not have real kitchens, but they have places inside their cells where they take things that are not food, such as water, sunlight, and a gas, and turn them into sugar. This makes plants very special among living things.