MCDB 1B - 50 Nutrition, Digestion, and Absorption 50...

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Unformatted text preview: 50 Nutrition, Digestion, and Absorption 50 Animals are heterotrophs : They must obtain their nutrition by eating other organisms. Most plants, some bacteria, and some protists are autotrophs : They trap solar energy through photosynthesis and use that energy to synthesize all of their components. Heterotrophs depend on the organic synthesis carried out by autotrophs. Nutrient Requirements 50 Measuring energy A calorie is the amount of heat needed to raise the temperature of 1 g of water by 1C. 1 kilocalorie (kcal) = 1,000 calories Nutritionists refer to the kilocalorie as the Calorie (Cal) , which is capitalized to distinguish it from the single calorie. Scientists are abandoning the calorie in favor of the International System of Units measure of energy called the joule (1 joule = 0.239 calories). 50 Nutrient Requirements An animals metabolic rate is the measure of the overall energy needs that must be met by the animals food. Fats , carbohydrates , and proteins are the components of food that provide that energy. Basal metabolic rate is the metabolic rate resulting from all of the essential physiological functions that take place in a resting state. Physical activity adds to the basal energy requirement. Figure 50.2 Food Energy and How We Use It ...the time it takes to burn off these foods 50 Energy Stores animals store fuel molecules that can be released as ed between meals. ohydrates are stored in liver and muscle cells as gen . The total glycogen store is about one days y requirements. ost important form of stored energy in animals is at has more energy per gram than glycogen, and it is d with little associated water, making it more act. 50 Nutrient Requirements Animals that do not take in enough food to meet their energy requirements are undernourished . They must metabolize molecules of their own body to provide the energy they need. The first storage compounds to be metabolized in this state are glycogen and fat, so that protein loss is minimized for as long as possible. Eventually, a starving animal must use its own proteins for fuel. This impairs body functions and eventually leads to death (also: remember diabetes mellitus). Figure 50.3 The Course of Starvation Glycogen Fat Protein 50 Nutrient Requirements Animals that take in more food than is necessary to meet their energy demands are overnourished . Excess nutrients are stored as increased body mass. Glycogen reserves are built up, and then additional carbohydrates, proteins, and fats are converted to body fat. Some species use seasonal overnourishment to survive periods when food is unavailable. In humans, however, overnourishment can be a serious health hazard, increasing the risk of high blood pressure, heart attack, diabetes, and other disorders....
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This note was uploaded on 10/08/2010 for the course MCDB MCDB 1B taught by Professor Weimbs,finklestein during the Summer '09 term at UCSB.

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MCDB 1B - 50 Nutrition, Digestion, and Absorption 50...

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