ANATOMY

Detailed explanation-1: -Oxygen helps organisms grow, reproduce, and turn food into energy. Humans get the oxygen they need by breathing through their nose and mouth into their lungs. Oxygen gives our cells the ability to break down food in order to get the energy we need to survive.

Detailed explanation-2: -Red blood cells: Red blood cells (RBCs, also called erythrocytes; pronounced: ih-RITH-ruh-sytes) are shaped like slightly indented, flattened disks. RBCs contain hemoglobin (pronounced: HEE-muh-glow-bin), a protein that carries oxygen.

Detailed explanation-3: -No, not all cells require oxygen; in fact, some cells use a metabolic process called fermentation to produce energy, not oxygen. For example, nonoxygen-dependent (anaerobic) organisms include yeast and bacteria that are able to live in an environment with low levels of oxygen.