1、Energy Metabolism andBody Temperature Energy metabolism Definition The metabolic processes by which energy is made available for the use of the body The main sources of chemical energy are carbohydrates, fats, and protein. (Hypothalamus: the temperature-, and the food intake-regulating system) The b
2、reakdown of organic molecules liberates the energy and ATP synthesis. The breakdown of ATP serves as the immediate energy sourse for biological work. Growth, repair, and physical activity.Energy sources Carbohydrates - mainly glucose Major source: 70 % of the total energyBy the way, average American
3、s receive about 15% from protein (4 Calories per gram), 40% from fat (9 Calories), and 45% from carbohydrates (4 Calories) ATP is synthesized and stored By glycolysis By citric acid cycle ( Krebs cycle ) 1g of carbohydrate contains 4 Calories. Energy sources Fat fatty acids Major form of energy stor
4、age The storage of fat in the body is much greater than that of glucose Alternative energy source 1g of fat contains 9 Calories Energy sources Proteins The amount of energy provided by proteins is relatively small in human being 1g of protein contains 4 Calories Protein will become the major energy
5、source to maintain the essential vital activities in special conditionsATP: “Energy Currency” ATP is generated by combustion/consumption of carbohydrates, fats and proteins Energy from ATP can be used by the cells for: Synthesis and growth Muscular contraction Glandular secretion Nerve conduction Ac
6、tive absorptionPhosphocreatine: an ATP “buffer” Phosphocreatine (or creatine phosphate) is synthesized in the liver serves as a rapidly mobilizable reserve of high-energy phosphates in skeletal muscle and brain. Phosphocreatine can anaerobically donate a phosphate group to ADPand to ATP during an in
7、tense muscular or neuronal effort. Energy transfer The metabolism of food yields chemical energy and heat. Heat is the end product of almost all the energy released in the body About 60% of the energy released from organic molecules appears immediately as heat. The rest is used for work. Metabolic r
8、ate Total energy expenditure per hour Normally expressed in terms of the rate of heat liberation during the chemical reactions Unit of energy is calorie Measurement of energy metabolism Direct calorimetry Indirect calorimetryHow do we measure energy metabolic rate or energy expenditure?Measurement of energy metabolism Direct calorimetry
