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PowerPoint® Lecture Slide Presentation by Vince Austin Human Anatomy & Physiology FIFTH EDITION Elaine N. Marieb Chapter 25 Nutrition, Metabolism, and Body Temperature Regulation Part A Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Nutrition • Nutrient – a substance that promotes normal growth, maintenance, and repair • Major nutrients – carbohydrates, lipids, and proteins • Other nutrients – vitamins and minerals (and technically speaking, water) • Grains, fruits, vegetables, meats and fish, and milk products Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Nutrition Figure 25.1 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Carbohydrates • Complex carbohydrates (starches) are found in bread, cereal, flour, pasta, nuts, and potatoes • Simple carbohydrates (sugars) are found in soft drinks, candy, fruit, and ice cream • Glucose is the molecule ultimately used by body cells to make ATP • Neurons and RBCs rely almost entirely upon glucose to supply their energy needs • Excess glucose is converted to glycogen or fat and stored Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Carbohydrates • The minimum amount of carbohydrates needed to maintain adequate blood glucose levels is 100 grams per day • Starchy foods and milk have nutrients such as vitamins and minerals in addition to complex carbohydrates • Refined carbohydrate foods (candy and soft drinks) provide energy sources only and are referred to as “empty calories” Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Lipids • The most abundant dietary lipids, triglycerides, are found in both animal and plant foods • Essential fatty acids – linoleic and linolenic acid, found in most vegetables, must be ingested • Dietary fats: • Help the body to absorb vitamins • Are a major energy fuel of hepatocytes and skeletal muscle • Are a component of myelin sheaths and all cell membranes Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Lipids • Fatty deposits in adipose tissue provide: • A protective cushion around body organs • An insulating layer beneath the skin • An easy-to-store concentrated source of energy • Prostaglandins function in: • Smooth muscle contraction • Control of blood pressure • Inflammation • Cholesterol stabilizes membranes and is a precursor of bile salts and steroid hormones Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Lipids: Dietary Requirements • Higher for infants and children than for adults • The American Heart Association suggests that: • Fats should represent less than 30% of one’s total caloric intake • Saturated fats should be limited to 10% or less of one’s total fat intake • Daily cholesterol intake should not exceed 200 mg Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Proteins • Complete proteins that meet all the body’s amino acid needs are found in eggs, milk, milk products, meat, and fish • Incomplete proteins are found in legumes, nuts, seeds, grains, and vegetables • Proteins supply: • Essential amino acids, the building blocks for nonessential amino acids • Nitrogen for nonprotein nitrogen-containing substances • Daily intake should be approximately 0.8g/kg of body weight Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Proteins: Synthesis and Hydrolysis • All-or-none rule • All amino acids needed must be present at the same time for protein synthesis to occur • Adequacy of caloric intake • Protein will be used as fuel if there is insufficient carbohydrate or fat available Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Proteins: Synthesis and Hydrolysis • Nitrogen balance • The rate of protein synthesis equals the rate of breakdown and loss • Positive – synthesis exceeds breakdown (normal in children and tissue repair) • Negative – breakdown exceeds synthesis (e.g., stress, burns, infection, or injury) • Hormonal control • Anabolic hormones accelerate protein synthesis Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Vitamins • Organic compounds needed for growth and good health • They are crucial in helping the body use nutrients and often function as coenzymes • Only vitamins D, K, and B are synthesized in the body; all others must be ingested • Water-soluble vitamins (B-complex and C) are absorbed in the gastrointestinal tract • B12 additionally requires gastric intrinsic factor to be absorbed Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Vitamins • Fat-soluble vitamins (A, D, E, and K) bind to ingested lipids and are absorbed with their digestion products • Vitamins A, C, and E also act in an antioxidant cascade Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Minerals • Seven minerals are required in moderate amounts • Calcium, phosphorus, potassium, sulfur, sodium, chloride, and