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chapter41 - Chapter 41 ANIMAL NUTRITION A balanced diet...

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Chapter 41 ANIMAL NUTRITION A balanced diet provides fuel for cellular work, as well as all the materials the body needs to construct its own organic molecules. Nutrients are substances used as a source of energy, in metabolic processes and as building blocks in the growth and repair of tissues. Nutrition is processes of taking and assimilating food. THE NEED TO FEED Dietary categories: Herbivores feed on plant material and are also known as primary consumers. Carnivores feed on herbivores or other carnivores. They are known as secondary or high- order consumers. Omnivores have a very varied diet of plants and animals. Feeding adaptations: Suspension feeders are omnivores that remove small organisms like algae and minute crustaceans from the water. They feed on plankton. Substrate feeders live in the food source, eating their way through the food, e. g. leaf miners, maggots. Fluid feeders suck nutrient-rich fluids from a living host, e. g. leeches, mosquitoes, aphids. Bulk feeders eat large pieces of food. They use many modified body parts like tentacles, beaks, claws, pincers, etc. HOMEOSTATIC MECHANISMS Animals need food for energy, carbon skeletons to make its own molecules, and essential nutrients, molecules the organism cannot make for itself and must obtain in food. ATP powers resting metabolism, activity and temperature regulation. ATP is derived from the oxidation of carbohydrates, fats and proteins. Glucose regulation When an animal takes more calories than it needs for ATP, the excess can be used for biosynthesis or is stored.
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In humans, the liver and muscle cells store energy in the form of glycogen , a polymer made up of about 120,000 glucose units. 1. Glucose level rises in the blood above a set point. 2. Pancreas secretes insulin . 3. Insulin stimulates cells to take up glucose and liver and muscle cells to store glucose as glycogen. 4. Glucose level drops below certain point. 5. The pancreas secretes glucagon . 6. Glucagon promotes the breakdown of glycogen and the release of glucose into the blood. 7. Glucose level increases again. 8. Normal concentration of glucose ranges between 70 -120 mg/dl. Glucose concentration below 50 mg/dl or above 250 mg/dl is serious, and a physician should be consulted. Undernourishment is a deficiency in calories. Under this condition, the stored fats and glycogen is used up. The body begins to break down proteins for fuel, muscles begin to decrease in size and the brain can become protein deficient. If the expenditure remains more than the intake, death will eventually occur. Overnourishment or obesity results from excessive food intake. When a person eats an excess of carbohydrates, the body increases carbohydrate oxidation. Then fat in the diet tends to be stored.
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chapter41 - Chapter 41 ANIMAL NUTRITION A balanced diet...

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