Where do they get this energy?

–Karthik Gurumurthy

Animals need a constant supply of energy to move, grow and carry out all their activities. Where does that energy come from? It is made in the cells- the animal’s energy factories.

Food, water and oxygen are converted to energy, chemicals and other useful materials inside your cells. When you eat, drink and breathe, you are actually feeding the billions of cells that make up your body. When you feel hungry, it is really your cells that are hungry. When you feel thirsty, your cells need more water.

Nutrients are the substances in food that cells use to do their work. Each type of nutrient has a special job. Carbohydrates are the main fuel that cells use to make energy. Protein provides the building materials to make muscles, bones, teeth, hair, and other body structures. Fat is second kind of fuel. If the body does not have enough carbohydrates, cells will “burn” fat to make energy. Vitamins and minerals help make certain chemicals and structures in the body and assist in repairing injuries.

Just as organs do the work of the body, each cell contains organelles (little organs) that do the work of the cell. For example, the nucleus, the cell’s “brain”, directs the cell’s activities. Lysosomes process nutrients. Mitochondria convert water, oxygen and nutrients into energy.

Organelles are suspended in a jelly like substance called cytoplasm. The cytoplasm is surrounded by a thin covering, called the cell membrane. A cell’s membrane has tiny holes for water and oxygen to pass through. However, nutrients and most other materials have to pass through special “gates”. These gates are the security guards of the cell and protect it from harmful bacteria and viruses that might make an animal sick. Waste from cells, including carbon dioxide and unused nutrients, leaves the cell through the membrane as well.