Enter the mitochondria. Referred to as ‘organelles,’ mitochondria are oblong or oval in shape and have a double membrane. Found in both animal and plant calls, the numbers of each within a cell varies. For example, mature red blood cells contain no mitochondria at all, likely because red blood cells need all the room possible in the cytoplasm (all the material inside a given cell outside the nucleus) for hemoglobin molecules that transport oxygen to the brain and body. Muscle cells may contain hundreds or thousands of mitochondria. Think of mitochondria as energy factories or energy generating plans, generating energy in the form of ATP (adenosine triphosphate) a coenzyme that cells use for energy storage. Without sufficient ATP the brain and body tend to malfunction in some way or other. More tomorrow.