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NOTES- chap 41 - Nutritionally adequate diet satisfies...

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Nutritionally adequate diet satisfies three needs: fuel (chemical energy) for cellular work of the body; organic raw materials animals use in biosynthesis (carbon skeletons to make many of their own molecules); essential nutrients, substances that the animal cannot make for itself from any raw materials and therefore must obtain in food. Glucose regulation as an example of homeostasis in regulation . When an animal takes in more calories than it needs to produce ATP, the excess can be used for biosynthesis. If the animal isn’t growing or reproducing, the body tends to store the surplus in energy depots. . In humans, the liver and muscle cells store energy in the form of glycogen, a polymer made up of many glucose units. The regulation by hormones of glucose is an important aspect of homeostasis. If glycogen stores are full and caloric intake exceeds caloric expenditure, the excess is stored as fat. Undernurishment: an animal is chronically deficient in calories . stores of glycogen and fat are used up . the body begins breaking down its own proteins for fuel . muscles begin to decrease in size . the brain can become protein-deficient anorexia or disruption of food supply result in undernurishment Overnurishment: . results from excessive food intake . human body hoards fat, it tends to store excess fat molecules obtained from food instead of using them for fuel however, with excess of carbohydrates the body tends to increase rate of carbohydrate oxidation - consumption of fat can have a more direct effect on weight than the amount of dietary carbohydrates Regulation of Body Weight complex feedback mechanisms regulate fat storage and use . in mammals, a hormone called leptin produced by adipose cells, is a key part an increase in adipose tissue increases leptin levels in the blood. a high leptin level cues the brain to depress appetite and to increase energy-consuming muscular activity and body-heat production loss of body fat decreases leptin levels in the blood, signaling the brain to increase appetite and weight gain These feedback mechanisms regulate body weight around a fairly rigid set point in some individuals and over a relatively wide range for others Malnourished: . an animal whose diet is missing one or more essential nutrients
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Essential Nutrients . materials that must be obtained in preassembles for because the animal’s cell cannot make them from any raw material . essential amino acids, essential fatty acids, vitamins, minerals Essential Amino Acids . animals can synthesize 20 amino acids, the remaining ones (essential amino acids) must be obtained from food in prefabricated form . protein deficiency (form of malnutrition) occurs due to a diet that lacks sufficient amount of one or more essential amino acids the victims are usually children, who if they survive infancy, are likely to be retarded . plants are “incomplete” whereas animals (meat, cheese, eggs) are “complete” regarding their provisions of essential amino acids .
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