Why is the pO2 elevated? Which macronutrients require oxygen for their catabolism?

The pO2, or partial pressure of oxygen, can be elevated for several reasons. This could be due to hyperventilation, where the body is taking in more oxygen than usual, or due to an increase in the amount of oxygen in the environment, such as with supplemental oxygen therapy. It could also be due to certain medical conditions that affect the body's ability to regulate oxygen levels.

As for the second part of your question, all macronutrients - carbohydrates, proteins, and fats - require oxygen for their catabolism. This is because catabolism is the process of breaking down these macronutrients to produce energy, and this process requires oxygen. Specifically, oxygen is used in the final steps of cellular respiration, a process that breaks down glucose (from carbohydrates), amino acids (from proteins), and fatty acids (from fats) to produce ATP, the body's main energy currency.