Why+do+we+breath

=Your body is made up of tiny **cells**, each of which has a special job that keeps you alive. Every cell in your body needs a special gas called **oxygen**, that allows the cell to get energy from the food you eat. Oxygen in the air is brought into your lungs. That's when your blood picks it up and brings it to your cells. = =Another gas, calledcarbon dioxide **is a waste product of yourcells. It is very dangerous if it builds up in your body. Your blood carries the carbon dioxide from your cells to your lungs, to let you breathe out all the bad gas!** = =When we exercise, our cells are working harder, and they need **more** oxygen. They also produce **more** carbon dioxide. That's why you breathe faster when you exercise! = =You have probably noticed that when you're exercising, your heart beats more quickly. That's so that the blood can carry oxygen to your cells faster! = =Your heart and lungs work **together** to make sure every cell in your body gets enoug**h oxygen**  = =What do you think happens to the speed of our breathing when we're resting? = =When you rest, your cells aren't working very hard, so they need**less** oxygen. They also produce **less**carbon dioxide. This means that you don't need to breathe as often as when you're moving around. Remember that because the heart and lungs work as a team, when your lungs are not working hard, your heart is not working hard either. =