Ch. 3.3 - Glycolysis & Lactate PDF

KIN 474 – Dr. Haff 4th ed. – Ch. 3.3 Hudson (p. 50-55) Glycolysi 1  Biological Energy Systems Glycolysis – The breakdown of carbohydrates— either glycogen stored in the muscle or glucose delivered in the blo...

KIN 474 – Dr. Haff 4th ed. – Ch. 3.3 Hudson (p. 50-55) Glycolysi 1  Biological Energy Systems Glycolysis – The breakdown of carbohydrates— either glycogen stored in the muscle or glucose delivered in the blood—to resynthesize ATP – Series of 10 enzymatic reactions designed to yield ATP or to send electron carriers to the ETC 2 2 Fig. 3.2. Haff et al. 2016. Essentials of Strength… Human Kinetics 3  Fast Glycolysis Hexokinase traps glucose in the cell where it can either go through glycolysis or be stored as glycogen Overall process controlled by the rate-limiting enzyme, phosphofructokinase (PFK) The end result of glycolysis (pyruvate) may proceed in one of two directions: 1) Pyruvate can be converted to lactate. – This process is sometimes called anaerobic glycolysis (or fast glycolysis). – ATP resynthesis occurs at a faster rate but is limited in duration. Very important for high-intensity exercise – Only yields 2 ATP (if from glucose) or 3 ATP (if from 4 glycogen) 4 Fig. 3.2. Haff et al. 2016. Essentials of Strength… Human Kinetics 5  Slow Glycolysis The end result of glycolysis (pyruvate) may proceed in one of two directions (continued): 2) Pyruvate can be shuttled into the mitochondria. – This process is often referred to as aerobic glycolysis (or slow glycolysis). – In the mitochondria, pyruvate goes through the Krebs cycle and electron transport chain – Only half as fast as “fast” glycolysis, but provides more ATP – Most important for endurance exercise – Only yields 32 ATP (if from glucose) or 33 ATP (if 6 from glycogen) 6  Glycolysis & Lactate So why make lactate with fast glycolysis and not use the mitochondria to get more ATP? – SPEED! You need to make ATP very quickly to meet the demand in high- intensity exercise Making lactate helps to buffer excess acidity created during high-intensity exercise Mitochondria normally buffers H+ (acidity) in the ETC, but is too slow in high-intensity exercise. – Conversion of pyruvate to lactate is 7 7  Lactate Myths  Metabolic acidosis – exercise- induced decrease in pH  May be responsible for much of the fatigue after high-intensity exercise  Results from accumulation of H+, not lactic acid Lactate is not the cause of fatigue.  Lactate concentration is a balance between lactate production and removal.  Lactate production increases with exercise intensity and is dependent upon fiber type  Light activity during the postexercise period 8 8 can increase lactate clearance rates.  Review Questions  Explain the purpose and identify the enzymes of the 2 steps of glycolysis  What are the differences in converting pyruvate to lactate or having it enter the mitochondria?  Name the enzyme that converts pyruvate to lactate  Why is glycogen preferred over glucose for glycolysis during exercise?  Explain the purposes of generating lactate 9 9  Figure & Notes References  Haff & Triplett. Essentials of Strength Training & Conditioning, 4th edition. Human Kinetics, 2016.  Kenney, Wilmore, Costill. Physiology of Sport & Exercise, 6th edition. Human Kinetics, 2015.  McCardle, Katch, Katch. Exercise Physiology: Nutrition, Energy, and Human Performance, 8th edition. Wolters Kluwer Health, 2014. 1 10