17.1.2: ATP as Fuel for Metabolism

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How Does ATP Fuel Metabolism?

All body processes - starting with breathing, making your heart pump blood, digesting food, brushing teeth, walking to the bathroom or lying in bed - require energy. The more strenuous the activity, the more energy the body needs. For example, your body burns more energy to lift a 50-pound bag of dog food than to lift a 5-pound bag of flour.1

Food is the original source of fuel for all this energy to be produced by the body. However, before your body can use the energy in the piece of bread, fruit, or cereal you ate for breakfast, it must first disassemble the macronutrients, break them into smaller compounds, and transfer their energy into the high-energy molecule adenosine triphosphate (ATP).

fig 16.4.1.jpg

Figure 9.1.1 Anaerobic versus Aerobic Metabolism. Image by Allison Calabrese / CC BY 4.0.2

Adenosine Triphosphate Is the Cell’s Energy Source

ATP is the only source of energy that cells can use directly for energy to perform any kind of work. The process of converting food to create ATP actually requires some energy (meaning, the body 'spends some ATP') to generate ATP but the net ATP production from digestion, absorption, and energy conversion is far greater than the 'initial ATP expense'.

ATP has three components: adenine, a nitrogen-containing compound; ribose, a five-carbon sugar; and three phosphate groups (which contain phosphorus and oxygen). The energy in ATP is stored in the bonds that connect the phosphate groups to each other. As Figure 9.1.2 illustrates, when the body needs energy, one of the phosphate group bonds is hydrolyzed. This releases one phosphate molecule plus a tremendous amount of energy. The new molecule that is formed is called adenosine diphosphate (ADP). At any given moment, cells only have 3–5 seconds’ worth of ATP available for immediate use; therefore, the body must continually produce ATP to provide a constant supply of energy.1

Figure 9.1.2 ATP ADP cycle. Adenosine triphosphate (ATP) is an organic chemical that provides energy for intracellular energy transfer. Adenosine diphosphate (ADP) is organic compound for metabolism in cells. Illustration Credit: Designua / Shutterstock3

Just to give you an idea: the oxidation of 1 glucose molecule generates up to 38 APT molecules.4

Important to remember: ATP is the energy source cells use to fuel metabolic reactions. Cells only have 3–5 seconds’ worth of ATP; thus, ATP must be regenerated from ADP and phosphate (which can be donated by creatine phosphate) or produced during anaerobic metabolism, which can fuel the body for no more than 1.5 minutes, or aerobic metabolism, which can continue indefinitely.1

We will review each in the upcoming segments.

Check your knowledge:

True or False: Cells use ATP to provide energy for metabolic reactions.

True or False: ATP must be regenerated from ADP and phosphate (which can be donated by creatine phosphate) or produced during anaerobic metabolism, which can fuel the body for no more than 1.5 minutes, or aerobic metabolism, which can continue indefinitely.

Contributors

Claudia Kelley

References & Links

Blake, J. S., Munoz, K. D., & Volpe, S. (2019). Nutrition: From Science to You (4th ed.). Pearson.
https://med.libretexts.org/Under_Con...A_Fuel_Sources
https://www.news-medical.net/health/...etabolism.aspx
Gropper SS, Smith JL, Groff JL. (2016) Advanced nutrition and human metabolism (7th ed.). Cengage.
ATP-PCr system in The Oxford Dictionary of Sports Science & Medicine (3)
Sousa, A., Ribeiro, J. & Figueiredo, P. (2019). Physiological Demands in Sports Practice. 10.1007/978-3-030-10433-7_4.