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In chapter 23, we talked about how foods are digested and absorbed, but what happens to these foods once they enter the blood? Why do we need bread, meat, and fresh vegetables? Why does everything we eat seem to turn to fat? In this chapter we will answer these questions as we examine both the nature of nutrients and their metabolic roles. | 24 Nutrition, Metabolism, and Body Temperature Regulation: Part A Nutrition Nutrient: a substance in food that promotes normal growth, maintenance, and repair Major nutrients Carbohydrates, lipids, and proteins Other nutrients Vitamins and minerals (and, technically speaking, water) Carbohydrates Dietary sources Starch (complex carbohydrates) in grains and vegetables Sugars in fruits, sugarcane, sugar beets, honey and milk Insoluble fiber: cellulose in vegetables; provides roughage Soluble fiber: pectin in apples and citrus fruits; reduces blood cholesterol levels Carbohydrates Uses Glucose is the fuel used by cells to make ATP Neurons and RBCs rely almost entirely upon glucose Excess glucose is converted to glycogen or fat and stored Lipids Dietary sources 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, organ meats, shellfish, and milk products Lipids Essential fatty acids Linoleic and linolenic acid, found in most vegetable oils Must be ingested Lipids Essential uses of lipids in the body Help absorb fat-soluble vitamins Major fuel of hepatocytes and skeletal muscle Phospholipids are essential in myelin sheaths and all cell membranes Lipids Functions of fatty deposits (adipose tissue) Protective cushions around body organs Insulating layer beneath the skin Concentrated source of energy Proteins Dietary sources 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 Proteins Uses Structural materials: keratin, collagen, elastin, muscle proteins Most functional molecules: enzymes, some hormones, antibodies Proteins Use of amino acids in the body All-or-none rule All amino acids needed must be present for protein synthesis to occur Adequacy of caloric intake Protein will be used as fuel if there | 24 Nutrition, Metabolism, and Body Temperature Regulation: Part A Nutrition Nutrient: a substance in food that promotes normal growth, maintenance, and repair Major nutrients Carbohydrates, lipids, and proteins Other nutrients Vitamins and minerals (and, technically speaking, water) Carbohydrates Dietary sources Starch (complex carbohydrates) in grains and vegetables Sugars in fruits, sugarcane, sugar beets, honey and milk Insoluble fiber: cellulose in vegetables; provides roughage Soluble fiber: pectin in apples and citrus fruits; reduces blood cholesterol levels Carbohydrates Uses Glucose is the fuel used by cells to make ATP Neurons and RBCs rely almost entirely upon glucose Excess glucose is converted to glycogen or fat and stored Lipids Dietary sources 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, organ meats, shellfish, and milk products Lipids Essential .
