Biol172_chapter41_2009

Biol172_chapter41_2009 - Chapter 41 ANIMAL NUTRITION...

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1 Chapter 41 ANIMAL NUTRITION Glucose Fatty acids Amino acids Nucleic acids H 2 0 CO 2 NH 3 ,urea phosphate ATP ADP catabolism Glucose Fatty acids Amino acids Nucleic acids Starch, cellulose Lipids, wax Proteins DNA, RNA anabolism Why do we have to eat? Chemical energy and the building blocks for growth has to be taken up in the form of complex organic substances As opposed to plants and prokaryotes, which can synthesize these components from inorganic precursors Chemical energy is required for all the cellular work in the body Organic raw materials used for biosynthesis (carbon skeletons) Essential nutrients that the body cannot synthesize e.g. vitamins Largest use of energy is for production of derived from oxidation of organic fuel molecules in cellular respiration Homeostatic mechanisms manage an animal’s energy budget Excess energy can be used for biosynthesis Glucose is a major fuel molecule in cells, and its levels are regulated by hormones Homeostatic mechanisms manage an animal’s energy budget Glucose levels are high during phases high- energy requirement Rapid conversion to ATP Sustained high glucose levels are pathological Normally, glucose is stored in an osmotically inactive form Glycogen in muscles and liver Rapid enzymatic conversion into glucose However: further conversion to fat! Homeostatic mechanisms manage an animal’s energy budget Glucose is a highly desirable but rare nutrient in a “natural” diet Fruit eating birds, bats Necta feeding humming birds Nectar-feeding humming birds
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2 STIMULUS: Blood glucose level rises after eating. Glucose regulation as an example of homeostasis When blood glucose level rises, 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. As a result, blood glucose level drops Figure 41.3 Homeostasis: 90 mg glucose/ 100 mL blood STIMULUS: Blood glucose level drops below set point. When blood glucose level drops, the pancreas secretes the hormone glucagon , which opposes the effect of insulin Glucagon promotes the breakdown of glycogen in the liver and the release of glucose into the blood, increasing blood glucose level Imbalances in the homeostatic mechanisms to
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This note was uploaded on 08/30/2010 for the course BIO 320 taught by Professor Wu during the Spring '10 term at USC.

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Biol172_chapter41_2009 - Chapter 41 ANIMAL NUTRITION...

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