The Aerobic Option: Cellular RespirationVertebrates must perform aerobic cellular respiration in order to obtain enough ATP to live. This means that they need a constant supply of oxygen (a major participant in the reactions), and produce carbon dioxide as a waste. This explains the need for breathing, or physiological respiration. The reactions of aerobic respiration take place in the mitochondria, so, after glycolysis, the pyruvic acid to be processed must be transported to this organelle. We should note here that the mitochondrion (singular) is surrounded by two membranes; this creates an intermembrane space (see Figure 10.2). In addition, the inner membrane is folded to increase its surface area, and the folds are referred to as cristae. The inner, liquid portion of the mitochondria is called the matrix.