The food we eat gives our cells energy to carry out various functions, such as growth and division. How do cells convert food into a form of energy that they can understand and use? The answer is metabolism, which is the whole web of metabolic pathways that occur in a cell at any given time. Metabolic pathways string together individual chemical reactions, where the product of an earlier reaction serves as the reactant for the next.
Some metabolic pathways are catabolic. Catabolic processes break down large macromolecules into smaller pieces (think catabolism ~ cannibalism), and usually release energy in the form of adenosine triphosphate (ATP). On the other hand, anabolic processes extract energy from ATP and use it to build larger, more complex macromolecules, where the energy is stored.
Carbohydrates (like glucose) are our cell's preferred fuel source. There are two central pathways our cells use to catabolize carbohydrates. The first is called aerobic cellular respiration, which occurs in the presence of oxygen to produce an abundance of ATP. The other type is called anaerobic cellular respiration, which creates a smaller amount of ATP when oxygen is not readily accessible.
In addition to learning the details of each pathway, we will also learn about a few funky methods our cells use to produce energy from different fuels, such as fats and proteins. First, let’s learn more about bio-thermodynamics.