Nutrition and Metabolism Dietary Sources of Major Nutrients Basics of Cellular Respiration Metabolism of Carbos, Fats, and Protein Central Role of the Liver in Digestion/Metabolism Cholesterol and Lipid Transport Absorptive and Postabsorptive States Developmental Aspects of Metabolism

Sources of Nutrients in the Diet Macronutrients: Carbohydrates, Protein, Lipids, H2O Micronutrients: Vitamins, Minerals Major source of vitamins & minerals Major source of carbohydrates & B vitamins Major protein source some vitamins Major source of minerals and vitamins A and D, some protein Major source of lipids and fat soluble vitamins A,D,E, K

potatoes, pasta, sweets: use sparingly Red meat, butter: use sparingly White rice, white bread, potatoes, pasta, sweets: use sparingly Dairy or calcium supplement: 1–2 servings Fish, poultry, eggs: 0–2 servings Nuts, legumes: 1–3 servings Vegetables in abundance Fruits: 2–3 servings Whole-grain foods at most meals Plant oils at most meals Daily excercise and weight control (b) Healthy eating pyramid Figure 24.1b

Nutrition and Metabolism Dietary Sources of Major Nutrients Basics of Cellular Respiration Metabolism of Carbos, Fats, and Protein Central Role of the Liver in Digestion/Metabolism Cholesterol and Lipid Transport Absorptive and Postabsorptive States Developmental Aspects of Metabolism

Oxidation-Reduction is Important in Energy Production In biological systems, the electrons are often associated with hydrogen atoms. Biological oxidations are often dehydrogenations. Or FAD+ FADH2 Sugars, amino acids, fatty acids Figure 5.10 5

The Energy Stored in ATP Can Be Used to Perform Work in the Cell The energy released by ATP breaking down into ADP and P can power a variety of needs in the cell ADP Energized ATP: P ADP Discharged ATP: P Powering the synthesis of molecule Z by coupling oxidation to reduction: X Y + Z 6

Metabolic Pathways Involved in Cellular Respiration An oxidation of glucose to reduce ADP to ATP 34 Overall Equation for Cellular Respiration

Aerobic Cellular Respiration C6H12O6 + O2 CO2 + H2O + 34ATP sugar oxygen carbon dioxide water usable energy CO2 glucose CO2 NAD NADH Glycolysis 2 ATP (substrate-level phosphorylation) Cell membrane 2 pyruvates CO2 4 ATP (substrate-level phosphorylation) Linking Step mitochondrion Acetyl CoA Krebs Cycle Electron Transport Chain and ATP Synthase O2 ATP fuels construction/synthesis reactions inside the cell H 2O 30 ATP (oxidative phosphorylation) ATP Synthase

Nutrition and Metabolism Dietary Sources of Major Nutrients Basics of Cellular Respiration Metabolism of the Three Macronutrients: Carbohydrates, Fats, and Protein Central Role of the Liver in Digestion/Metabolism Cholesterol and Lipid Transport Absorptive and Postabsorptive States Developmental Aspects of Metabolism

Fat Metabolism Fat metabolism handled mostly by the liver Some fats used to make ATP Used to synthesize lipoproteins, thromboplastin, and cholesterol Release breakdown products to the blood in liver Body cells remove fat and cholesterol to build membranes, steroid hormones, adipose cells, and myelin sheaths acetone and acetoacetic acid = ketosis/acid-osis Oxidation of Fats (ß-Oxidation) for ATP Fat catabolism yields 9 kcal per gram (vs 4 kcal per gram of carbohydrate or protein) Fats must first be broken down to acetic acid, then in mito. to H2O, CO2, and ATP Ketones (acetoacetic acid and acetone can accumulate, producing acidosis/ketosis)

Protein Metabolism urea deamination

Three Macronutrients Used for ATP Production Stage 1 Digestion in GI tract lumen to absorbable forms. Transport via blood to tissue cells. PROTEINS CARBOHYDRATES FATS Amino acids Glucose and other sugars Glycerol Fatty acids Stage 2 Anabolism (incorporation into molecules) and catabolism of nutrients to form intermediates within tissue cells. Proteins Glucose Glycogen Fats NH3 Pyruvic acid Acetyl CoA Stage 3 Oxidative breakdown of products of stage 2 in mitochondria of tissue cells. CO2 is liberated, and H atoms removed are ultimately delivered to molecular oxygen, forming water. Some energy released is used to form ATP. Krebs cycle Infrequent CO2 O2 Oxidative phosphorylation (in electron transport chain) H H2O Catabolic reactions Anabolic reactions Figure 24.3

