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By studying this chapter, you should be able to do the following:

  1. Discuss the function of the cell membrane, nucleus, and mitochondria.

  2. Define the following terms: (1) endergonic reactions, (2) exergonic reactions, (3) coupled reactions, and (4) bioenergetics.

  3. Describe the role of enzymes as catalysts in cellular chemical reactions.

  4. List and discuss the nutrients that are used as fuels during exercise.

  5. Describe the structure and function of ATP in the cell.

  6. Discuss the biochemical pathways involved in anaerobic ATP production.

  7. Describe the aerobic production of ATP.

  8. Describe how the metabolic pathways involved in bioenergetics are regulated.

  9. Discuss the interaction between aerobic and anaerobic ATP production during exercise.

  10. Identify the enzymes that are considered rate limiting in glycolysis and the citric acid cycle.


Cell Structure

Biological Energy Transformation

  • Cellular Chemical Reactions

  • Oxidation–Reduction Reactions

  • Enzymes

Fuels for Exercise

  • Carbohydrates

  • Fats

  • Proteins

High-Energy Phosphates


  • Anaerobic ATP Production

  • Aerobic ATP Production

Aerobic ATP Tally

Efficiency of Oxidative Phosphorylation

Control of Bioenergetics

  • Control of ATP-PC System

  • Control of Glycolysis

  • Control of Citric Acid Cycle and Electron Transport Chain

Interaction Between Aerobic/Anaerobic ATP Production

Key Terms


activation energy

adenosine diphosphate (ADP)

adenosine triphosphate (ATP)




ATP-PC system

beta oxidation


cell membrane

chemiosmotic hypothesis

citric acid cycle (also called the Krebs cycle)

coupled reactions


electron transport chain

endergonic reactions


exergonic reactions

flavin adenine dinucleotide (FAD)






inorganic phosphate (Pi)

isocitrate dehydrogenase

Krebs cycle (also called citric acid cycle)




molecular biology

nicotinamide adenine dinucleotide (NAD+)




oxidative phosphorylation

phosphocreatine (PC)

phosphofructokinase (PFK)


Thousands of chemical reactions occur throughout the body during each minute of the day. Collectively, these reactions are called metabolism. Metabolism is broadly defined as the total of all cellular reactions and includes chemical pathways that result in the synthesis of molecules (anabolic reactions), as well as the breakdown of molecules (catabolic reactions).

Because energy is required by all cells, it is not surprising that cells possess chemical pathways that are capable of converting foodstuffs (i.e., fats, proteins, carbohydrates) into a biologically usable form of energy. This metabolic process is termed bioenergetics. For you to run, jump, or swim, skeletal muscle cells must be able to continuously extract energy from food nutrients. Indeed, in order to continue to contract, muscle cells must have a continuous source of energy. Given the importance of cellular energy production during exercise, it is essential that students of exercise physiology develop a thorough understanding of bioenergetics. Therefore, this chapter will introduce both general and specific concepts associated with bioenergetics.


Cells were discovered in the seventeenth century by the English scientist Robert Hooke. Advancements in the microscope over the past 300 years have led to improvements in our understanding of cell structure ...

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