Lecture 2-7

Lecture 2-7 - Exercise Metabolism I. Biological Energy...

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Exercise Metabolism I. Biological Energy Systems a. Three basic energy systems exist in muscle cells to replenish ATP: i. The phosphagen system ii. Glycolysis iii. The oxidative system II. Phosphagen System a. Provides ATP primarily for short-term, high-intensity activities (e.g., resistance training and sprinting) and is active at the start of all exercise regardless of intensity III. Phosphagen System a. The body does not store enough ATP for exercise. b. Some ATP is needed for basic cellular function. c. The phosphagen system uses the creatine kinase reaction to maintain the concentration of ATP i. replenishes ATP rapidly d. Control of the Phosphagen System i. Law of mass action: The concentrations of reactants or products (or both) in solution will drive the direction of the reactions IV. Glycolysis a. breakdown of carbohydrates—either glycogen stored in the muscle or glucose delivered in the blood —to resynthesize ATP V. Glycolysis a. end result (pyruvate) may proceed in one of two directions: i. 1) Pyruvate can be shuttled into the mitochondria to undergo TCA cycle 1. ATP resynthesis rate is slower, but it can occur for a longer duration if the exercise intensity is low enough 2. aerobic glycolysis or slow glycolysis ii. 2) Pyruvate can be converted into lactate 1. Anaerobic glycolysis VI. Glycolysis and the Formation of Lactate a. Pyruvate is converted into lactate
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i. The end result is not lactic acid ii. Lactate is not the cause of fatigue 1. Oxidation of ATP causes fatigue b. Cori Cycle i. Lactate can be transported in the blood to the liver, where it is converted to glucose during gluconeogenesis c. Lactacte can be oxidixed to pyruvate in muscle VII. Key Term a. lactate threshold (LT): The exercise intensity or relative intensity at which blood lactate begins an abrupt increase above the baseline concentration. VIII. Figure 2.4 a. IX. Lactate Threshold and Onset of Blood Lactate a. LT begins at 50% to 60% of maximal oxygen uptake in untrained individuals. b. It begins at 70% to 80% in trained athletes. c. OBLA is a second increase in the rate of lactate accumulation i. occurs at higher relative intensities of exercise ii. occurs when the concentration of blood lactate reaches 4 mmol/L. X. Fat Oxidation a. Oxidative (aerobic) system is the primary source of ATP at rest and during low-intensity activities b. Uses primarily carbohydrates and fats as substrates XI. Beta Oxidation a. Triglycerides broken down by hormone-sensitive lipase
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i. releases free fatty acids into the blood 1. enter muscle fibers 2. Some free fatty acids come from intramuscular sources b. Free fatty acids undergo beta oxidation i. Results in formation of acetyl-CoA and hydrogen protons ii. The acetyl-CoA enters the TCA cycle iii. The hydrogen atoms are carried by NADH and FADH 2 to the electron transport chain. XII.
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This note was uploaded on 04/22/2010 for the course KIN 3513 taught by Professor Porter during the Spring '08 term at LSU.

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Lecture 2-7 - Exercise Metabolism I. Biological Energy...

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