Nutrition and Metabolism Dietary Sources of Major Nutrients Basics of Cellular Respiration Metabolism of Carbos, Fats, and Protein Central Role of the Liver in Digestion/Metabolism Cholesterol and Lipid Transport Absorptive and Postabsorptive States Developmental Aspects of Metabolism

Role of the Liver in Metabolism Produces blood proteins (albumin, clotting proteins) and lipoproteins Degrades hormones

Liver Modifications on Glucose Levels Glycogenesis (making glycogen) Glucose molecules are converted to glycogen Glycogen molecules are stored in the liver Glycogenolysis (breaking glycogen) Glucose is released from the liver after conversion from glycogen Gluconeogenesis (rebuilding glucose) Glucose is produced from amino acids and glycerol Protects against damaging effects of hypoglycemia

Roles of Cholesterol in the Body Keeping membranes fluid Vitamin D synthesis Steroid Hormone Synthesis

Cholesterol Transport Cholesterol and fatty acids cannot freely circulate in the bloodstream They are transported by chylomicron lipoproteins (lipid-protein complexes) Low-density lipoproteins (LDLs) transport cholesterol to body cells; are increased by dietary saturated and trans-fat Triglycerides broken down by fat and muscle tissue (lipoprotein lipase) into fatty acids and glycerol High-density lipoproteins (HDLs) transport from body cells to the liver for breakdown; are increased by exercise, and limited coffee, smoking, and saturated fats/trans fats Healthy Ratios in the Blood Total Cholesterol/HDL < 5 LDL/HDL < 2.5 Total cholesterol (mg/dL) Under 200    -   desirable  200-239       -   borderline high Over 240      -   high LDL cholesterol (mg/dL) Below 100    -   optimal 100-129        -   near optimal 130-159        -   borderline high 160-189        -   high Above 190    -   very high HDL cholesterol (mg/dL) Below 40      -    low 60 or above   -    high 

Nutrition and Metabolism Dietary Sources of Major Nutrients Basics of Cellular Respiration Metabolism of Carbos, Fats, and Protein Central Role of the Liver in Digestion/Metabolism Cholesterol and Lipid Transport Absorptive and Postabsorptive States Developmental Aspects of Metabolism

Absorptive and Postabsorptive States Absorptive (fed) state During and shortly after eating; absorption of nutrients Muscle and fat tissue: lipoprotein lipase hydrolyzes lipids of chylomicrons in muscle and fat tissues; most glycerol and fatty acids are converted to triglycerides for storage Liver: Excess amino acids are deaminated and used for ATP synthesis or stored as fat in the liver Insulin facilitates glucose uptake, glycogenesis, triglyceride genesis, and protein synthesis Postabsorptive (fasting) state When the GI tract is empty; energy sources are supplied by breakdown of reserves Liver: lipolysis, glycerol then fuels glycogenolysis Skeletal muscle: glycogenolysis; protein catabolism if starving Fat tissue: lipolysis tissues and the liver Glucagon facilitates glycogenolysis and gluconeogenesis in the liver, fat tissue lipolysis

Developmental Aspects of the Digestive System Fetal Development The alimentary canal is a continuous tube by the fifth week of development Digestive glands bud from the mucosa of the alimentary tube The developing fetus receives all nutrients through the placenta Birth and Infancy In newborns, feeding must be frequent, peristalsis is inefficient, and vomiting is common Congenital conditions include cleft palate, phenylketonuria, tracheoesophageal fistula Teething (eruption of teeth) begins around age six months Metabolism decreases with old age Middle age digestive problems Ulcers Gall bladder problems Old Age Fewer digestive juices Peristalsis slows Diverticulosis and cancer are more common brain damage and retardation in infancy PKU Tracheoesophageal Fistula

Nutrition and Metabolism Dietary Sources of Major Nutrients Basics of Cellular Respiration Metabolism of Carbos, Fats, and Protein Central Role of the Liver in Digestion/Metabolism Cholesterol and Lipid Transport Absorptive and Postabsorptive States Developmental Aspects of Metabolism