Nutrition and Energy 1

Transcription

1 Nutrition and Energy 1

2 Food Energy The ingestion of food serves two primary functions: 1. it provides a source of energy 2. it provides raw materials the animal is unable to manufacture for itself. 2

3 Basal metabolic rate Even an animal at rest requires energy to support its metabolism. The minimum rate of energy consumption under defined resting conditions is called the basal metabolic rate (BMR). The BMR is relatively constant for a given individual, depending primarily on the person s age, sex, and body size. 3

4 Exertion increases metabolic rate Physical exertion raises the metabolic rate above the BMR. If energy taken from food is greater than the energy consumed per day, the excess energy will be stored in glycogen and fats. As glycogen reserves are limited, continued ingestion of excess food results primarily in the accumulation of fat. Food energy is measured in kilocalories (1 kcal = 1000 calories). The measurement of kilocalories in food is determined by the amount of heat generated when the food is burned. The small calorie or gram calorie (symbol:cal) is the approximate amount of energy needed to raise the temperature of one gram of water by one degree Celsius at a pressure of one atmosphere. The large calorie, dietary calorie or Calorie (symbol:cal) is equal to small calories or one kilocalorie.

5 Nutrition Nutrition is the activity by which living organisms obtain raw materials from the environment and transport them into their cells. The cells metabolize these raw materials and synthesize structural components, enzymes and other biologically important substances. A ll the elements and compounds taken into a living thing are nutrients. 5

6 Digestion Animals are heterotrophic organisms, and their nutrients are in the form of organic molecules. These organic molecules rarely come in forms that are readily useful, so animals must process the foods into forms that can be absorbed. This processing is called digestion. 6

7 Nutrition in animals The nutrients used by animals include: carbohydrates proteins nucleic acids lipids minerals vitamins 7

8 Primary Nutrients carbohydrates basic source of energy for all animals. About half of the total calories every animal consumes daily are from carbohydrates. proteins form the framework of the animal body. Although many amino acids can be synthesized, many others must be supplied in the diet. During digestion, proteins are broken down into their constituent amino acids. lipids used to form membranes, the sheaths surrounding nerves and certain hormones. One type of lipid, the fats, are extremely useful energy sources. nucleic acids used for the construction of DNA, RNA and ATP. Animals obtain their nucleic acids from plant and animal tissues. During digestion, the nucleic acids are broken down into nucleotides. 8

9 Essential Nutrients The materials that an animal's cell requires but cannot synthesize are called essential nutrients Minerals mineral nutrients are the chemicals required by living organisms, other than the elements (C, H, N, O) present in common organic molecules. Minerals in order of abundance in the human body include the seven major minerals calcium, phosphorus, potassium, sulfur, sodium, chlorine, and magnesium. Plants absorb dissolved minerals in soils, which are subsequently picked up by the herbivores that eat them and so on, the minerals move up the food chain. Vitamins Vitamins are organic molecules with diverse functions that are required in the diet (13 for humans) in very small amounts. Vitamins are classified as water-soluble or fat-soluble. The term vitamin was derived from "vitamine," a word coined in 1912 by the Polish biochemist Kazimierz Funk. The name is from vital and amine, meaning amine of life 9

10 Major Minerals Required by Humans Mineral Function Main Diary Source Potassium Essential in regulating ATP Legumes, tomatoes, bananas, papayas, lentils, dry beans, whole grains, avocados, soy beans, spinach. Chlorine Production of acids in the stomach and in cellular transport functions. Table salt (NaCl) is the main dietary source. Sodium Essential in regulating ATP Table salt (sodium chloride, the main source), seaweeds, milk, and spinach. Calcium Phosphorus Needed for muscle, heart and digestive system health, builds bone, supports synthesis and function of blood cells. is a component of bones and cells. Functions in energy processing (ATP). Eggs, salmon, sardines, green leafy vegetables, nuts, seeds, tofu. Red meat, fish, poultry, bread, rice, oats. Magnesium Required for processing ATP and for bones. Raw nuts, soy beans, spinach, seaweeds, tomatoes, beans. 10

11 Major Vitamins Required by Humans Vitamin Function Main Diary Source RDA Recommended dietary allowances Vitamin A Used in making visual pigments, maintaining epithelial tissues Green vegetables, milk products, liver 900 µg Vitamin B complex of 8 vitamins Coenzyme in cellular respiration and in many phases of amino acid and nucleic acids production; NAD + and NADP + composition and Coenzyme-A; Cereals, vegetables, meats and legumes from 1 to 100 mg Vitamin C Important in forming collagen, cementum of bone, teeth, connective tissue of blood vessels; may help maintain resistance to infection Fruit, green vegetables 90 mg Vitamin D Increases absorption of calcium and promotes bone formation Dairy products, cod liver oil 10 µg Vitamin E Protects fatty acids and cell membranes from oxidation Margarine, seeds, green leafy vegetables 15 mg Vitamin K Essential to blood clotting Green leafy vegetables 120 µg Vitamin D Vitamin C VitaminB1

12 Vitamins classification 9 water-soluble: B vitamins and vitamin C Water-soluble vitamins dissolve easily in water and, in general, are readily excreted from the body. As they are not stored, more consistent daily intake is important. Many types of water-soluble vitamins are synthesized by bacteria. 4 fat-soluble: A, D, E, and K. Fat-soluble vitamins are absorbed through the intestinal tract with the help of lipids. Because they are more likely to accumulate in the body, generally the RDA is lower and are more likely to lead to hypervitaminosis than are watersoluble vitamins. In large doses, some vitamins have documented side-effects that tend to be more severe with a larger dosage. Often overdosing (vitamin poisoning) from vitamin supplementation does occur. At high enough dosages, some vitamins cause side-effects such as nausea, diarrhea, and vomiting 12