Aerobic and anaerobic respiration are the two types of cellular respiration that occur in the cells of living organisms. Aerobic respiration requires oxygen, while anaerobic respiration can occur in the absence of oxygen.
Cellular respiration pertains to the series of metabolic pathways wherein glucose molecules are broken down to generate adenosine triphosphate, or ATP, which is a high-energy molecule that drives vital life processes.
Aerobic respiration is divided into three major steps: glycolysis, Krebs cycle and electron-transport chain. Glycolysis is the only aerobic pathway that can also occur without an oxygen supply. Anaerobic microorganisms generally use glycolysis to produce ATP.
Humans are also capable of anaerobic respiration. Low levels of oxygen in the body due to strenuous activities force the cells to produce lactic acid in exchange for extra energy.