++
Learning Objectives
After studying this chapter, the reader should be able to:
6.1 Trace the pathway of a food starting with consumption and ending with usable energy.
6.2 Outline the metabolic pathways including the phosphagen system, anaerobic glycolysis, aerobic glycolysis, and fatty acid oxidation as they relate to exercise performance.
6.3 Explain how energy is stored in the skeletal muscles and other tissues, and how other nutrients are delivered via the digestion and absorption system.
6.4 Apply energy metabolism to design of nutrition strategies for active individuals and populations.
++
KEY TERMS
aerobic respiration The 10-step metabolic process of breaking glucose down to intermediate pyruvate, which is converted to acetyl-CoA and enters the citric acid cycle. Occurs in the mitochondria and cytoplasm in the presence of oxygen; produces a net 36 ATP.
anaerobic respiration The 10-step metabolic process of breaking glucose down to intermediate pyruvate and then lactic acid; occurs in the cytoplasm of cells; produces a net 2 ATP.
anaerobic threshold Point in exercise when lactate accumulation begins. Also known as lactate threshold or ventilatory threshold.
beta oxidation The process in which carbon fragments are removed from the fatty acid. These carbon molecules produce acetyl CoA, which enters the citric acid cycle and electron transport chain.
bioenergetics The process of studying the capture, conversion, and use of energy from ATP.
cardiac output (Q) The volume of blood pumped through the heart per minute (mL blood/min); calculated as stroke volume (mL blood/beat) x heart rate (beat/min).
citric acid cycle A metabolic pathway involved in the chemical conversion of carbohydrates, fats, and proteins into carbon dioxide and water to generate a form of usable energy. Also known as Krebs cycle and tricarboxylic acid cycle.
creatine phosphate An important source of stored energy; its breakdown to creatine plus a high-energy phosphate can rapidly fuel the first 5 to 10 seconds of exercise.
cross-bridge cycle The process whereby a series of molecular actions cause myosin and actin to interact and produce muscle contraction.
electron-transport chain The process of stripping NADH and FADH of their hydrogen molecules through a series of chemical reduction-oxidation reactions, which ultimately powers the conversion of ADP plus Pi to ATP and provides energy to the working cell.
excess post-exercise oxygen consumption (EPOC) The elevated oxygen consumption after high-intensity exercise has stopped.
flavin adenine dinucleotide (FADH) A hydrogen- carrying molecule that enters the electron transport chain to produce 2 ATPs per molecule of FADH.
gluconeogenesis The production of glucose from precursors in the liver.
glycolysis The process through which glucose is converted to pyruvate.
Krebs cycle See citric acid cycle.
lactate A salt of lactic acid produced in the body.
lactate threshold Point in exercise when lactate accumulation begins. Also known as anaerobic threshold or ventilatory threshold.
lactic acid A metabolic byproduct of anaerobic glucose metabolism.
lipogenesis The production of fat from excess carbohydrate, protein, or fat that is consumed ...