The nucleus is a very important part of the cell. The nucleus holds DNA. The nucleus is small and round. It works as the cell's control center, directing everything the cell does.  

The nucleus like the mayor of a city. The mayor is in charge of the city and tells other parts of the city what to do. The nucleus has a similar job. It tells all the parts of the cell what to do.

Mitochondria are organelles, or parts of a cell. Their job is to create energy for the cell. They are ovular in shape with squiggly lines in the middle. 

They make most of the cell's supply of ATP. ATP is the same thing as energy for a cell. Their main job is to make energy. Without the mitochondria, your body would not have any energy.

The cell membrane is a thin flexible layer around the cells of all living things. It is sometimes called the plasma membrane or cytoplasmic membrane.

Its basic job is to separate the inside of cells from the outside and allows materials in and out of the cell.  In all cells, the cell membrane separates the cytoplasm inside the cell from its surroundings. In animal cells, that is all there is. Bacteria, fungi and plants have cell walls as well, which support the cell and block the passage of large molecules.

Vacuoles are membrane-bound organelles that can be found in both animals and plants. Their function is really to hold and handle waste products, and by handle, mean take in and get rid of waste. Sometimes the waste product is water, and therefore a vacuole would maintain the balance of water inside and outside a cell. Sometimes a vacuole's function is to get rid of harmful toxins. The vacuoles are quite common in plants and animals, but the vacuoles in PLANT CELLS are VERY BIG and often filled with water and in animals cells they are quite small.

A cell wall is a structural layer surrounding PLANT cells, just outside the cell membrane. It can be tough, flexible, and sometimes rigid. It provides the cell with both support and protection.

Plant cells have several structures not found in other eukaryotes. In particular, organelles called chloroplasts allow plants to capture the energy of the Sun in energy-rich molecules to give the plant energy. Chloroplasts are the site of photosynthesis.