In this topic you will learn about how knowing about cells can help you plan your meals.

Animals have many different kinds of cells in their bodies. The cells have smaller parts inside. These cells have parts in common. Each part has a special function. All cells have an outer covering called a cell membrane. The cell membrane gives the cell shape and helps control the movement of materials in and out of the cell. The nucleus is the densest part of a cell and it controls a cell's activities. The nucleus is the largest, most visible part of the cell and is separated from the cytoplasm by its own membrane.

Long strands called chromosomes can be found in the nucleus. They are like blueprints of the cell. They store directions for cell activities. They transfer the directions to the next generation of cells.

Cytoplasm is the gel-like substance inside the cell membrane where most of the cell activities occur. The cytoplasm contains a large amount of water. It also contains chemicals and other cell structures that carry out special jobs.

A rod-shaped structure that supplies the cell with energy is called the mitochondrion. This structure is often referred to as the "powerhouses" of the cell. It packages and secretes materials containing energy which can be used by cells. A vacuole is a sac-like storage space in a cell. It stores wastes (prior to removal), as well as food.

Both plant and animal cells have several structures in common. Plant cells contain some structures that are not found in animal cells. Plant cells contain cell walls and chloroplasts. The cell wall is a stiff covering outside the cell membrane of a plant cell. It protects and supports the cell. Water and other substances pass through the cell wall to the interior of the cell. A chloroplast is a green structure in a plant cell where food is produced. Chloroplasts are green because they contain a green pigment called chlorophyll. They are found in plant leaves and stems.

Your cells are made of chemical elements including carbon, hydrogen, oxygen and nitrogen. These elements are joined together and form compounds. Foods are made up of compounds. One group of carbon compounds are called carbohydrates, which supply energy for cell activities. You get carbohydrates from foods such as fruits, bread, spaghetti, and potatoes. Proteins are compounds needed for cell growth and repair. Proteins-found in milk, eggs, fish, beans, and meat-provide materials for cells to build proteins.

You can use what you know about the composition of your body to help you plan nutritional and healthful meals. A healthful body weight is based on nutritional meals, daily physical activity, and rest.