CH41 - Animal Nutrition Chapter 41 Nutrition For any...

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Animal Nutrition Chapter 41 Nutrition • For any animal, a nutritionally adequate diet is essential for homeostasis , a steady-state balance in body functions. • A balanced diet provides fuel for cellular work and the materials needed to construct organic molecules. • A nutritionally adequate diet satisfies three needs: 1. Fuel (chemical energy) for all the cellular work of the body; 2. Organic raw materials animals use in biosynthesis (carbon skeletons to make many of their own molecules) 3. Essential nutrients , substances that the animals cannot make for itself from any raw material and therefore must obtain in food in prefabricated form. Fuel • Homeostatic mechanisms manage an animal’s fuel – The flow of food energy into and out of an animal can be viewed as an “ energy budget – The production of ATP accounts for the largest fraction of the energy budget of most animals. Adenosine Triphosphate (ATP) • ATP powers basal or resting metabolism, as well as activity, and temperature regulation (in endothermic animals). • Nearly all ATP is derived from oxidation of organic fuel molecules in cellular respiration – Carbohydrates – Proteins – Fats
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Fuel: Carbs, Fats, Proteins • The monomers of carbohydrates, fats, and proteins can be used as fuel, although priority is usually given to carbohydrates and fats. • Protein is generally burned only as a last resort. Fuel • Fats are especially rich in energy, liberating about twice the energy liberated from an equal amount of carbohydrate or protein during oxidation. • When an animal takes in more calories than it needs to produce ATP, the excess can be used for biosynthesis (Growth, Storage and Reproduction). Control of Blood Sugar In humans, the liver and muscle cells store energy as glycogen , a polymer made up of many glucose units. Glucose is a major fuel molecule for cells, and its metabolism, regulated by hormones is an important aspect of homeostasis. If glycogen stores are full and caloric intake still exceeds caloric expenditure, the excess is usually stored as fat. The human body regulates the use and storage of glucose , a major cellular fuel. – When glucose levels rise above a set point, the pancreas secretes insulin into the blood. – Insulin enhances the transport of glucose into body cells and stimulates the liver and muscle cells to store glucose as glycogen, dropping blood glucose levels. – When glucose levels drop below a set point, the pancreas secretes glucagon into the blood. – Glucagon promotes the breakdown of glycogen and the release of glucose into the blood, increasing the blood glucose levels.
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Energy Storage When fewer calories are taken in than are expended, fuel is taken out of storage depots and oxidized. The human body generally expends liver glycogen first, and then draws on
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CH41 - Animal Nutrition Chapter 41 Nutrition For any...

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