And this will be the focus of this lecture. Now, before we actually discuss how increasing or decreasing the temperature effect hemoglobin, let's discuss where this increase in temperature actually comes from. So, inside the cells of our exercising tissue, these exercising cells are carrying out more metabolic processes such as cellular respiration. And what that means is more thermal energy is produced as a byproduct. Thermal energy is energy that cannot be used to do any useful work. And so what the cells actually do is they release that energy into the blood plasma of the nearby capillary.