BIOL 244 Chapter 24: NutritionLecture 5 (September 4) Nutrition: substance in food that promotes normal growth maintenance, & repair Major nutrients: carbohydrates, lipids, & proteins (energy-yielding nutrients) Others: vitamins and minerals and water Carbohydrates Starch in grains and vegetables Complex carbohydrates Sugars in fruits, sugarcane, sugar beets, honey and milk Includes monosaccharides and disaccharides Insoluble fiber: cellulose in vegetables; provides roughage Uses: Glucose is the immediate fuel used by cells to make ATP (cellular respiration: glycolysisglucose splits into 2 pyruvates)- Neurons and RBCs rely almost entirely upon glucose  Excess glucose is converted to glycogen or fat and stored Dietary requirements Minimum 100 g/day to maintain adequate blood glucose levels Lipids Triglycerides Saturated fats in meat, dairy foods, and tropical oils Unsaturated fats in seeds, nuts, olive oil, and most vegetable oils Cholesterol in egg yolk, meats, shell fish, & diary Uses: Help absorb fat-soluble vitamins Major fuel of hepatocytes and skeletal muscle Phospholipids are essential in all cell membranes and myelin sheaths for neurons Functions of fatty deposits (adipose tissue) Protective cushions around body organs, Insulating layer beneath the skin Concentrated source of energy Functions of cholesterol Stabilizes membranes Precursor of bile salts and steroid hormones Proteins Eggs, milk, fish, and most meats contain complete proteins Legumes, nuts, and cereals contain incomplete proteins (lack some essential amino acids) Legumes and cereals together contain all essential amino acids  Uses: Structural materials: keratin, collagen, elastin, muscle proteins Most functional molecules: enzymes, some hormones Use of amino acids All amino acids needed must be present for protein synthesis to occur adequacy of caloric intake Protein will be used as fuel if there is insufficient carbohydrate or fat available Metabolism: biochemical reactions inside cells involving nutrients 2 types of reactions Anabolism: synthesis of large molecules from small ones Catabolism: hydrolysis of complex structures to simpler ones Cellular respiration: catabolism of food fuels and capture of energy to form ATP in cells Enzymes shift high-energy phosphate groups of ATP to other molecules (phosphorylation) Phosphorylated molecules are activated to perform cellular functions Stages Digestion, absorption and transport to tissues Cellular processing in cytoplasm- Synthesis of lipids, proteins, and glycogen, or- Catabolism into intermediates (process of Glycolysis)  Oxidative breakdown of intermediates into CO2, water, and ATP - Occurs in mitochondria Energy balance Bond energy released from food must equal the total energy output  Energy intake = the energy liberated during food oxidation Energy output: Immediately lost as heat (~60%) Used to do work (driven by ATP) Stored as fat or glycogen Heat energy Cannot be used to do work Warms the tissues and blood Helps maintain the homeostatic body temperature Allows metabolic reactions to occur efficiently Obesity Body mass index (BMI) = wt (lb)  705/ht (inches)2 Considered overweight if BMI is 25 to 30 Considered obese if BMI is greater than 30 Higher incidence of atherosclerosis, diabetes mellitus, hypertension, heart disease, and