chapt42_lecture Revised

chapt42_lecture Revised - CHAPTER 42 CONTROL OF ENERGY...

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1 CHAPTER 42 CONTROL OF ENERGY BALANCE, METABOLIC RATE, AND BODY TEMPERATURE
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2 http://highered.mcgraw- hill.com/sites/0072437316/st udent_view0/chapter44/ani mations.html
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3 All animals require sources of carbon, nitrogen, and other nutrients Used to assemble macromolecules or generate ATP Animals must have mechanisms to maintain blood levels of important nutrients despite irregular nutrient flow
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4 Metabolism – all the activities and chemical reactions in an animal’s body Metabolic rate – rate at which animal uses fuel to supply ATP for these reactions Metabolism and body temperature are related – heat is generated as a by- product of nutrient breakdown and ATP synthesis
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5 Nutrient utilization and storage
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6 Nutrient utilization divided into 2 alternating phases Absorptive state is the period during which ingested nutrients enter blood and some of these nutrients supply the energy need of the body while the remainder is stored. Post-absorptive state is the period during which the GI tract is empty of nutrients and body stores must supply required energy.
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7 Absorptive state
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8 Absorbed carbohydrates Chief monomers absorbed are glucose, galactose, and fructose Glucose is 1 of 2 major energy sources during absorptive phase (other is fat) Much of absorbed glucose used to synthesize ATP Skeletal muscle major consumer of glucose Excess glucose stored as glycogen in liver or triglycerides in adipose tissue
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9 Triglycerides Too large to diffuse across plasma membrane of intestinal epithelial cells Digested into monoglycerides and fatty acids Diffuse into intestinal epithelial cells Resynthesized into triglycerides Packaged into chylomicrons for blood transport Lipoprotein lipase releases fatty acids to diffuse into cells of the body
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10 Amino acids Excess converted by liver cells into carbohydrate or fat Taken up by all body cells Used to synthesize proteins Excess amino acids not stored as protein
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11 Post-absorptive state
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12 Postabsorptive period No glucose is absorbed from the intestinal tract during this time, yet the blood glucose concentration must be maintained As the absorptive period ends, Synthesis of glycogen and fat slows and breakdown of these substances begins . Can you tell why glucose concentration must be maintained ? Because the brain normally utilizes only glucose for energy . If blood glucose levels fall too low, brain function can be affected, ranging from mental retardation, seizure, coma or even death.
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13 The events that maintain blood glucose concentration fall into two categories: Reactions that provide glucose to the blood Cellular utilization of fat for energy, thus sparing glucose for the brain and nervous system
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14 Vertebrates can increase their blood glucose levels during postabsorptive period in two major ways. Glycogenolysis –
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chapt42_lecture Revised - CHAPTER 42 CONTROL OF ENERGY...

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