1、Energy Metabolism andBody Temperature Energy metabolism n Definitionn The metabolic processes by which energy is made available for the use of the bodyn The main sources of chemical energy are carbohydrates, fats, and protein. (Hypothalamus: the temperature-, and the food intake-regulating system)n
2、The breakdown of organic molecules liberates the energy and ATP synthesis.n The breakdown of ATP serves as the immediate energy sourse for biological work.n Growth, repair, and physical activity.Energy sourcesn Carbohydrates - mainly glucosen Major source: 70 % of the total energyBy the way, average
3、 Americans receive about 15% from protein (4 Calories per gram), 40% from fat (9 Calories), and 45% from carbohydrates (4 Calories)n ATP is synthesized and storedn By glycolysisn By citric acid cycle ( Krebs cycle )n 1g of carbohydrate contains 4 Calories. Energy sourcesn Fat fatty acidsn Major form
4、 of energy storage The storage of fat in the body is much greater than that of glucosen Alternative energy source 1g of fat contains 9 Calories Energy sourcesn Proteinsn The amount of energy provided by proteins is relatively small in human beingn 1g of protein contains 4 Calories n Protein will bec
5、ome the major energy source to maintain the essential vital activities in special conditionsATP: “Energy Currency”n ATP is generated by combustion/consumption of carbohydrates, fats and proteinsn Energy from ATP can be used by the cells for:n Synthesis and growthn Muscular contractionn Glandular sec
6、retionn Nerve conductionn Active absorptionPhosphocreatine: an ATP “buffer”n Phosphocreatine (or creatine phosphate)n is synthesized in the liver n serves as a rapidly mobilizable reserve of high-energy phosphates in skeletal muscle and brain.n Phosphocreatine can anaerobically donate a phosphate gr
7、oup to ADPand to ATP during an intense muscular or neuronal effort. Energy transfern The metabolism of food yields chemical energy and heat.n Heat is the end product of almost all the energy released in the bodyn About 60% of the energy released from organic molecules appears immediately as heat.n T
8、he rest is used for work.n Metabolic raten Total energy expenditure per hourn Normally expressed in terms of the rate of heat liberation during the chemical reactionsn Unit of energy is calorie n Measurement of energy metabolism n Direct calorimetry n Indirect calorimetryHow do we measure energy metabolic rate or energy expenditure?Measurement of energy metabolism n Direct calorimetry
