You are made out of trillions of cells. That is a pretty big number! Imagine that you have as many cells inside of you as there are stars in our galaxy.
Cells are a lot like the city you live in. There are many parts in a cell. Each part has a special job.
This is a picture of a real cell. It is from the inside of your cheek. It is a skin cell. The part in the middle of the circle is the NUCLEUS (NEW-CLEE-US). It is in charge of the cell. The NUCLEUS has all the directions the cell needs to do its job. This is called DNA. The NUCLEUS is like CITY HALL. The mayor and city council make the decisions about what will go on in the city.
The CELL MEMBRANE goes all the way around the outside of the cell. It helps to keep the cell safe. It is like the police and fire departments in the city. It is also like a fence with a gate in it. The CELL MEMBRANE keeps out anything that doesn’t belong in the cell. It lets in water, sugar, oxygen and other things the cell needs to do its job. It lets out wastes like carbon dioxide. It also lets out proteins that the cell has made for the body to use to make things like muscles and skin.
This is a picture of a MITOCHONDRIA. It sounds like “MIGHT-OH-CON-DREE-AH”. Mighty is a good word to think of when you think about this cell part. This is like a Power Plant. It makes all the power for the cell. It uses sugars from the food you eat to make energy called ATP. Kind of like the gas your car needs to go or the electric you need to run your TV.
This is a RIBOSOME. Its job is to make proteins. Every part of you is made out of proteins. In fact, all living things are made out of proteins! The RIBOSOME is like a FACTORY making all the different things you use at home and in school.
This is ROUGH ENDOPLASMIC RETICULUM. That is a big word for a part that does a big job. Its job is to move proteins around the cell. Just like buses, cars and trucks move things around in a city. The RIBOSOMES are found on the surface of the ROUGH ENDOPLASMIC RETICULUM. SMOOTH ENDOPLASMIC RETICULUM moves energy from inside the cell to the rest of the body. It is like POWER LINES, ROADS and WATER LINES.
VACUOLES are used by the cell to store extra water, wastes and food. In a city, we use water towers, landfills, rental storage units, warehouses and sheds to store things.
GOLGI BODIES (GOAL-GEE) package up and ship out of the cell the proteins made by the RIBOSOMES. They are like the post office and UPS.
CYTOPLASM fills up the spaces in-between all the other parts of a cell. It is almost like jelly. In a city, the houses, parks and people would be like the CYTOPLASM.
RNA is a copy of all the directions the cell needs to do its job. RNA is found in the NUCLEOLUS (NEW-CLEE-OH-LUS). The cell parts use the RNA to find out what job they need to do. DNA is the original copy of these directions and it never leaves the NUCLEUS. RNA is like a LIBRARY or a copy center like Kinko’s.
CENTROSOMES help the cell to split itself into two new cells that are exactly the same. This lets living things grow by adding new cells. Your cells are dividing all the time! CONTRACTORS build new homes in a city and help it to grow. BANKS lend people money to build new homes and business. This also helps the city to grow.