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Nutrient Role in Bioenergetics Chapter 4 Part 2
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Bioenergetics-Glycolysis Carbohydrates primary function Energy for cellular work. Breakdown of 1 mole of glucose liberates 686 kCal of energy. 233 kCal (34%) usable The remainder dissipated as heat.
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Bioenergetics Glucose Degradation - glycolysis Occurs in two stages: 1. Anaerobic: Glucose breaks down relatively rapidly to 2 molecules of pyruvate → lactate 2. Aerobic: Pyruvate degrades further to carbon dioxide and water.
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Glycolysis Occurs in cytoplasm Enzymes ATP required as phosphate donor Glucose → glucose-6-phosphate ATP required as phosphate donor Fructose 6-phosphate
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Glycogenolysis Catabolism of muscle glycogen Glycogen phosphorylase Glucose-6-phosphate Epinephrine
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Glycolysis
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Hydrogen ions released during glycolysis NAD → NADH Additional 5 ATP molecules (ETC)
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Bioenergetics Aerobic glycolysis C 3 H 4 O 3 – pyruvic acid Rest, light to moderate levels Hydrogen + Oxygen → H 2 O
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Bioenergetics Anaerobic NAD availability Lactate formation C 3 H 4 O 3 + 2H + → C 3 H 6 O 3 Pyruvic Lactic Acid Acid
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Bioenergetics Aerobic C 3 H 4 O 3 + 2H + C 3 H 6 O 3 Pyruvic Lactic Acid Acid
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The Cori Cycle: Lactate As a Fuel Source Fig 4.16
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Bioenergetics Citric Acid Cycle (Krebs cycle). The second stage of carbohydrate breakdown Pyruvate converts to acetyl-CoA, degrades Carbon dioxide and hydrogen atoms- mitochondria Most important function Generate H ions for Electron Transport Chain (ETC)
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Bioenergetics
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Stored fat Largest source of potential energy. Supplies fatty acid molecules Energy sources for fat catabolism include: Triacylglycerol Muscle fiber - stored Lipoprotein complexes - circulating Free fatty acids - circulating
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Bioenergetics Energy metabolism – lipolysis FFA + glycerol Form intracellular triglycerides Bind with intramuscular proteins
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Bioenergetics Adenosine 3’,5’-cyclic monophosphate Cyclic AMP - Hormonal effects Epinephrine, norepinephrine, glucagon, and growth hormone
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Bioenergetics
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Glycerol Provides carbon skeletons for glucose synthesis Fatty acids Beta (ß)-oxidation converts a free fatty acid to multiple acetyl-CoA molecules. Hydrogen ions oxidized through the respiratory chain.
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Bioenergetics
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Fats in CHO Flame FA breakdown requires CHO breakdown Intermediates of citric acid cycle Oxaloacetate (pyruvate) Malate
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Bioenergetics Lipogenesis The formation of fat Cytoplasm of liver cells Excess glucose or protein not metabolized Converted into stored triacylglycerol The lipogenic process requires: ATP energy B vitamins Biotin, niacin, and pantothenic acid.
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Bioenergetics Protein Energy substrate Endurance activities Heavy trainings. Deamination: Nitrogen removed from amino acid Pyruvate FA synthesis
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Bioenergetics Protein Catabolism facilitates water loss. The amine group of protein breakdown must be eliminated. “O bligatory ” water as the waste products of protein catabolism leave the body dissolved in fluid (urine).
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Bioenergetics
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Metabolic Mill The citric acid cycle Link Food energy and the chemical energy of ATP. Intermediates Mitochondrial membrane into the cytosol to synthesize bionutrients.
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Metabolic Mill
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