magnesium • Dozens are required in trace amounts • Minerals work with nutrients to ensure proper body functioning • Calcium, phosphorus, and magnesium salts harden bone Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Minerals • Sodium and chloride help maintain normal osmolarity, water balance, and are essential in nerve and muscle function • Uptake and excretion must be balanced to prevent toxic overload Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Metabolism • Metabolism – all chemical reactions necessary to maintain life • Cellular respiration – food fuels are broken down within cells and some of the energy is captured to produce ATP • Anabolic reactions – synthesis of larger molecules from smaller ones • Catabolic reactions – hydrolysis of complex structures into simpler ones Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Metabolism • Enzymes shift the high-energy phosphate groups of ATP to other molecules • These phosphorylated molecules are activated to perform cellular functions Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Stages of Metabolism • Energy-containing nutrients are processed in three major stages • Digestion – breakdown of food; nutrients are transported to tissues • Anabolism and formation of catabolic intermediates where nutrients are: • Built into lipids, proteins, and glycogen • Broken down by catabolic pathways to pyruvic acid and acetyl CoA • Oxidative breakdown – nutrients are catabolized to carbon dioxide, water, and ATP Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Stages of Metabolism Figure 25.3 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Oxidation-Reduction Reaction • Oxidation occurs via the gain of oxygen or the loss of hydrogen • Whenever one substance is oxidized, another substance is reduced • Oxidized substances lose energy • Reduced substances gain energy • Coenzymes act as hydrogen (or electron) acceptors • Two important coenzymes are nicotinamide adenine dinucleotide (NAD+) and flavin adenine dinucleotide (FAD) Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Mechanisms of ATP Synthesis: Substrate-Level Phosphorylation • High-energy phosphate groups are transferred directly from phosphorylated substrates to ADP • ATP is synthesized via substrate level phosphorylation in glycolysis and the Krebs cycle Figure 25.4a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Mechanisms of ATP Synthesis: Oxidative Phosphorylation • Uses the chemiosmotic process whereby the movement of substances across a membrane is coupled to chemical reactions • Is carried out by the electron transport proteins in the cristae of the mitochondria • Nutrient energy is used to pump hydrogen ions into the intermembrane space • A steep diffusion gradient across the membrane results • When hydrogen ions flow back across the membrane through ATP synthase, energy is captured and attaches phosphate groups to ADP (to make ATP) Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Mechanisms of ATP Synthesis: Oxidative Phosphorylation Figure 25.4b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Carbohydrate Metabolism • Since all carbohydrates are transformed into glucose, it is essentially glucose metabolism • Oxidation of glucose is shown by the overall reaction: C6H12O6 + 6O2 6H2O + 6CO2 + 36ATP + heat • Occurs in three pathways • Glycolysis • Krebs cycle • The electron transport chain and oxidative phosphorylation Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Carbohydrate Metabolism Figure 25.5 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Glycolysis • A three-phase pathway in which: • Glucose is oxidized into pyruvic acid • NAD+ is reduced to NADH + H+ • ATP is synthesized by substrate-level phosphorylation • Pyruvic acid: • Moves on to the Krebs cycle in an aerobic pathway • Is reduced to lactic acid in an anaerobic environment Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Glycolysis Figure 25.6 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Glycolysis: Phase 1 and 2 • Sugar activation • Two ATP molecules activate glucose into fructose-1,6-diphosphate • Sugar cleavage • Fructose-1,6-diphosphate is cleaved into two 3carbon isomers • Dihydroxyacetone phosphate • Glyceraldehyde 3-phosphate Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Glycolysis: Phase 3 • Oxidation and ATP formation • The 3-carbon sugars are oxidized (reducing NAD+) • Inorganic phosphate groups (Pi) are attached to each oxidized fragment • The terminal phosphates are cleaved and captured by ADP to form four ATP molecules • The final products are: • Two pyruvic acid molecules • Two reduced NAD+ (NADH + H+) molecules • A net gain of two ATP molecules Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings