Nutrition AP Biology Chapter 21

21.14: Overview: A healthy diet satisfies three needs All animals must obtain:  Fuel to power body activites  Organic molecules to build their own molecules  Essential nutrients that the animal cannot make on its own Eating too little or too much food or the wrong mixture can endanger the animals health

21.15: Chemical energy powers the body Every activity your body performs requires fuel in the form of chemical energy Cellular metabolism produces ATP by oxidizing molecules digested from food Cells use carbohydrates and fats as fuel sources  If these are in short supply, the body uses protein The energy content of food is measured in kilo calories  1 kcal = 1000 calories

Metabolic rate:the rate of energy consumption; sum of all the energy requiring bio-chemical reactions over a given time Metabolism must drive several processes such as:  cell maintenance  Breathing  Beating of the heart Basal Metabolic Rate: number of kilocalories a resting animal requires to fuel essential processes Cells store extra energy in various forms  The liver and muscles store energy in the form of glycogen  Also store extra energy as fat

21.16: An animal’s diet must supply essential nutrients Essential nutrients: materials that must be obtained in preassembled form, the animal cannot make them. Four classes of essential nutrients:  Essential fatty acids  Essential amino acids  Vitamins  Minerals Undernourishment: results from a diet chronically deficient in calories Malnourishment: results from long-term absence of one or more essential nutrients from the diet

Essential fatty acids must be obtained from the diet  Example: linoleic acid, used to make some phospholipids for the cell membrane Adult humans cannot make 8 of the 20 amino acids needed to synthesize proteins  Those eight are known as the essential amino acids

21.17: Vegetarians must obtain all 8 essential amino acids Vegetarian diets range from avoiding meat to avoiding all meat by-products such as cheese, eggs and milk. On such a limited diet, people can become protein deficient because they lack certain amino acids Must eat a variety of plant foods that together supply enough of all the essential amino acids

21.18: A healthy diet includes 13 vitamins and many essential minerals Vitamin: organic nutrient that is obtained from the diet but required in minute amounts Water-soluable vitamins include the b complex and vitamin C  B vitamins function as coenzymes; vitamin c is required to produce connective tissue Fat-Soluble vitamins include vitamins A,D,E,and K Minerals: simple, inorganic nutrients required in small amounts Humans require large amounts of calcium and phosphorus to construct and maintain the skeleton See tables A and B (page 444 and 445)

21.19: Do you need vitamin and mineral supplements? A varied diet should provide enough vitamins and minerals It is considered the best source for these nutrients Recommended Dietary Allowances: minimum amounts of nutrients needed each day; determined by a national scientific panel Some people argue RDAs are too low for some vitamins; research is far from complete Unless recommended by a doctor, stay away from megavitamins-supplements that exceed daily recommended doses

21.20: What do food labels tell us? The Food and Drug Administration (FDA) requires various types of information to be given on food labels Several nutrition facts are on food labels:  Serving size of the food is defined  Energy content in calories is listed per serving Food labels emphasize nutrients believed to be associated with disease risks and healthy diets

21.21: the problem of obesity may reflect on our evolutionary past Overnourishment: consuming more food energy than the body needs for normal metabolism; causes obesity Obesity contributes to diabetes, colon and breast cancer and cardiovascular disease Inheritance is once factor in obesity  Leptin-deficiency-leptin is produced by fat cells. As fat increases, leptin levels rise which cues the brain to suppress appetite. Fat hoarding may have been an advantage in the past

Ancient ancestors were hunter-gatherers Natural selection may have favored those that ate more fatty foods when they were available

21.22: What are the health risks and benefits of weight loss plans? Many weight loss plans have focused on reduced intake of carbohydrates Some lose weight quickly on these plans, however, much of the initial weight loss is water loss Gastric bypass surgery reduces the size of the stomach and the length of the small intestine  For very obese individuals Sustainability is major problem with many diets Best way to lose weight is a combination of increased exercises and a restricted but balanced diet

21.23: Diet can influence cardiovascular disease and cancer A diet rich in saturated fats is linked to high blood cholesterol levels which are linked to cardiovascular disease Cholesterol travels through the body in blood lipoproteins Low-density lipoproteins: high blood levels of lipoproteins, generally correlate with tendency to develop blocked blood vessels  High Density Lipoproteins are just the opposite A diet high in saturated fats increase LDL levels  Saturated fats are found in eggs, butter,and most meats

Trans-fats increase LDL levels and lower HDL levels Eating mainly unsaturated fats tends to lower LDL levels and raise HDL levels There may be a link between diets heavy in fats and breast cancer Other foods may help fight cancer, such as fruits and vegetables The American Cancer society recommends eating a variety of healthy foods, with an emphasis on plant sources